Agfa Karat Reference guide

WHAT TO EXPECT T|ROM THE KARAT
The manufacture of cameras follows trends and fashlons-
f ust as does any other merchandlse. At the beglnnlng of such
trends, there ls usually some new idea on whlch a novel
design ls based-that, in lts turn, inevltably leads to some
change In the general appearance of the product. Once thls
appearance attracts attention and becomes popular,  lt
usually gets copled. The copyist hardly ever coples quallty.
He often overlooks or even Intentionally dlscards the baslc
ldea altogether and freguently relles on attractlng customers
by lowei prlces. So craftsmanshlp becomes replaced by
mass produdlon. Whether at thls stage the makers of that
partlcular product are stlll engaged In honest buslness or
lust In a racket malnly depends on what value they ofier
for money.
  The lists prlces of the varlous Karat models are between
14 4s. and L9 9s., and undoubtedly they are excellent
value-lndeed, more than one would expect-for that
money. The hlgh-class mlnlature cameras whlch mark the
 beglnnlng of the trend cost anything up to f60 pre-war llst
prlce. So lt ls obvious that there must be dlfferences
between them and the Karats.
  The Karats are very well made but, of course, not pre-
 clslon made In the watch-maker's sense of that word. They
are not accompanled by a wlde range of accessories and
 Interchangeable lenses. Thus they can nelther be expected
to answer to the same standards nor to be as versatlle as a
 Lelco, a Contox or an Ektro. Still, their photographic per-
formance  ls truly remarkable.
  The Karat "6.3" ls almost as easy to handle as a box
 camera, but lt ls about four tlmes as fasti the Karat "4.5"
goes further than any roll-film camera of the same prlce;
 whlle the Karat "3.5" wlll do work slmllar to the pre-
 clslon mlnlature as long as a standard lens is employed
 ln the latter.
  The last restrictlon malnly arlses because, as wlll be
 expected, the Karat lens ls not Interchangeable. Another

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 , baslc deviation from most other 35 mm. models is that the
 Karat takes only twelve exposures in one load Instead of
 the habitual thirty-six of ids forerunners. Many peopte,
 however, will argde that this is an advantage for imateurs,
 who do not wish to take such a large numbei of photographs
 in one run and are impatient to see thelr results prolessed
 and printed as soon as possible.
  Whether thls be true or not, the Karat ls an excellent
 llttle camera for the snapshotter who is discriminatlng
 enough to appreciate what such a camera will do for hlm-,
 and ls willing to find out how lt will do lt for him best. Just
 that ls described on the pages that follow.
Karat Cameras
The Karat is a mlniature camera, taklng negatlves lf In. x
 I In. (24 x 36 mm.)
  As negative material, the 35 mm. standard cln6-film  ls
employed for twelve exposures on a slngle load of film, In a
special Karat cartridge.
  The camera ls for daylight loadlng and unloadlng. The
Klpt-bgdy ls of light metal covereii wlth a very iiurable
ribbed plastic material.
  The dimensions of the camera are 4$ In. x2| In. x lf In.
 (l 1.8 x 7 x 4.6 cm.); lts welght about 15 oz. (420 grims)
complete with lens and shutter.
  The camera lens and shutter are fixed to a front panel,
which in turn is connected to the camera back by meins of
short square bellows and collapsible struts. The front panel
can be collapsed Into the camera body when not ln use.
 An optical dlrect vislon view-finder ls built on to the
long slde of the camera body.
 A built-in film counter automatlcally reglsters the number
of exposures taken.
  The film transport is coupled to the shutter so that rhe
latter can only be released when the film has been wound,
which serves a double purpose; two exposures cannot be
made on one film, nor can the film be wound on wlthout
having exposed lt.  Furthermore, the shutter cannot be

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released so tong as the camera fs not In lts ProPer "taklng"
posltion.'  There are three models of the Karat on the market:-
  KARAT "6.3'  ' is fitted with an f 6.3 lens In a three-speed
                                                                  Ball;shutter giving | 125, l/50,  li 100 sec. as well as "8" (:
short time) exposures.
  KARAT'tt4.itt  is fitted with an f4.5 lens in a four-spee{
shutter giving 1125, U50, l/100, lll25 sec. as well as "8"
exPosures
                                                              Rapl-d  icnnnf "3.5" ls fitted with a f3.5 lens In Compurshutter, giving speeds of l, | 12, | 15, 1710, | 25, Ul00'  | 1250,
l/500 sec. and "8" exposures.
   In addition, all modlls have a mechanlcal locklng devlce
on the camera body for making long tlme exposures "T"
(a' OTHERfew veryKenAfearlyMODELS-Inmodels of thel94lKarata Karatexcepted).ll iamc bn the merkct
ln very small quantities, incorporating a range'finder of the. split lmagr
type ioupled to the camera iens anii in one eyepiece with thc vlcw'
firiaer. The lens fitted ls a Korot-Xenor  f 2.8.   Finatty, there are two examples- knoin of a Karat lll "Luclmcter"
which incorporates, besides the features of the Karet ll, a bullt'ln
photo-electric exposure meter coupled to both aPerture and shutter'
ind olaced arounil the lens. Eithei the shuttcr speed to be used can
be pre-set and the corresponding aperture deteimln"9 Py mcans of
the'built-in meter or the ipertuie may be Prs's€t and tho sxPosurs
time determined by means of the built-ln meter.
  Both Karat tl aid lll follow closely the constructlon and general
handlinc of the Karat I as detailed in the following Pag.s. As, howcver,onli   iery small number of these modeb are ii ihE hands of photo-grailhers."   no further reference to thrir spccial featurss has beon madr
ln this Gulde.
Karat Lenses
Atf Karat modets are fitted with onosttgmot lenses, whlch
are free from optlcal defects and produce a clear, sharp
lmage over the entlre negatlve field.
  TF{E KARAT "6.3" ls fitted with a three-comPonent
                                                     (5 cm.) focalanastigmat lens, the lgestor f 6.3 with 2In.
length.
  fHg rcnnAT "4.5" has an Oppor anastlgmai f4.5 of 2f ln.
(5.5 cm.) focal length that consists of two slngle lenses and
6ne cemented paii, four lenses in all.

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  THE KARAT "3.5" is fitted with the Solineor (or Solinor)
f3.5 of 2 in..(5.cm.) focal length, similar ro rhebpp.r.  li
Sive: particularly.good definitlon, allowing one to inlarge
small sectlons of the negative to a considerlble degree.
   Af l Karat lenses covei an ansle of approximatetV 17" and
allow one to focus down to i ft. The Karar 6.'3 can be
stopped down to f 22, while the Karats ..4.5', and ,.3.5"
stop down to f 32.
  The treatment and care of the lens ls a matter of lmport-
ance. On account of lts chemical composltlon,-influence-soptlcal'glasr
of the highest quality ls susceptlble'to the            of
molsture, and for this reason tbuchins the slass with the
fingers should be avoided. The teni surfale shoutd be
cleaned occaslonally with a clean, soft chamois leather.

HAIIDTING TTIE KARAT
   To start wlth, we take it for granted that we have a loaded
    Karat cartridge and the camera at hand. Our first task is
    to load the camera with film. This should be done in subdued
     doylight.
   Loading the Karat
                 l. Open camera back.
           2. Raise the metal film guides.
           3. Place empty Karat cartridge in right-
               hand chamber.
           4. Place loaded Karat cartridge in left-hand
                chamber.
               5.  Pull out just sufflcient film to cover teeth
                of sprocket.
                6, Lower the metal film guides.
                7. Close camera back.
                8. Open camera front.
                9. Turn picture counter disc until letter
            "A" is opposite the indicator.
                10. Turn fllm winding knob as far as it will go.
                        I l. Release shutter.
              12. Turn film winding'knob once more.
        l.  Grett core should be token thot the loading is done in the dorkest
         ovoiloble spot, if outdoors, in the shodow of one's own body. To open the
         came.ra back, push locking button on the side wall 6f the Sody in
        the direction of the engraved arrow; this releases the camera bick,
        which can now be swung open on its hinges. Should the lock prove
            h.ard. tq 9pel, press the camera back agiinst the body lightly, and        the locking button will then move easily.
           R-aise the two film guides (which are above and below the longer
         side of the film aperture and partly coyer the sprockets of the film
         transport mechanism) so that they stand up.
       3. The empty cartridge which has to receive ihe exposed part of the
         film is placed in the chamber beside the hinge on which ihe camera
         back swings, so that the slit of the cartridge-faces the rails on which
        the film slides, the sign "Agfa" impressed in the cartridge being
      {'  ForuPPermost._greoter sofety the loaded Korot carfiidge should remain wropped,10     right up to the moment of looding into the comero. The loaded

cartrldgc ls pfaccd ln the left-hand slde chambcr, slmllarly to thG
       Gmpty one (see 3); again the sign "Agfa" to bc uppermost and
       the back of the film (glossy side) polnting towards thc cmpty
       chamber.
       l.  Holding the loaded cartridgc In position with thc thumb of thc
         left hand, sufficient film should be pulled out gently until the
       extreme end is within l/l0in. (2 mm.) of the slit of the empty
        cartridge. The teeth of the sprocket, wheel must .entage in thc
         perforation holes of the film.
    6. While making sure that the perforation of the film ls engaged ln
       the sprocket wheels, the two film guides (which had previously
       been raised, see 2) are now lowered into their original position to
        hold the film against the sprockets.
    7. The camera back is closed simply by gently presslng the hinged
       back against the main body, when the locking button will snap
        back to hold it securely fastened and light-tlght. Should the lock
       Rot snaP, force should not be used, but make sure that thc
         cartridges are properly pushed into position and the film guides
       have been correctly placed.
      t.  Press camera-opening button on top of camera body, when the
         lens board will automatically spring forward and come into working
        posltion.  lf the camera has not been used for some time it may
       happen that the lens board does not spring forward completely;
         in this case pull it out until lt snaps under the lock.
    9. Press the tii  of the index finger against the mllled centre ring of
        the film-codnting disc on top of the camera and turn the finger
        which, in thls position, engages the disc until the lettcr "A"  i3
        opposlte the Indication mark on the outer rim of the counter.
    10. Bi turning the film winding knob in the direction of the engraved
       arrow as far as lt will go, the first frame of film, whlch has been
        exposed to light by the lnsertlon into the camera, is wound into
        th6 empty cartrldge. /14oke sure that the shutter releose is not pressed
        by occldent while the film is being wound on, os the interlocklng device
        between shutter ond winding knob would be put out of oction.
         I l. To releasc the shutter, the body release on top of the camera  is
        pressed down. tmportant: With the Karat model whlch har e
      Compur shutter (sce p. l5 No. 3), this can only be done after set-
         ting the setting-lever of the shutter first.
    12" By lurning the film winding knob once more the first frame of
        unexposed fllm ls pulled out of the cartridge in front of thc film
         gate and the camera  is ready for the first exposure The film count-
         Ing dlsc wlll automatlcally polnt to numbcr l.


                                                                                                                                                                               r   Holding the Karat
        It ls obvlous that the camera should be held as steadlly as
    possible, as the slightest shake, even lf not seen in the
12 orlglnal negative, wlll become vlslble In the enlargement.

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                               HOLDING THE KARAT
                                                       (p. l2)

                                       FOR HORIZONTAL PHOTO.
                                          GRAPHS: Rest camera agalnst
                                              nose, while the eye looks
                                            through finder; keiep both
                                                 elbows close to the body, the
                                                                        left hand grasping the left part
                                                 of the camera. with the left
                                    thumb against the camer.
                                                     back, the right hand holding
                                                   the right of the camera, right
                                         thumb against camera back;
                                                 the right index finger should
                                                      reach over the camera top to
                                                   the body release.
                                     To climinate unwanted fore-
                                           ground in horizontal photo-
                                                     graphs the Karat may bc held
                                                       upride down.



 t     FOR VERTICAL PHOTO.
        GRAPHS: Rest camera against{I         forehead and nose, the left
         hand grasping the top of the
        camera with the left thumb
           agalnst the camera back, while
         the lowcr part of the camera
           rssts in the palm of the rlght
        hand with the right thumb
          against the body release.

       The Karat should be held as
          steady as possible, for even the
          slightest shake will become
          visible In the enlargement.
        Use the faster rpecdi wherc
           Practicablo.

A partlcularly steady hold of the Karat ls requlred when
    working wlth speeds below l/100 sec. Always stand with
    your legs apart.
    FOR HORIZONTAL PHOTOGRAPHS: Rest the Karat
    horizontally against the nose while the eye looks through
    the finder. Keep both elbows close to the body, the left-
    hand grasping the left part of the camera body with the
      left thumb against the camera back, the rlght hand holding
    the right part, again rlght thumb against camera back and
    the right index finger reaching over the camera top to the
   body release In readlness for exposlng the plcture.
     FOR VERTICAL PHOTOGRAPHS:  Rest camera vertlcally
    (upright) agalnst forehead and nose, the left hand grasplng
    the top of the camera with the left thumb against the cameri
    back, while the lower part of the camera rests in the palm
    of the rlght hand with the right thumb agalnst the body
    release In readiness for exposing the plcture. To release
    use finger pressure only, keep the hand and lts grlp on the
   camera steady.
     The actual presslng down wlll have to be done slowly and
   smoothly. The slower the exposure time, the smoother
   must be the release. For slow exposures In the hand lt ls
    advlsable to rest the elbows or at least to lean the body
    agalnst some support In order to avoid shake. Wlth the
    Karat which ls fitted wlth a Compur shutter, l/5 sec. and
   even l/2 sec. may In thls way be exposed without notlceable
   camera shake.
    A tripod is necessary when taking time exposures and lt
     ls also preferable for speeds from l/10 to I sec. A rigld
   tripod wlth ball-and-socket head should be employed to
    allow of changing the Karat from a horizontal to a vertlcal
    position. The tripod or ball-and-socket head top screw has
   to be screwed Into the tripod bush in the bottom plate of
   the Karat.
   Carrying the Karat
     However elegant lt may be to carry the Karat on a long
1{ strap hanglng from the shoulder, thls position is quite un-

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 sultable for qulck action. Many a good shot has been lost In
 this way. A better method is to carry the Karat on a short
 strap round.the neck, so that it lies on one's chest. Opening
the case and llfting the camera up to the eye is then a matter
 of a spllt second.
  There are a number of different types of cases for the Karat avairabre.
The.Ever-reody c3se carries the cam6ra ready for use; it.has a camera
 holding         :cre_w which prevents the Karat frorir falling out of the opened case. A leother purse ivith Zip fastener may be used-when the caniera is
 carried in the pocket or hand-bag.
Shooting with the Karat
      l. Open camera front.
    2. Make sure that the fllm has been wound on.
    3. Set shutter speed.
     !. Set stop.    5. Set distance.
    5. Determine picture in viewflnder.
    7. Release.
    8. Wind film transport knob.
    9. Close camera.
  . The manipulations here described should be practlsed so
that In time they will become practlcally automatlc.
 l. See p. 12, No. 8.
2.  lf the pro_cedure described for loading the Karat has been foilowed
    (see p. 12, No. 12) the first film is ready for exposure. To make
   sure that a new, unexposed film frame ii ready,'particularly when
     a- number of exposures have already been maie'on the film, one
   should try to wind on the film wind'ing knob-if it refuses to turn
    this is an indication that the film has Leen wound, otherwise one  '  has to wind the knob as far as it will go in the direction of the arrow
   engraved on the wheel.
        shutter speed on the Korot "6.3" ond Korot "4.5"  is set by turning3. {he   the index lever on the camera front opposite the shuttlr speei
   markings t-o the speed required. The figures 25, 50 etc., indicatc
   fractions of a second, e.g.  | 725 sec.,  I /50 sec. etc.
   _.Ihe Shutter of the KorZt "3.5" is the Compur or Compur Rapii. . There are two actions involved when setting dhis shutter:'(o) setting
   the shutter to the exposure time required, (b) setting trie'shuttei
   t{'nsioning lever (cocking the shuttei). The-shutter ipeeds of the
  Compur are: l, l12, ,15, l/10, ll2S, llS0, l/100, l/30Ottr second.
   Those of the Compur Rapid : l, | 12, I lS, l'l 10, I lZS,,/5b,  | / lOO,  | /250 15

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                i
 l: Open the camera front by pressing the camera-opening button on top of
the camera body. 2: Make sure that the film has been wound on by tryini to
wind film-wlnding knob. 3: Set shutter speed (see p. 15, No.3).  i: Sbt itop
 (!ee p. 16, No. 4). 5: Set distance by turning the front cell of the lens to tha
distance mark. 6: Determine picture in the vicwfinder. 7: Release by sently
 pressing the body release lever. 8: Wind film transport knob. 9: Closi dmeri
by pressing locking levsr and pushing lens board backward rimultaneously.
                 UNLOADING (p. 18)

 l: Make two blind aX-
posures by winding and
releasing twice. 2: Open
camera back by pushing
button on side wall in the
direction of the arrow.
3: Remove receiving car-
tridge with the exposed
film. 4: Close camera back;
or load again as described
on page 10.
|(A-t

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Unloading the Karat
        havlng taken all the twelve exposures (the number  -Afterol exposures ls automatically counted on the film counter),
the film can be removed in iubdued doylight.
      l. Make two ..blind" exposures.
    2. Open camera back.
    3. Remove receiving cartridge.
    4. Close camera baik, or loa-d camera again.
 l. To make the two blind exposures the film winding knob is wound
   on and released twice, when the film counting disc viill show to "A".
1 9.pun back.as described on p. l0 (No. l).3. The cartridge nearest to th'e hinge of th'e camera back which now
    contains the exposed film is removed; a short tongue of film will
    projecl from the slot of the cassette. rhis tongue-must neither be
    pushed completely into the cortidge nor pulled outl As soon as it has
   been removed th.e cartridge should be                                        -wrapped up, preferably in                  until the film-is taken out for iiocessing'in the dirk-    ffi.n"n"t,
{.  close cameraas described on p. l2 (No.7) or reroad, see procedu16   on p. 10.





                                                   19

ITARAT CARTRIDGE +ND FITIUS
  The Karat film ls the standard cln6 film of 35 mm. wldth
                               is identical with th,e materlal used In   .nJ ir l.ifoiated.  lt   the majority of other 35 mm. cameras, e.g.,Leico, Contox,                                                            suitable    etc., wiih th'e notabte difference that it is of i length
                                                                      as   for twelve exposures as compared with 36 exPosures   used in the other models. lt is obtainable as:-
                                                        slmplest    KARAT CARTRIDGE WITH FILM. lt is the
   solution of the Karat film packing. The re-ady-cut film for
   twelve exPosures with a sukable allowance for the necessary   ;;bllnd"           ixposures ls supplied In a special Karat cartridge
   which can bb loaded ln day'ight Into the camera (see P.23).
                                                                           as    uNSPOOLED 35 MM. FILM. This ls supplied either
   5 ft-. lengih (:  36 exposures) or as bulk film in lengths fioT
    l8 to 20b ft.' In either case a suitable length has to be cut otf
   .na loaa.d into the Karat cartridge in the darkroom (see
   P. 22\.

   Safelight
                                                          be    The loadlng of cartridges with unspooled film has to
    carried out in the darkroom.
       In the case of panchromatlc films (see p.23) only the.dark
                                                       always   green "panchro" safelight. m.ay be g1e.d'. bu1. it ls
    safer to work in compleie darkhess. This is not difticult. lt
     is, however, advisablL to practise  filling- with a dummy film
    niti in daylight before-.stirting the daikroom work'
       lf orrhochromatic films G.-" P. 23) are used the red
   "ortho" safellght may be used.
       In the ..ru oT positive film (see p.241- amber light wlll do.
'  Handling, Cutting and Winding the Film
    When handling the actual film, particular care must be
   taken not to touEh lts emulsion (mitt) side. lt should only
   be-handled and pushed into the cartridge by holdlnt th9
20 fiim on either siie of its edge, preferabf between thumb

.i

and index finger. At the same time, lt is of no less lmportance                                        il,t
that the spot on which the loading is done should be per-
fe91ly dry,-clean and dust free. Only-a clean, spotless negatlve
will produce the deslred result.
 To measure the required length of film for the Karat
cartridge             the unipooled or- butk                                          the edge of          from.                                          -length,the work-bench can be-marked with a'notlch or a dra:wing
pin to Indicate the distance.
  Tlre.-length of film^ requlred to load'a Karat cartrldge
wlth 12 exposures is 24 In. (60 cm.). lt is possible-but n6t
very advisable-to get more film (up to  lil exposures) into
one cartridge-the film length required thdn wouid be
33 ln. (84 cm.).
^ ,To pr.epare the film to be loaded into the Karat cartrldge,241n. (12 exposures plus leader) are cur off from the dn-
spooled or bulk length in a straight cut across the film
 betwee.n two. perforation holes. It is importont thot the
 curved 9r w_elge shoped ends which are sometimes found on the
 unspooled 5 ft. lengths ore cut offi they connot be used in the
 Karot.
           f t is advlsable to cut a number of 24In. lengths of film for
the Karat cartrldge at the same tlme. Each film not im-
mediately loaded into the cartridge should be wound in a
rather sftall roll, emutslon slde (rilatt) inside, and a rubber
 ring placed over thls roll to prevent it from springing open.
All this prepared film should be carefully wrippet  i-n black
 pqper and pl_aced into a light-tight tin for storag-e. The maln
advantage of the "prepared" stock lies in the fact that the
 films which have been kept rolled for some time feed mone
 easily into the cartridge than the freshly cut ones.         ,
  When wlnding the film, great care must be taken that no
 pressure is put on it and that its ends are not squeezed when
drawing throu_g.h the hand ) nor must ony attdmpt be mode
 to tighten- the film when rolling it by pulliig the end. Fallure
to take lhes_g precautions may result in fogging and scratch-
                                            Eischarges to ing 9f the film and causing staric electricil spoll lt.                        /

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 .How'to Load the Karat Cartridge
   The Karat cartridge. is a one-pi9ie shell wrth a lrght-
  trapped slit and a gulding spring ihside. The caitiioge Ean-
  not be opened.andccinsequ'entli the fitm has to be fEd rnto tne cartridge through the slit.
       l. Work inappropriate safelight.e                                       '     2. Prepare fil;d.
     3. Push film into cartridge.
 2. The film is prepared as describe d on p. 22.
 3. The fitm is het<i uy itt'Lai"r i"ri, iii"'"na is pushed Into the stit of     the cartridge emuision (J mlt)'jide inside; the film is feA into'ifre
     cartridge by pushins  it iir gradu'ally, about t l".rr      tim-e, until oniy    the last indh projects out-of the Karat cartridge."Ji
 The Choice of Material
   There ls no su-ch thrng as-1:'best" film for any or every
 klnd of.prctlr.e. Each.tyi'e of film tr.s ciii.rn?,#{...rrsrrcs,
                regard          with                                 t'o colour sensittvtty,                                            - speed,'     gradation, :-tl,::?]l),racttude, and,           more                       particularly,                                   graln.                                                               .
  oRTHocHRoMATtSM AND pANcHRoMATrsM. The ordinary             ."s.ilve.r bromide', emulsion i" oniv' slnsitive to
 violet and blue light, and therefore bound to iive an unrrue
 black-and-white iendering when taking phoi&'i*f,, of sub-
 jects containing yellow, gl-reen and/orlio (.rir-Jcticallv  all
 oDrects do). An improvement has been made in the ortho-
cnromaflc emulsion which is sensitive also to yellow and
green, while the "panchromatic" film has been ,i,.a. ,"nii-
tive not only to viblet, blue, yeltow and green, ULt also toreo..              particularly fast panchromatic films are over-,     .50me
sensitive to red and will render this colour too light. T-he
advantages of having a negative r.t"ri"r rlniiiiu" to arlcotours-violet,                     lue, yellow, gneen and red_are so striking                           fthat it was evid.ent tr,.t ti'tE genuine panchromatic film
U?1tld,j,:tl3;eltre                  other fi.tm frpq for's".;;t ;urposes.                     n3t. containilg rgq (green tandstapis) or]^lj.,l,_r?ijl,lj_e1sy.nen rrthting conditions tend to bloi-out reds to6 much         portraits                taken                     In             .                            incandescent light),vchromatic!I?r of           materials                   are yery/                    useful.                                                                          ''  ortho- Zg

INFRA-RED FILM. Infra-red fifm is a ncgatlve materlal whlch, unllkc
    the orthochromatic and panchromatic  films, is made sensitive to infra-
    red rays, which are not iisible to the human eye. Special applications
    of this material: black-out photography, long-distance shots, mist
                              and research                                           work.                          copying                    scientific     penetration,'                                                        obiccts (books,                                         black-and-white                       Fdr iopying    ORDINARY              FILM.
     fedgers, etc.) a positive film oI3 to 10" Scheiner can be recommended.    Besides its qualities of fine grain and high brilliancy, it Possesses thc
     further advahtage that it can be handled in an amber darkroom  light.
    SPEED. The sensltivlty of film materials to llght In
    general is measured in Scheiner, Hurter and Driffield, Weston,
   D,n or G.E. degrees, Scientists and manufacturers agree
    that none of the metliods employed to determlne the sPeed
    of films is entirely satisfactory, and continue giving prefer-
   ence to one or the other of them. In any case, although
   speed ts a very obvious asset, lt is also a quallty whlch must
   be pald for by possible disadvantages of the materlal In
   some other reipect. To call the fastest film the best would
    be Just as foolish as to select a racing car for dally motorlnS.
      While a scientifically correct conversion of one speed rating system
    to another cannot be made owing to their different principles'.the
    following list gives some guidance as to their practical relationship.
          CONYERS'ON TABTE OF DIFFERENT SPEED DE6REES
    European A.S.A.    G.E.  Weston    Scheiner Index   Speed Speed H. & D.     Din
           ,2          0.8                          I           0.6      30      l/10          l5             t.5         2            1.2    62     4lao           l8           3           4           2.5     r2s    T lto          2l         6             7.5        5     250    10/10         24                         t5          l0     soo    13/10         27           a225,         30         20     1,000  16110          30         50          60        40     2,000  19/ l0          33        100           t20        80     4.000  22fi0

       Slow films of less than about 23'Scheiner can be usefully employed for
     scientific photography, copying and architectural details. Their main
     advantage-is in their extremely fine grain, making special development
    unnecesiary. Their disadvantages  are in their inability to coPe with livs
     rubjects in other than exceptionally favourable lighting conditions, lack
     of latitude and mostly hard gradation.
      Medium films of i4o-29" Scheiner are the right materlal for the
24 beginner, ind can be well employed for any of ihe averate subiects.

TIIE TECHNIQIIE OF FOCUS
 Depth of Focus
  The lens fs focused at some definlte dlstance. That means
 that lts posltion relatlve to the film ls adJusted in such a
 wa), that whatever ls exactly at the focused distance wlll be
 represented by a "sharp" lmage on the film. Everything
 else-everything nearer to the camera or farther from lt-
 will be, strlctly speaklng, "unsharp".
 _-ln practlce the decllne of definitign ls, of couise, lradual.
Thus there ls a zone-stretchlng from somewhere.ln front
 of the fiocused distance to soriewhere behlnd lt-whlch
 wlll oppear sufiiclently sharp to the human eye. Thls ls called
 depth offocus.
  Now, what should or should not be accepted as sufrlclently
sharp is debatable. Certain standards, however, have beeir
agreed upon. lt ls agreed that any pln-point represented on
a 35 mm. negative by a "dot", the diameter oi whlch does
 not exceed l/30th  ffiffi., should be regarded as sharp. The
technicaf term for that "dot" ls circle of confuston.
  The llmits defined by the clrcle of confusion are reached
more qulckly wlth one type of lens than wlth some others.
The results also vary wlth the condltlons under whlch one
definlte type of lens is used:
 . Short focus lenses yield more depth of focus thon long focus lenses.
  Small oPeftures yleld more depth of focus thon lorge
 opertures.
  For focuslng distonces yleld more depth of focus than neor ^
focuslng dlstonces.
Control of Depth of Focis
_ The depth of focus-dependent on the distance actually
focused at, the aperture employed and the focal lensth df
the lens-has to-be ascertainei from cixse to case.- The
Karat lens ls not lnterchangeable, so we do not need to
consider "focal length". There remalns the interplay of
"aperture" and "focusing dlstance". Their effect tai be 2g

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   read off on the depth of focus table on page 35. Let us
   assume we are working with f 5.6 and the lens is set to 8 ft.,
  we find in the horizontal column f5.6, above the bold    dist-ance figure 8, 6-1Of;, and below it9-$, and so the range
   of focus stretches from 6ft. lOf in. to 9ft. 6f in. WhEn
   working with the lens set at the same distahce of 8 ft.,
    bu! with ap_ertur_e f 3.5, the range of sharpness will extend
   onfy from 7ft.3[in. to 8ft. i-Of in.-while aperture f8    will produce a sharp area frop 6ft.6in. to iOft. 4*in.
 .  Note how we can vary the area of sharpness by playing with
   the stop and without changing the seiting of the'disiance:
   the smaller the stop the largei the depth bf focus.
     So the stop (aperture) is one of the variables by whlch a
   convenient zone of sharpness can be obtained. The other
   one is, of course, the diitance setting. Let us compare the
   depth values for, let us say, apertureJ5.6 at a distance first
    of  f 0ft., then of 70ft: and lastly of 40.ft. We tearn that in
 , the first case the depth of focui stretches from 8fu.4 in. to
    l2ft. 6[ in.; in the second case from l4ft.2* in. to 33 ft.
    9*in.; and in the last                        case from 2}ft. f in. t6 2lTft.4tn.   So we see confirmed that the depth of foius grows as we set
    the le ns at d istan ces farthe r and firthe r away fiom the came ra.
       Incidentally, we also conclude that the depth of focus in
    front of the focused distance is always mor'e limited than
    the depth gained behind it. With the lens set at l0 ft. we ger
   over I ft. depth in front of the focused distance and arm6st
                     we get over 5ft. in front of the    7*tt. behind it. At 20ft.    focused distan€e and l3{ ft. behind it. At 40 ft. we get 18 ft.
     in front and 177 ft. in tfie rear!
                                                             focus- In    - The c_om.parative shallowness of the depth of   front of the focused distance will sometimes make lt
    necessary-e.9. in landscape photography, where the sub-
    ject may have to include much foreground-to set the lens
    nearer than the main point of                                                      lies, in order to gain                                      -interest               sharpn-ess    additional                      towards                                the                                  foreground                                                while                                                     coveiing
    the main poinr                    of interest                           by                               the                                 depih of focus                                                            thE              {i                                                  behind
    focused distance. This trick, however, musr be used with                      I
30 moderation. lt shoqld be recalled that the widely held ldea

that everything is equally sharp wlthin the depth of focus
area and completely unshar.p outside these limits is quite
wrong. There is a gradual decline of sharpness even within
the depth of focus areas. Critical "pin-point" definition can
be expected only in the plane actually focused. So care
should be taken to place the focus as near as possible to the
spot on which the greatest sharpness is required. Thus in
the case of distant landscapes use should not be made of
 the hyperfocol distonce (described below)  if the sharpness  is
 required in the far distance; focusing at the far distance will
give better results.
  When a lens is focused on such a distance that the depth of focus
iust reaches the far distance (infinity) then the lens is focused on the
 "infinity-near- point" or hyperfocal distance. This adjustment of focus
 is advisable when it is desired to secure adequate sharpness from the
farthest distance to as far as.possible in the foreground, rather than
extreme sharpness in the far distance only (see Hyperfocal Distance
Table on page 32).


                                                                                                                                                                                                                                                                                         .Practical Focusing with the Karat
  The Karat photographer's aim should be to get a pictur'e
by seizing a situation as he comes across it without many
preliminaries, withoutatripod,and  in particular, without loss
of time. To attain this he will have to know his camera nor
only inside out, but he needs a ready-for-shooting setting
(: zon" focusing), that )rields a sharp picture every time.
Here the relatively short focal length of the Karat lens is a
great help as it offers the advantage of a comparatively ex-
tensive depth of focus even at wide aperture.
  From what was said about depth,of focus on the previous
pages, it is clear that the stop is used to regulate the
definition in our picture across the depth (both foreground
?nd background) of the point at which we have actually
focused. Now, the idea could occur to the beginner to try
to use the smallest stop every time just to make sure of
sharp pictures. That, however, would mean that in the
majority of cases he would not arrive at an instantaneous
exposure-because, while it is true that the smaller the stop
the greater the depth of focus, it is also true that the smallei
the stop the longer the exposure time, owing to the fact 31

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that by stopplng down the lens lts openlng to the ltght ls
obviously reduced.
 - In consequence, the besc zone fiocuslng is the compromlsebetween a well-selected medium stop with a sultable
distance setting, yieldlng a fairly deep zone of definitlon
but stlll leavlng one at liberty to use reasonably short
exPosure times.
  The Karat's "4.5" and "3.5" have marklngs for two zone-
focusing settlngs.
                                                                                                                                                                                     | , thc l. fAR setting: the stop is set to the rcd dot between  f 8 and f  |    lens is set to 30 ft., everythlng between 15 ft. ond infinity is shorp.
2. NEAR setting: the stop ii set-to the red dot between i8 and ill,   the lens is set to l0ft., everything between 8 ond 13ft. is shorp,
  The more frequently used zone focusing sertings are set
out in the zone focusing table (below) and it may be found
useful to coP), them out on a piece of paper whlch can be
fixed in the top flap of the Karat case for ready reference.

                   HYPERFOCAI D'STANCE
                                       Depth of focus
    Stop         Distance settlng       from        to
    3.5                50 ft.               29 ft.     @   1                  40 ft.               25 ft.     @    5.6                30 ft.                  17 ft,     @      I                    25 ft.                   l5 ft.     @          | |                           2ilfit.                   l2 ft.     @   16                    15 ft.                 8 ft.     @

                  ZONE FOCUS'NG
                                         Depth of focur
    Obiect       Distance settlng      Stop    from      to
Portralts                 3.5 ft.            3  ft.   4  ft.
Children         6  ft.       8     sft.       7.5ft.             tt                 ...         l0  Jt.      8       7.5ft.   15 ft.           {                                                                                                                                                       il
Groups          13 ft.                         9.5 ft.   2a ft.                         .I
                    25   ft.               I       lsft.    @                    20   ft.                fl          ll   ft.   @
                     For convcrslon Into mctrlc unitt scc p.5t.