Fujica ST901 — part 3 Product booklet

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Wide-angleand standardlenses

The shorter the focal length of a lens, the wider its angle of view. The Fujinon lenses
 range from a 16 mm fisheye type with an angle of view of 180 degrees to a 1000
mm taking in an arc of no more than 2{ degrees.So the fisheye takes in virtually
 everything in front of  it on a much reduced scale, while the 1000 mm has extreme
 tunnel  vision and magnifies the scale of objects within   its vision beyond the
 capability  of the human eye. Between the two, there are more moderately wide-
 angle lenses,so-called standard or normal focal length lenses and less extreme long-
 focus types.

 Fisheye  lens
 Wide-angle lenses are becoming more popular as they become less difficult to
make. They used to have tendencies toward vignetting (a lack of illumination  in the
 corners of the image) and barrel distortion (an outward curvature of straight lines).
The latter distortion  is still evident, of course, in a fisheye lens. Indeed, it is left un-
 corrected in order to obtain the 180 degree angle, which would be impossible
 without  it. The Fujinon fisheye, however, is of the type providing 180 degree
 coverage on the image diagonal only, so that the whole image area is used. Those
 giving full l80-degree coverage produce a circular image within the frame.
   Wide-angle lenses such as the 28 and 35 mm are useful for those who shoot
 habitudly  in cramped surroundings or who wish to have sufficient depth of field at
 relatively close range to be able to shoot quickly and confidently without constant
 refocusing. They are often also valuable, either for practical purposes or special ef-
 fects,  in  providing  great  apparent  disparity  of  size between foreground  and
background.
  The standard focal length for 35 mm work is generally conceded to be about 50
mm because, at the theoretically correct viewing distance, such a lens gives a
 perspective effect that seems about normal to the human eye. In this range, Fuji
 have 50 mm and 55 mm lenses and a special 55 mm macro type (see page 102).



Angles  of view
The wide-angle and standard lenses range from the 18O-deg angle of the
16mm fisheye to about 42-deg for the 55mm.

           EBG Fujinon wide-angle and rtandard  leneer

 Focal   Angle   Aperture    Min. focue     Filter     Length      Weight
 length         (')    max min   m f t           size   mm     in     g o 2
 {mm}                       mm
  16   180    2.8 22   0.25  0.8    built   55.5   2.2  425   15
                                                                                                           i n
  1 9     96     3.5  22   0.3    1.O    7 7    4 8     1 . 9  264    9.3
  28     7 4     3 . 5  1 6   0 . 4    1 . 3    4 9    3 8 . 5  1 . 5  184    6.5
  35     62.7   1.9  16   0.4     1.3   49    48     1.9  230         I
  35     62.7   2.8  16   0.4     1.3   49    44     1.7  1 8 5    6 . 5
  50     45.4   1.4  16   0.45   1.5   49    43.5   1.7  270    9.5
  55     42.2   1.8  16   0.45   1.5   49    42     1.6  200    7
  55     42.2    3.5  32   0.24   0.8    4 9    5 1 . 5  2    205     7.2

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Long-focuslenses

AU the Fujinon long-focus lenses are of telephoto construction. This means they are
more compact than might be expected.Even the 1000 mm lens is only 715 mm (28
 in) long. "Only"  is a comparative term, of course. It is short compared with its focal
 length, but a lens more than 2 ft long and weighing about  I I lb is not easy to han-
 dle. It needs a stout tripod on a firm foundation to provide the quality image of
which  it  is capable.
   This is true of most long-focus lenses.Although  it is tempting to try long range
 shots of almost invisible subjects, you have little hope of seeing much on the film
unless the camera is kept really still at the moment of exposure. Even then, at ex-
tremely long range you need clear air to shoot through.
 Mounting   unit
The longer-focus Fujinon lenses(400 mm upward) have a tripod mounting ring and
a camera mounting tube. You first mount the lens on the tripod then turn the ring
behind the focusing index to bring its white dot to the top, in line with the mounting
 unit dot and the focusing index. Pull the mounting unit off the lens and screw it into
the camera body. Attach camera and mounting unit to lens by again lining up the
three marks, pushing the mounting unit in and twisting the ring in front of it to the
 right to lock  it. Keep the unit pressed in hard while you turn the locking ring and
make sure that  it locks properly. The mounting ring will not go into the lens if the
locking ring has meanwhile been turned to the right. Turn  it at least a complete turn
to the left to line up the dots.
  The shorter Fujinon long-focus lensesprovide a useful magnification and can be
hand held with reasonable care. The 200 mmf4.5, at only a little over 5 in long and
one pound in weight, gives an image four times greater than that from the standard
50 mm lens and is not too difficult to hold steady. As lensesbecome more compact,
the 200 mm  is gradually replacing the 135 mm as first choice in the long-focus
range. The shorter focal length  still has the advantage of greater speed, however,
while those who use a wide-angle as standard are also catered for by a 100 mm lens
in the Fujinon  range.
Soft-focus   lens
A 100 mm lens is generally very good for portraiture but Fuji are producing a
special lens in the field. The 85 mm f4 has a slightly longer than standard focal
length with an inbuilt degree of controllable  soft focus.
Angles  of view
The range of long focus lenses runs from 85mm to   l OOOmm with angles of
view from 28 to 2.5 deg.
                EBC Fujinon long-focus lensee
 Focal   Angle   Aperture   Min. focur    Filter     Length        Weight
length         ('l   max min  m         ft   m m m m i n g                   oz
   85   28.6   4    1 6   1     3.3   49     64.5    2.5  285    10
  100  24.4   2.8 22   1 . 2   4     49    60      2.4  254      9
  1 3 5  1 8    2.5 22   1 . 5   5    58    80      3.1   432     15.2
  1 3 5  1 8    3.5 22   1 . 5   5    49    79      3.1  300    10.6
  200   12.3   4.5 22   3.5       I     4 9   1 3 3      5.2  489     17.2
  400    6.2   4.5  45   8 2 6        49   289     11.4 1925    68
  600    4     5.6 45  12.5  41    49   410     17.3 3000   106
 1000    2.5   8 4 5     30    98     4 9   7 1 5    28   4960   175

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EBC Fujinonzoom lenses

 There is still a great deal of discussion about the merits'and advantages of zoom
 lenses.They used to be difficult to make without some sacrifice of quality compared
 with lenses of a single focal length. The ability to maintain focus throughout the
 range of focal lengths provided was also suspect.These suspicions must still remain,
 particularly as regards the quality of the image. Sharpnessis now usually more than
 adequate but  it is not uncommon to find barrel or pincushion distortion more ap-
 parent in a zoom than in a prime lens.
  The advantage of the zoom in versatility is undisputed but you have to accept a
 restriction on maximum aperture and minimum focusing distance and a not incon-
 siderable bulk. The Fujinon 541270 mm lens, for example, is a remarkable achieve-
 ment but at the short end it is a standard lens with a maximum f4.5 aperture, 2.5 m
 (6 ft) minimum focus and a weight of about 3+ lb. Even at the long end, its 70 mm
 extra focal length compared with the 200 mmf4.5 costs 90 mm in length and more
 than 2 lb in weight.
  The 75-150 mm is more manageable and provides a useful range of focal lengths
 at about half the weight of its bigger brother.
     It  is in zoom lenses and other multi-element lenses that Fuji's electron beam
 coating (EBC) is so valuable. Multi-coating has attracted a great deal of attention in
 recent years although it has been standard practice on specialist lenses(particularly
 for television) for a considerable time. The advantage with most lenses is minimal
 but when you have 15 glass elements in 12 groups, as you have in the Fujinon
 5+270 mm zoom, losses by  internal reflection would be significant without
 specialised coating techniques such as the Fuji EBC system. Key elements are
 coated with up to  l  l layers of special materials to reduce reflections from their sur-
 faces and thus to improve picture sharpnessand colour balance. Flare, causing sub-
dued colours and even colour distortion can be significantly reduced by these
 methods. Exceptionally, the 7-element 43-75 mm zoom is not multicoated.





Angles  of view
Zoom lenses have the advantage of continuously variable angles of view.

                  EBG Fujinon zoom lenser

   Focal      Angle    Aperture  Min. focur    Filter   Length     Weight
   length   max   min  maxmin  m        ft    rize  m m i n g o r 2
 min  max      ("1                 mm
   (mml

43    75  53  32   3.5  22  1 . 2   4 4 9        5 8   2 . 3  3 1 5   1 1 . 1
75   150  32  16.4 4.5  22  1 . 8   6 6 2      143   5.6  748   26.4
75   205  32   12.3  3.8  22  2      6.6   62   180   7.7  925   32.7
54   270  43.7  9.2  4.5  22  2.5   8 8 2       220   8.7 1464   5 1 . 6

9E

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Taking inexpensiveclose-ups

 One of the great advantagesof the single-lens-reflexdesign is that it allows you to
 get really close to your subject with the absolute minimum of equipment. When
 the camera lens is positioned one focal length from the film,  ii focuses distant
 objects. To focus closer, you move the lens farther away from the film. There is,
 though, a limit to the travel that can be built in to a iens mount.

 Extension  tubes
 It is a simple matter on the other hand, to take the lens off the camera and put in a
 spacer tube to increase the separation between lens and film. Fuji supply a set of
 three such tubes, known as extension tubes, in 9.5, 19 and 28.5 mm lengths. There
 are also many types available from independent manufacturers. The tubes can be
 used with any lens but a given tube length provides greater magnification when used
 with a lens of shorter focal length. Using all three tubes behind a 55 mm lens, you
 can obtain a magnification of 1.18 (a little more than life size). With a 35 mm lens,
 magnification reaches 1.72. With a 135 mm,  it is only 0.53.
   The tubes have automatic diaphragm mechanisms but no aperture teller. Meter-
 ing has to be carried out in the stopped-down mode on all models. You will find that
 added extension means extra exposure, and a less bright viewfinder image.

 Clore-up   lenrer
 Although extension tubes provide a simple means of working at close range, there
 is a still simpler method. It does not call for extra exposure and therefore often
 allows you to use relatively fast shutter speeds.This method uses close-up or sup-
 plementary lenses.
    Fuji supply only one close-up lens, allowing you to focus from about 1l in out to
 19 in from the front of the close-up lens when you attach it to a camera lens. The
 focal length of the camera lens does not affect the focused distance but  it does af-
 fect the image size in the normal way.
   Close-up lenses are generally supplied in filter mounts that screw into the front of
 the lens. As most Fujinon lenseshave the popular 49 mm thread, you can easily ob-
 tain close-up lensesof various strengths to allow you to shoot at really close range.
  The quality obtainable with close-up lensesis surprisingly good but they are sim-
 ple lensesand it is advisable to stop the camera lens down as far as possible to avoid
 using the marginal rays and to increase depth of field. Full-aperture metering can be
 carried out in the normal way.

 Avoiding  camera  movement
 With all close-rangework, the camera must be rigidly supported becausefocusing is
 critical and depth of field is limited - even at very small apertures. Use a tripod or
 other firm support and a cable release to operate the shutter. As an alternative to
 the cable release, for static subjects, you can use the self-timer to allow camera
 vibrations to settle before the shutter is released. As very long exposures are set
 automatically on the ST90l, an eyepiece shutter is fitted to prevent light entering
 the eyepiece and possibly affecting the exposure. The shutter is operated by a smal
 lever to the left of the viewfinder eyepiece.
 Simple  close-upe
 A The Fuji extensiontubes are in a set of 9.Smm (No 1), 19mm (No 2) and
 28.5mm (No 3). B Close-uplensesare generallysuppliedin powers of 1 ,2 and
 3 dioptres, giving progressively larger images from croser range.

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More sophisticatedclose-ups

 Extonsion  bellows
An extension bellows uses the same principle as tubes by adding extra extension
behind the lens but  it allows you to vary the extension continuously throughout the
length of the collapsible bellows. Fuji provide a bellows of their own manufacture
that gives, with a 55 mm lens, a range of magnifications from 0.61 to 2.32. The
bellows is a simple but sturdy type giving a minimum extension of about 32 mm and
a maximum of about 128 mm. The rail, which carries a scale of extensions, is
mounted on a focusing block so that the required extension can be set and focusing
carried out by moving the complete set-up back and forth.
  To attach the bellows to the camera, you loosen the screw securing the camera
mounting ring, which can then be removed and screwed into the camera body. You
then push the camera body on to the bellows and tighten the screw. Be careful when
removing the bellows. As you loosen the screw, the bellows falls off.
  The lens is mounted on the front of the bellows in the normal way but it does not
lock. The bellows has no full-aperture metering or auto diaphragm facilities. As you
mount the lens, however, the auto-diaphragm pin is pushed in, converting the lens to
a manual type.
  You meter with the lens stopped down and, on the full-aperture-metering models,
you must press the stop-down button on the camera front to obtain a correct
reading, even though the lens is already stopped down.  If you do not, the meter
recommends much more exposure than you really need. It is best to lock the stop-
down button in when using the bellows.

Reversing  the  lens
Camera lensesoften given better results when they are reversed on bellows or tubes,
so that the back of the lens faces the subject. Fuji supply a reverse adapter for this
purpose. It screws into a filter thread of the camera lens and into the 4i mm thread
of the lens mounting flange on camera, tube or bellows. There is also aLeicamount
adapter for lenses with Leica thread.

Using a macro  leng
There is one type of lens that is designed specifically for close-rangework as well as
normal photography. This is the so-called macro lens. The Fujinon macro lens is of
55 mm focal length and has extra extension built into its focusing travel to allow it
to focus to 24 cm, where it provides an image about half life siie. The size of the
image is indicated directly on the lens distance scale.
  The lens is also provided with an extension tube allowing life-size reproduction.
In this case, the image size is indicated on the front of the focusing ring. Without the
tube the lens can be used for full-aperture metering. With  it, you hauJto meter with
the lens stopped down. In both cases, however, it retains automatic diaphragm
operation.
Glose-up  equipment
A  Fuji Extension Bellows.
1 Cameramounting ring.2 Securingscrew.3 Bellows.4 Lens mount. 5 Focus-
ing knob. 6 Extension scale. 7 Front standard clamp. 8 Focusing slide clamp.
B Fujinon 55mm macro lens.
1 Magnification with tube. 2 Focusing ring. 3 Magnification without tube. 4
Depth of field scale.5 Aperture setting.6 Extensiontubefor 1:1 reproduction.
7 Auto diaphragm pins.

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Working at ultra close range

 Camera lensesare not well suited to really high-magnification work. This is the field
 of the microscope and photography of minute objects is best carried out with the
 microscope objective substituted for the camera lens. Fuji supply a microscope
 adapter for this purpose.

 Microscope   adapter
 The adapter is an orthodox design with an extension tube to attach to the camera
 lens mount (the camera lens is not used) and a connecting ring attached to the
 microscope drawtube into which is slipped the microscope eyepieceor a light-shield
 tube when the eyepiece is not used.
   The extension tube is fitted to the camera first and the connecting ring is clamped
 to the microscope drawtube after removing the eyepiece.The eyepiececan then be
 replaced or the light-shield tube can be substituted for it. The instructions tell you to
 insert the light-shield tube from the top but it appears, in fact, that it has to be inser-
 ted in the microscope tube before attaching the connecting ring. The camera and ex-
 tension tube are then attached to the connecting tube by means of the connecting
 ring and the set-up is ready for use. A right-angle finder is useful for viewing and
 focusing.

 Macrocine   copier
 An  exceptional piece of close-range equipment for the Fujica cameras is the
 Macrocine Copier, designed for copying 8 mm or 16 mm cine frames on to the full
 35 mm frame. Essentially it consists of a very small lens designed to work at an
 only slightly variable object distance but with provision for variable extension to
 provide different magnifications. The extension is provided by two tubes, both of
 which are used to enlarge an 8 mm frame to 35 mm, and a short helicoid for fine
 focusing. The film or other translucent item to be copied is held at a fixed distance
 from the lens (apart from the short helicoid travel) by a tubular copy head closed by
 a flat polished plate at the end with an 8 x l1 mm aperture. Spiung arms on thii
 plate hold interchangeableaperture plates for 8 mm or 16 mm films, which are slid
 b-etweenthe                  plate,and the aperture plate. The arms can also hold microscope            !9ad
 slides or similar material.
   Copying is carried out by pointing the camera with the unit attached toward a
 source of bright light, preferably sunlit sky. Metering can be effected by the camera
 meter but you can experiencedifficulty in seeing the needle of the 605 and 705. At
 the greater magnifications, exposure is very long unless powerful lamps are used
 and even the meter of the ST90l may not be able to cope. It might be beiter to put a
 diffuser over the movie frame and expose to electronic flash. You will then have to
 experiment to find the correct exposure.
  The tubes supplied with the Macrocine Copier are of 19 and 28 mm focal length
 and can be used for close-ups with other lenses. They have no auto diaphgrim
 mechanism.
Ultra  close-up  items
A Microscope adapter.
1 Extensiontube. 2 Connecting tube. 4 Light shield tube. 5 clamp. 6 con-
necting ring. 7 Microscope eyepiece. 8 Microscope tube.
B Fuji Macrocinecopy
1 M-1 adapter ring. 2 M-2  adapter ring. 3 Focusing ring. 4 copier head. 5
Aperture plate 8. 6 Aperture plate 16.

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UsefuI accessories

 Eyepiece attachments
 The lens in the viewfinder eyepieceis a weak negative type so, if you are rather long-
'sighted, you might find  it difficult to see the screen image clearly. Then you can
 have the lens changed to a positive type. Or,  if you are very shortsighted and prefer
 to take your spectaclesoffto use your camera, you may like to change the lens for a
 stronger negative type. Fuji supply replacement lenses of +2, +0.5, -2.5  and -4
 dioptres.
     If you prefer to retain your spectacles,you will certainly find the rubber eyecup
 useful, especially with the ST90l and 801. It prevents light creeping past your eye
 into the viewfinder and dimming the LED readings with flare. It protects your spec-
 tacle lenses, too.
  A further accessory to attach to the viewfinder eyepiece is the rightangle finder.
 This is a small, telescope-likeattachment that can be rotated to allow you to view
 the whole screen image from above, below or to the side. It shows a laterally rever-
 sed image, which is a little off-putting when metering with the ST90l and trying to
 read the shutter speeds backward.
    All the eyepiece accessoriesare in two versions, becausethe 5T605 and 705 and
 the AZ-l  have rectangular eyepieceswith grooves into which the attachments slide
 -  leaving the eyepiece lens in place. The ST80l and 901 have screw-in eyepiece
 lenses that are removed for replacement or to  fit the rightangle finder.

 Other  accessories
 Among the other accessoriessupplied are lens hoods (also known as sunshades).
 The longer-focus lenses and zooms are supplied with hoods that slide forward for
 use. The fisheye has a very truncated hood attached. Accessory hoods are available
 for the 135, 100, 55, 50, 35 and 28 mm lenses.the last-mentionedbeine a rec-
 tangular type.
   More vital, perhaps, are the lens caps and body caps supplied for all models and
 lenses.If you put your camera away with no lens attached, you run at least a slight
 danger of damaging the mirror. The body cap is designed to prevent that and to
 keep dust and other foreign bodies out of the camera. Similarly, any lens that is not
 in use should have caps back and front to protect the glass surfaces and the stop-
 down pin on the back of the lens mount.
    All the cameras are supplied in so-called ever ready cases. Fuji's are no worse
 than others but they are clumsy and most people prefer to keep them for transport
 and storage rather than struggle with them while actually using the camera.
    Fuji do not supply filters for their lensesexcept in the case of the 16 mm fisheye,
 which has four filters built in. Most of the Fuji lenses take 49 mm threaded filter
 mounts, however, so you have no difficulty in getting filters of various manufac-
 tures. You can even use the same size with the very long-focus lenses.They screw
 into the front of the lens mounting unit and are thus used behind the lens.





106

Filtersand screens

          Filters for mounting on camera lensesmust be of the highest optical quality. There
           is no point in buying a specially coated lens accurately made from selectedhigh qua-
             lity glassesand then fitting over it a filter little better than a piece of window glass.
         Optical quality gelatin filters are ideal for occasional use, but are too delicate to
       be used continuously. For constant use glass filters (often a gelatin filter cementedV,  between two piecesof glass)are essential.Filters manufactured ficr fitting over light
        sources (either photographic or theatrical) or in colour enlarger heads may pro-
        duce distorted or degraded pictures if used on the camera. Intentional distortion
       may be introduced by using a dirty filter, or specially constructed lens attachments
       and screens.By such means,you can produce blurred images,flare, stars from bright
         points, multiple images and many other effects. Together with  brightly coloured
           filters, these attachments play an important part in creative photography, but care
        should be taken to avoid accidentally emulating  their effects. You should be
         specially careful of the condition and quality of a UV  filter  if, like many photogra-
         phers, you keep it permanently in place.
          Glass filters are supplied in rims which screw into the filter threads on the front
          of the lenses.The rims are manufactured in a standard range of sizes to suit most
         lenses.Adapter rings are available to allow the use of larger filters on lenses with
         smaller filter threads. Becauseof the standardization, you may be able to use one
            filter on severallenses,thus justifying the expenseof buying a top quality filter.
         As filters reduce the light reaching the film, they usually necessitatean increase
           in exposure time (or lens aperture). This increase is given as the factor by which the
        exposure time should be increased.
          Aperture alterations can be calculatedfrom this factor. Thus, for example, a 2x
            filter requires twice the exposure time or one stop larger aperture etc. Some manu-
         facturers also give exposure increasesin thirds of a stop. The simplest way of using
        these with a separateexposure meter (or one built into the camera which uses its
       own light window) is to decreasethe film speedsetting by one unit for each i stop.
       Thus a J stop increasewould need an alteration from 80 ASA (20 DIN) to 50 ASA
        (18 DIN). Cameras with built-in through-the-lens meters also read through the
            filter, and thus give the correct exposure without any modification to the film set-
          ting. The meter can be used in its normal way.

         Filters for black-and-white   film
      When they are used with black-and-white films UV and polarizing filters reduce
        haze and reflection respectively,just as they do with colour films. Coloured filters,
        however, aflect the relative tonal rendering of different coloured parts of the subject.
       Becausea filter acts by reducing the passageof light of complementary (opposite)
         colour, it reducesthe image density produced on the negativefrom an object of that
         colour. The object thus comes out darker in the final print. If-as   is usually the
        case-the cameraexposureis increasedto take account of the light absorbed by the
             filter, objects the same colour as the filter will be rendered lighter than normal in
         the final print.
         The complements of red, green and blue are cyan (blue-green),magenta (red-pur-
          ple) and yellow respectively;intermediatecolours have intermediatecomplements.
       From this you can work out the colour of filter you need to give particular emphasis
          to any part of the subject.Yellow filters are widely used to darken blue parts of the
         subjects-in particular blue skies to emphasisewhite clouds.
          Without any filter, blue parts of a subject tend to be rendered somewhat lighter
         than we see them becauseblue light tends also to contain some ultra-violet radia-

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 tion, to which the film  is sensitive, and the eye is not very sensitive to blue light.
 For this reason, a medium yellow filter may give a more natural tone rendering on
 panchromatic filrn, and is sometimes called a correction filter. The effect may be
exaggeratedby using a dark yellow or orange filter, or for greatest exaggeration
a red filter. Such filters give increasingly darkened skies, with clouds standing out
 dramatically. The accepted "correction" filter for use with tungsten light is a yellow-
green colour.
  Becausehaze tends to reflect blue light and ultra-violet radiation  in preference
 to green or red light, the use of yellow, red or orange filters can reduce its effect
on the film. Deep red filters give the strongest haze penetration, but require con-
 siderable exposure increase,and of course affect the overall tonal rendering of the
photograph.
   Neutral density filters, naturally, do not affect the tone rendering. They simply
allow you to increasethe aperture or lengthen the shutter speedwithout overexpos-
 ing the film.

Filters for colour photography
Filters are used in colour photography to alter the colour balance of the image on
the film. Their use is mainly confined to reversal films because the colour balance
of a print can be determined at the printing  stage. Polarizing and ultra-violet
absorbing filters, however, are commonly used with negative films as well.
   Polarizingfilters.The effect of a polarizing filter is the same with all types of film.
 It can-in  some c.ircumstances-reduce reflections;and can darken a blue sky, with-
out otherwise altering the balance in a colour picture.
   Light coming directly from the sun or other light source is not polarized: the rays
vibrate in all directions. Sometimes, however, light can be restricted to rays all
vibrating in one plane. It is then said to be polarized. For the photographer there
are two important polarizers: polarizing filters, which restrict the passageof all light
not vibrating in their plane of polarization; and smooth reflective non-metallic sur-
faceswhich polarize light reflected at certain angles.Although polarizing filters may
be fitted over light-sources for special applications, they can normally be regarded
as camera fitments used to take advantage of light polarized by reflection.
  The most common use is in restricting the passageof polarized light, thus reduc-
ing its influence on the film. From certain angles this can result in a dramatic reduc-
tion in reflections from glass,water and similar substances(but not from metal sur-
faces).A special instance of this is the blue light reflected from the sky on a sunny
day. An area of the sky at right angles to a line from the sun to the camera position
polarises the sun's rays strongly, and thus careful use of a polarizing filter can selec-
tively darken a blue sky in a colour picture.
  The effect of a polarizing filter depends on its orientation to the polarized light.
It passesalmost all light polarized parallel to its polarizing plane, and is opaque
to light polarized at right angles.
  To simplify their use,polarizing filters for camera useare usually supplied in rota-
table mounts. With a single lens reflex camera, you simply view the subject and
rotate the filter until you seethe effect you want. Some types also have a small extra
filter on the rotation handle.This allows you to check the polarizing action indepen-
dently of the main filter. Polarizing filters require an exposure increase of about 2j
times(lj stops).
  U ltra-uioletfilters. Ultra-violet absorbing (UV) filters reduce the effect of atmos-
pheric haze which would otherwise be exaggeratedbecausephotographic emulsions
are sensitiveto ultra-violet radiation (which is invisible to the eye). The radiation
is scattered strongly by haze and records on colour film as a blue veiling of distant
objects.

l0t

With colour reversal film an ultra-violet  filter has the same haze-cutting effect,
         and also reduces the blue cast sometimes frcund in transparencies taken close to
          large reflecting massessuch as water or snow. Such filters require no exposure in-;lt          crease.
              Skv-li.c1htfi/rers. Skylight filters are ultra-violet absorbing filters coloured a pale
        salmon or iore. Theyari  used with reversal films to give slightly warmer colours
            in transparencies,as well as the nornral UV  filter effects.They require no exposure
          increase.and are a more useful alternative to plain UV filters.
             Colottr conuersiottfilters.To obtain a normal colour balance when using a colour
          reversalfilm with a light source other than that for which it is intended to be used,
         you must use a coloured filter. Filters designedfor this purpose are known as con-
          version filters. Many manufacturers supply them for using commonly available
           film types in normal types of illumination. In general, filters for use wrth daylight
  *         fifins aie blue in colour, and those for use with artificial light films are orange. The
             filters aFe Rormally used on the camera lens, but are equally effective when used to
              filter the light-source.If you are to use two light sourcesof different colour tempera-
           tures.one of them must be filtered to the colour of the other.
            Colour balancing.filters. For special effects and for accurate colour matching,  it
        may be necessaryto change the colour balance slightly. Manufacturers supply two
          types o[filter which are suitable: special pale filters designed for the purpose, and
             filiers designed for colour printing. Almost invariably the necessityfor particular
             filters can be determined only by testing. and information should be sought from
          the fi lter manufacturers.
            Neutral densitt,.filters.Neutral density filters (or attenuators) reduce equally the
          transmission of all wavelengths of the visible spectrum. They come in two forms
          -plntographic'  siluer density,which is simply accurately exposed and developed
            film; and dyedfilters-often using colloidal carbon. Becauseof its high light-scatter-
           ing effect,silver density is not suitable for use over the camera lens. Dyed neutral
          density filters are, however, intended ficr this purpose, and can be used to produce lf          high quality images.
              N.1itral density filters do not affect the colour balancewhatever film they are used
           with. They simply allow the lens aperture to be widened, or the shutter speedlength-
         ened,whiie restricting the exposure to its normal level. They are normally available
            in a range of densitiesfrom 0.1 to 4.0 (transmitting from 80/. to 0.01\  of the avail-t*          able light)with  filter factors varying from just over  I to 10,000.A density between
          1.0 and 2.0 (10"i"-l lzi transmission)enables you to use full aperture in bright sun
          with medium speedfilms. A density of 3.0 (0.1% transmission)allows exposuresup
            to 30 sec under the same conditions.





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    Glossary

          Aberration.   Failing in the ability of a lens to produce a true image.There are many
          forms of aberration and the lens designercan often correct some only by allowing
          others to remain. Generally, the more expensivethe lens,the lessits aberrations.
         Angle  of  view. The extent of the view taken in by a lens. For any particular film
             sizelit varies with the frccallength of the lens. Usually expressedon the diagonal w,w:;
  #,        of the image area.
          Aperture.   The opening in the lens, usually provided by an adjustable iris
   4:      diaphragm, though which light passes.See Limiting aperture, Effective aperture,
   ;iiv,     y'number.
          Aperture   priority.  Automatic exposuresystem in which the lens aperture is set
      il.&::ww      bystop-downthe photographer,mode with andany lensthe camerathat doessetsnottheinterfereshutterwithspeed.the Canmeteringbe usedsystem.in the     *&.'
    &Er;        Artificial    light.  Light from a man-made source, usually restricted to studio,
  Si      photolamp and domesticlighting.When usedto describefilm (also known as Type A
           or Type B) invariably means thesetypes of lighting.
        ASA.  Film speedrating defined by the American National Standards Institute.
         Automatic    iris. Lens diaphragm which is controlled by a mechanism in the
  I        camera body coupled to the shutter release.The diaphragm closes to any preset
          value before the ihutter opens and returns to the fully open position when the*;,fF           shutter closes. t '
          Balanced.  Description applied to colour films to indicate their ability to produce#,v,;tfi,      acceptablecolour responsein various types of lighting. The films normally available
 : #:,   ::.::     are balanced for daylight (5500-6000K), photolamps (3400K) or  studio lamps
        (3200K).
                                                                       meters                                                                                   in exposure  'a-w'                                                        materialused                                           conductive                              (CdS). Photo                     sulphide        Gadmium |   \i,                                                                             resistance                                                                                     Its electrical                                                 blue photocells.                                            or silicon                           to selenium.based         as alternative  i i  e \'  &;  ..        .,tj?+:      decreasesas the light falling on it increases.Cds meters use current from an external   \
         power source, such as a batterY.   t|  {,i.::Zi:
  i  &i:'
        Camera  shake.  Movement of camera caused by unsteady hold or support,
            vibration, etc., leading, particularly at slower shutter speeds.to a blurred image
         on the film. It is a major causeof unsharp pictures,especiallywith long focus lenses.
  *
          Gapacitor.   Electrical component once more commonly known as a condenser'
          Stores electrical energy supplied by a power source and can discharge it more
           rapidly than the source itself. Used in flash equipment, providing reliable bulb
             firing even from weak batteries, and supplying the surge needed for electronic
           flash tubes.
          Cassette.  Light-trapped film container used with 35 mm cameras.
           Cast. Abnormal colouring of an image produced by departure from recommended
  *,i,     exposure or processing conditions with a transparency film, or when making a
            .oiour print. Can also be caused by rellection within the subject as from a hat on to
           the face.
. i          Click  stop.   Ball bearing and recess or  similar construction used to enable
           shutter speeds,aperture values, etc. to be set by touch.
                                                                 rt3

Colour  negative.  Filnr designedto produce colour image with both tones and
 colours reversedfor subsequentprinting to a positive image,usually on paper.
 Colour  reversal. Film designedto producea normal colour positiveimageon the
 film exposedin the camerafor subsequentviewing by transmittedlight or projection
 on to a screen.
 Colour  temperature.   Description of the colour of a light-sourceby comparing
  it with the colour of light emitted by a (theoretical)perfectradiator at a pariiculai
 temperatureexpressedin kelvins (K). Thus "photographic daylight" has a colour
 temperatureof about 5500K.Photographictungstenlights havecolour temperatures
 of either 3400K or 3200K dependingon their construction.
 Component.   Part of a contpound lens consisting of one element (single lens)
 or more than one element cemented or otherwisejoined together. A lens may
 therefore be described as 4-element, 3-component when two of the elements are
 cementedtogether.
 Computer   flash.  Electronicflash guns which sensethe light rellectedfrom the
 subject. and cut  off their output when they have received sufficient light  for
 correct exposure. Most  units must be used on  or  close to  the camera for
 direct  lighting  only, and the camera lens must be set to a  specific aperture
 (or a small range of apertures)determinedby the speedof the film in use.
 Condenser.  Generallya simple lens used to collect light and concentrateit on a
 particular area,as in enlarger or projector. Frequently in the form of two plano-
 convex lenses in a metal housing. A condenser, normally of the fresnel type, is
 usedto ensureeven illumination of the viewing screenson SLR cameras.
 Contrast.  Tonal difference.More often usedto compareoriginal and reproduction.
 A negative may be said to be contrasty if  it shows fewer, more widely spaced
 tones than in the original.
 Delayed  action. Mechanismdelayingthe openingof the shutterfiorsome seconds
 after the releasehas been operated. Also known as serf-timer.
 Depth  of  field. The distancebetweenthe nearestand farthestplanes in a scene
 that-a-lenscan reproducewith acceptablesharpness.Varies with effectiveaperture
 (and thus with focal length at any particular .fnumber) focuseddistance and the
 standardsset for acceptablesharpness.
 Developer.  Solution used to make visible the image produced by allowing light
 to.      on the light-sensitivematerial. The basic conitituent is a developing agent    lall
which reducesthe light-struck silver halide to metallic silver. Colour dev-elolers
includechemicalswhich producecoloured dyes coincidentallywith reduction of the
silver halides.
Diaphragm.  Deviceconsistingof thin overlappingmetal leavespivoting outwards
to form a circular opening of variable size. Used to control iight t.insmission
through a lens.
DlN.  Filnr speed rating defined by the DeurtscherNonnenausschuss(German
standardsorganisation ).
Effective  aperture.  The diameter of the bundle of light rays striking the Iirst
lens elementthat actually passthrough the lens at anygivin dizrphragmsEtting.
Electronic    f lash. Light sourcebasedon electricaldischargeacrosstwo electrodes
in a gas-filledtube. Usually designedto provide light approiinrating to daylight.

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          Element.  Single lens used in association with others to form a compound
           construction.
          Emulsion.  Suspensionof light-sensitivesilver salts in gelatin.
         Exposure. The act of allowing light to reach the li-eht-sensitiveemulsion of the
          photographic material. Also refersto the amount (duration and intensity)of light
          which reachesthe film.
         Exposure  factor. A figure by which the exposureindicatedfor an averagesubject
          and,,orprocessingshoulibernuttiptl.d to allow for non-averageconditions.Usually
            ,,ppii.d'to filters]occasionallyto iightlng. processing.etc. Not normally used with
          through-the-lensexposuremetcrs'
         Exposure  meter.  Instrumentcontaininglight sensitivesubstancewhich indicates
          apertureand shutter speedsettingsrequired'
          Extension  bellows.  Device used to provide the additional separationbetween
           lens and film requiredfor close-upphotography.Consistsof extendiblebellows and
          mounting plates at front and reai to fit the lens and cameritbody respectively'
          Extension  tubes.  Metal tubes usedto obtain the additional separationbetween
           lens and film for close-upphotography.They are fitted with screwthread or bayonet
         mounts to sr.ritvarious lens mounts.
           f-number.  Numerical expression of  the  light-transmitting power of  a  lens'
          Calculatedfront thc tocal length of the lens divided by the diameter of the bLrndleof
             tignt .oy, enteringthe lens aid passingthrough the aperttrrein the iris di^phragm'I+           Film base. Flexible support on rvhich light sensitiveemttlsionis coatecl.
              Filter. A pieceof material which restrictsthe transmissionof radiatiorr.Gencrally'
          coloured to absorb li_chtof certuin colours. Can be used over light sottrcesor ovcr
           the camera lens. Camera lens filters are ttsuallyglass- either dyed or saldwichin-tr
           a pieceof gelatin-in a screw-infilter holdcr'
          Fisheye  lens. Ultra-wide anglelens giving lll0 angle of view' Basicalll'produces
           a circular image- on 35 mm. 5-9 n'ti't l.nt..  showin-ewhole irnage' 15-17 mm
           lenses-eivingu ,..,ungular image fitting just inside the circle, tftus representing
          180 ilcrossthe diagonal.iAttlwn ilFI
            Fixer.  Solution. usually based on sodium thiosulphate.in which films or prints
           are immersed after devllopment to convcrt the unexposedsilver halides in the
          emulsion to soluble products that can be washed out' This prevents subsecltteut
            deteriorationo[ the image.
           Flashbulb.  Light source based on ignition*sizes  of combttstiblenretal wire in  rt gas-
               filled transpirrentenvelope. Popular      are r'rsuallyblue-coated to give light
           approximatingto daYlight.
           Flashcube.   Self-containedunit comprising fgttr small llashbtrlbs witlt own
             rellectors.Designedto rotate in specialcametn socket as filrll is wound on' can
          be used in a splciarladapter on ci merus without the socket. but will not rotateffifl            automaticltllY.ffi
           Focal  length.  Distatncefrom a lens to the imttge it prodtrcesof a very distant
             subject.With a .o1npounOlens the point fronr u'hii'h it is nlertsureddependson the
            construction o[ the lens. It is within the lc-nsrvith those of normal constructiott,

                                                                                                                                                                                                       l l 5

 {:l

but may be in front of telephoto lenses,or behind inverted telephotos. Whatever
the lens construction, the focal length determinesthe size of the image formed.
Focus.  Generally, the act of adjusting a lens to produce a sharp image. In a
camera, this is effectedby moving the lens bodily towards or away from the film
 o-. by moving the front part of the lens towards or away from the rear part, thus
 altering its focal length.

Format.  Shape and size of image provided by camera or presentedin final print
 or transparency.Governed in the camera by the opening at the rear of the body
over which the film passesor is placed. The standard 35 mm format is 36 x 24 mm:
half-frame, I 8 x 24 mm: 126 size, 28 x 28 mm;   I 10, l7 x l3 mm; standard rollfilm
(120 size),2* x 2I in.
Fresnel.  Pattern of a special form of condenser lens consisting of a series of
concentric stepped rings, each being a section of a convex surface which would,
 if continued, form a much thicker lens. Used on focusing screens to distribute
image brightnessevenly over the screen.
Full aperture  metering.  TTL meteringsystemsin which the camerasimulates
the          of stopping down the lens when the aperture ring is turned, while leaving    9ffec1
the diaphragm at full aperture to give fullfocusing screenbrilliance. The meter must
be "programmed" with the actual full aperture, and the diaphragm ring setting.
Grain.  Minute metallic silver deposit, forming in quantity the photographic
image.The individual grain is never visible,even in an eniargement,bui the random
nature of their distribution in the emulsion causesoverlapping,or clumping, which
can lead to graininessin the final image.
Graininess.   Visible evidence of the granular structure of a photographic
reproduction. Influenced by exposure, development, contrast charaiteristics and
surface of printing paper, emulsion structure and degree of enlargement. Basically
increaseswith increasingfilm speed.
Grey  card.  Tone used as representative of mid-tone of average subject. The
standard grey card reflects l8 per cent of the light falling on it.
Guide  number.  Figure allocatedto a light source,usuallyflash,representingthe
product of aperture number and light-to-subject distance required for  correct
exposure.
Hatation.  The production of "halos" round bright spots in an image, by light
reflecting from the back of the film-base. General film bases are given a light-
absorbingcoat-the anti-halationback-to  prevent this.
Highlight.  Small, very bright part of image or object. Highlights should generally
be pure white, although the term is sometimes used to describe the lightest tones
of a picture, which, in that case.may need to contain some detair.
lmage. Two-dimensional reproduction of a subject formed by a lens. When formed
on a surface, i.e. a ground-glass screen, it  is ar real image; if in space. i.e. when
the screen is removed, it is an aerial image. The image seen through a telescope,
optical viewfinder. etc. cannot be focused on a surface without the aid of another
optical system and is a virtual image.
Incident   light.  Light falling on a surfaceas opposed to the light rellected by it.

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Infinity.   Infinite distance.In practice,a distanceso great that arnyobject at that
distancewill be reproduced sharply if the lens is set at its infinity position, i.e. one
focal length from the film.
Interchangeable   lens. Lens designedto be readily attachedto and detached
from a camera.
Inverted  telephoto   lens. Lens constructedso that the back focus(distancefrom
rear of lens to film) is greater than the focal length of the lens. This construction
allows room for mirror movement when short focuslensesare fitted to SLR cameras.
lris.  Strictly. iris diaphragm. Device consisting of thin overlapping metal leaves
pivotin_eoutwards to form a circular opening of variable size to control  li-sht
transmissionthrough a lens'
Leader.  Part of film attached to camera take-up spool. 35 mm film usually has a
leader of the shape originally designedfor bottom-loading Leica cameras.although
most camerassimply need a short taper.
Lighting   ratio.  The ratio of the brightnessof light falling on the subject from
the main (key) light and other  (fill) lights. A  ratio of about 3: I  is normal  for
colour photography, greater ratios may be used for effect in black-and-white work.
Limiting  aperture.  The actual sizeof the apertureformed by the iris diaphragm
 at any setting. Determines.but usually differs from. the effectiveaperture.
Long-focus.  Lens of relativelylong focal length designedto provide a narrower
 angle of view than the normal or standard lens, which generally has an_angle of
 vie-w.expressedon the diagonal of the film format, of about 45 deg. The long
 focus lens thus takes in lessof the view in front of it but on an enlarged scale.
 Magicube.  Specialform of flashcubewhich is fired by mechanical(not electrical)
 meuns.Can be used only on camerasfitted with the appropriate socket.
 Manual   iris.  Diaphragm controlled directly by a calibrated ring on the lens
 barrel.
 Microprism.   Minute glass or plastic structureof multiple prisms sel.in a view-
 finder screen to act as ,i focusing aid. Breaks up an out-of-focus subject into a
 shimmer but images a focused subject clearly. Will not work satisfactorily at lens
 aperturessmallerthan /5'6.
 Mirror   lens. Lens in which some(usuallytwo)of the elementsare curved mirrors.
 This construction produces comparatively lightweight short fat long focus lenses.
 They cannot be fitted with a normal diaphragm.
 Modelling.   Representationby tighting of the three-dimensionalnature of an
 original in a two-dimensional reproduction.
 Neutral  density    f itter. Grey filter that absorbslight of all colours equally and
 thus has no effect on colour rendering with colour film or tonal values with black
 and white film. Primarily used with mirror lensesor to enable large apertures to
 be used in bright light conditions.
 parallax.  Apparent change in position of an object due to changed_viewpoint.
  In a camera *ith  separatJ viewfinder. the taking lens and the viewfinder view
                                                                              lr7

an object from slightly different positions. At close range.the image produced on the
 film  is significantly dilTerent from  that seen in  the viewfinder. Completely
eliminatedin single-lensrellex cameras.

Perspective.   Size. position and distance relationship between objects. Varies
according to viewpoint so that objects at different distances from the observer,
appearto be closer together with increasingdistance.Thus. a long-focuslens used
at long range and  it wide-angle lens used very close up provide images very
differentfrom that of the standurd lens used at a normitl working dist:rnce.

Photolamp  (34OOK). Photographiclamp giving more light than a normal lamp
of thc same wattage.at the expenseof filament life. Often referredto by the trade
mark Photollood. Arc usedwith type A colour films.

Plane. Level surface.Used in photography chielly in respectto focal plane, an
imaginary level surfaceperpendicularto the lens axis in which the lens is intended
to form an image. When the camera is loaded the focal plane is occupied by the
film surface.

Polarized  light.  Light waves vibrating in one plane only as opposed to the
multi-directional vibrations of nornral rays. Natural eflect produced by some
rellectingsurfaces.suchasglass,water.polishedwood. etc..but can also be simulated
by placing a special scrcen in front of the light source. The transmission of
polarized light  is rcstricted by using a screen at an angle to  the plane of
polarization.

Preset  iris. Diitphragmwith two settingrings or one ring that can be moved to
two positions.One is click-stopped.but does not aflect the iris. the other moves
freelyand alters the aperture.The required aperture is preseton the first ring. and
the iris closeddown with the secondjust beforeexposure.

Rangefinder.  Instrument lor measuringdistancesfrom a given point. usually
basedon slightly separatedviews of the sceneprovided by mirrors or prisms. May
be built into non-reflex cameras. Single-lens reflexes may have prismatic range-
findcrs built into thcir focusing screens.

Ref ill. Length of film usually for loading into 35 mm cassettesin total darkness.
Daylight refills are not now generallyavailable.

Relative  aperture.  Numerical expressionof effectiveaperture. also known us
/-number. Obtained by dividing focal length by diameter of effectiveaperture.
Resolution.   Ability of film. lens or both in conjunction to reproducefine detail.
Commonly measuredin lines per millimetre as ascertainedby photographing.or
focusingthe lens on. a speciallyconstructedtest target. The resolution of modern
lensesand films is so high that dill'erenceshave no bearing on normal photography
exceptwith the simplestlensesand lastestfilms.

 Safelight.   Light source consisting of housing. lamp and screen of a colour
 that will not affectthe photographic material in use.Safelightscreensare available
 in various colours and sizesfor specificapplications.

 Scale. Focusing method consistingof set of marks to indicate distancesat rvhich
 a lens is focused.May be engravedaround the lens barrel, on the focusingcontrol
 or on the camerabodv.

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         Screen.  In a camera, the surface upon which the lens projects an image for
         viewfinding and. usually. focusing purposes.In SLR cameras.almost universally a
          fresnel screen with a fine-ground surface. Often incorporates a microprism  orIi,       split-imagerangefinder.
         Selenium.   Light-sensitive substancewhich. when used in a barrier-layer con-
          struction, generateselectrical current when exposed to  light' Used in exposure
         meters.Needs no external power supply.
          Self-timer.  Mechanism delaying the opening of the shutter for some seconds
           after the releasehas been operated.Also known as delayed action.
lx      Semi-automatic     iris. Diaphragm mechanismwhich closesdown to the takingt        aperture when the shutter is released.but must be manually re-opened to  full
t "        aperture.
           Sensitivity.   Expressionof the nature of a photographic emulsion's responseto
            light. Can be conierned with degree of sensitivity as expressedby film speed or
         responseto light of various colours (spectralsensitivity)
         Sharpness.   Clarity of the photographic image in terms of focus and contrast.
         Largeiy sub.jectivebut can be measured to some extent by assessingadjacency
          emeJts.i.".the abruptnessof the changein density betweenadjoining areasof different
L         tone value.
                                                                              to provide a widerqIIL        Short-focus.   Lens of relatively short focal length designed
         angle of view than the normal or standard lens. which generally_has an .angle of
          vie"w,expressedon the diagonal of the film format, of about 45 de,e.The short
          focus lens takes in more of the view in front of it but on a smaller scale'
         Shutter   priority.  Automatic exposuresystemsin which the shutter speedis set
         by the photographer, and the cam-eraselectsthe lens aperture appropriate to the
            fiim spied und th. light reflectedfrom the subject. Such systems must meter the
            light at full aperture and use speciallyconnectedlenses.
           Silicon.  Light-sensitivesubstancewhich generatesa minute current when exposed
           to  light. Requires no external power source, but, in exposure meters. uses an
          externally powered amPlifier.t
          Split-image.   Form of rangefinder image"bisectedso that the two halves of the
         image are aligned only when the correct object distance is set on the instrument or.
            in  tle  .u..  of a coupled rangefinder. when the lens is correctly focused. SLR
         cameras may have a prismatiC split-image system in their viewing screen.Works
         on the rurn. principle as a microprism. and is restricted to apertures of  | 5'6 or
           greater.
            Stabilizer.   Alternative to  fixer where permanence is not required. Used in
          automatic processingmachinesand can now provide prints that will not deteriorate
           noticeably over many months if kept away from strong light.
         Stop-down   metering.  TTL metering in which the light is measured at the
           picture-taking aperture. As the meter just measuresthe light passing through the
           iens, there is no need for any lens-camerainterconnections.

                                                                                                                                                                            l 1 9

Studic  lamps  (32OoK). Tungstenortungstenhalogenlamps designedfor studio
 use. Have a longer life than photolamps, but a lowei specific outp"ut and colour
 temperature.Are used with type B films.

 Supplementary    lens. Generallya simplepositive(converging)lens usedin front
  of the camera lens to enable it to focus at close range. fh-e etrect is to provide
 a lens of shorter focal length without  altering the- lens-film separation, thus
 giving the extra extensionrequired fior close focusing.

 Synchronisation.   Concertedaction of shutter opening and closing of electrical
 contacts to fire a flashbulb or electronic flash at the correct moment to make
 most efficient use of the light output. Roughly speaking, FP or M-synchronisation
 is constructed to  fi.re-flashbulbs just before the shuiter is fully op.n, allowing
 a-build-up time, and X-synchronisition fires electronic flash exactiy at ttre moment
 the shutteris fully open.

 T.elephoto. Specialform of long-focus lens construction in which the back focus
 (distancefrom rear of lens to film) is much lessthan the focal lensth of the lens.
 Through-the-lens (TTL). Type of exposuremeterbuilt into the camera body
 and readingthroughthe cameralens.May measureeitherat full aperture or at picturetakingaperture.

 Type  A' Colour film balanced for use with photoramps (3a00K).
 Type  B. colour film balancedfor use with studio ramps(3200K).
 Ultra-wide  angle  lens. Extra-wide angle lens. usually those with an angle of
 view greater than 90p. For 35 mm camerasthe description usually appliesto lenses
 of shorter focal length than about 24 mm.
 Variable  focus  lens. Lens of which the focal length can be continuouslyvaried
betweenset limits. The lens must be refocusedwith each change in focal tengttr.
 Viewfinder.   Device or system indicating the field of view encompassedby the
camera lens. The term is sometimes used as a description of the type of
that does not use reflex or "straight-through" viewing systems and therefore"un1.ruhas
to have a separateviewfinder.

Vignetting.   Underexposure of image corners produced deliberately by shading
or unintentionallyby inappropriate equipment, such as unsuitable lens hood or
badly designed lens. A common fault-of wide-angle lenses,owing to reflection,
cut-off, etc. of some of                         very oblique rays. trrtay be caused in some long-focus                        .thelensesby the length of the lens barrel.-

Wide-angle.  Lens designed to provide a wider angle of view than the normal
or standard lens' Generally has an angle of view, expiessedon the diagonal of the
film format, of about 60 deg. o. mot.. The wide-ungt. lens thus takes in more of
the view in front of it but on a reduced scale.
Zoom  lens. Lens of which the focal length can be continuously varied within
statedlirnits while maintainingthe focus originally set.

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