Gossen Profi-flex User manual

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General introduction
This PROFl-flexattachmentconverts your PROFISIXexposure meter for operations
which are not feasiblewith an ordinary meter. Together with the PROFl-flexattach-
ment the extreme sensitivityof the PROFISIXis utilized fully. For each subject,
where exposure of very narrow and inaccessiblespots has to be measured,the
flexible PROFI-flexwith its small measuring aperture will be of great assistance.
The PROFI-flexis especiallysuitable for exposure measurementin macrography,
ground glass measurement,in microphotography,for  density measurement on
negativesor transparenciesand for luminous density measurement.Even contrast
measurements(densitycontrast,subject contrast etc.) can easily be assessed.
Note: Before reading the following detailed instructions,you should be completely
familiar with the general operating procedures outlined in the PROFISIXowner's
manual.




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Attaching to the meter
Remove the detachablefront shield covering the accessory iacks from your PROFI-
SlX. Slide the hemisphericaldiffuser (1) of your PROFISIXto the right. Align the
PROFI-flexattachmentwith the front of the meter so that the plugs on the attachment
are opposite the jacks in the meter and the recess in the attachment is opposite
the hemisphere.While holdingthe PROFI{lexby its ribbed sides,push the accessory
straight onto the meter. When attaching or removing the accessory, make sure to
pull or push  it straight out, otherwise the plugs or jacks may be damaged. When
attached to the meter, it automatically adjusts the meter sensitivity so that direct
readings can be taken without making ad,ustments.





Set  t h e  f i l m s p e e d a c c o r d i n g  t o   t h e   i n s t r u c t i o n s f o r use for the PROFISIXmeter.

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Care of your PROFI-flex
On ly the   f inest materials are used
in  your  PROFI-flex. However, the
f i b e r s  i n  t h e p r o b e c a n b e d a m a g e d
 if subjected to abuse. Breakage of
the  fibers  will cause  loss  of  effi-
ciency, affecting the  calibration of
t h e p r o b e . R e a s o n a b l e c a r e s h o u l d
b e e x e r c i s e d w h e n u s i n g t h e P R O F I -
f l e x . D o n o t s u b j e c t   i t  t o a b n o r m a l
stress, bend  it at very sharp angles,
o r  allow ob jects  to  strike o r  rest
o n   t h e p r o b e .
Technicalinformation
The PROFI-flex consists of approx-
imately 4,000 glass fibers of around
0 . 0 7 m i l l i m e t e r s d i a m e t e r e a c h .
L e n g t h          400 mm
M e a s u r i n g A p e r t u r e
                  5 m m d i a m e t e r
                  e q u a l t o a p p r o x i -
            m a t e l y 1 9 . 6 m m 2
Difference in sensitivity between the
attachment and the meter itself,
w h i c h  i s a u t o m a t i c a l l y c o r r e c t e d
                  3 sto ps
                  a t 1 8 D I N E V - 2      A n g l e s e n s i t i v i t y o f P R O F I - f l e x
                  L e .
                  a t 2 1 D I N E V - 1
M e a s u r i n g A n g l e a p p r o x . 3 0 o

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       Reflectedlight measurement  i
  .       The PROFI-flexis particularlysuitablefor macrophotography,for close measurement (            of small areas and for detail measurementsof small subjects which are usually
I I         inaccessiblewith an exposure meter, e. g. scaled down copies of  interiors or
I I                    ' landscapes,details of architecturalmodels, circuit designs, etc.I I         Direct the measuringaperture of the PROFI-flextowards your subject taking care  t           that you or the meter do not create a shadow. More reliable resultswill be obtained
          by using a grey-card.                                                                                               'the          For this purpose place a small mid-grey card in front of the important part of
          subject and direct the measuringapertureagainstthe grey-cardwithout shadowingit.
       When taking the measurementensure that only the area of the grey-card is read,                                                                                                                     *                  if the distance is too great the adjacent surroundingcould falsify the reading.
        You measure then in the usual way: Press the red measuring button (6) of the
         PROFISIX.After releasingthe button, the value measured at that moment will be
          stored automaticallyin the electronic memory of your PROFISIXfor one minute.
         Next turn the computer ring (24) until the indicator needle is preciselyat "0". Read
          the shutter speed and f/stop combinationssuitable for your subject on the scales
          1 7 a n d 1 8 .
                     " The distance between grey-card and measuring aperture must not be grealer than the diameter
                  of the largest circle which you could draw on the grey-card.





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Groundglass measurements
Exposure measurementin general
The PROF|-flexis ideal for ground glass measurements.All variationssuch as filter
factors, factors for bellow extensionand stray light are compensatedfor.
The measuring aperture of the PROFI-flexis put in contact with relevant area of
the ground glass. Externallight must be eliminatedby means of a black cloth' lt is
advisable not to measure at the corners of the ground glass as (particulary with
wide angle lenses) a decrease of light can be registered,which is essentiallya
feature of the lens. By using a fresnel lens this effect can be largely overcome.
To determine the exposure time  it is expedient to use a grey-card which should
be placed in such a way, that  it receives th6 same illuminationas the important
part of the picture to be measured.
You press down the red button (6), the meter gives a reading,the value measured
at that moment will be automaticallystored in the electronic memory of the meter,
when you releasethe button.You then rotatethe computerring (24) until the indicator
needle (4) points exactly at the "0" on the scale. On the scale (17) you now read
tne expdsuie time whiclr is opposite tl1 on the aperturescale (18).f/1 is your read-
ing index for this working aperture measurement.Extensionfactors due to bellows
or filters used are automaticallycompensatedfor.
The reading index f/1 is a value found to be practicallyuseful.On page 11, you will
find instructionson how to determinean individualreading index as best suited
for your requirements.

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Exposure measurementwith twin lens reflex cameras
The viewing lenses of twin lens reflex cameras are not provided with diaphragms.
The relative aperture of the viewing lens is usually the same as the maximum
aperture of the taking lens. Thus you can practicallyuse the reading index tor t/1
maximum aperture as described in 1. For a smaller working aperture the computer
ring (24) of the PROFISIXshould be used. Rotate the computer ring to set the
exposuretime which was indicatedoppositef/1 now oppositethe f/stop on scale (18)              Iwhich equals your viewing lens aperture.Then read exposure time and f/stop for
your taking lens on the scales (17) and (18).
Exposure measurementon reflex cameras with fully automatic diagrams
Set the required working aperture manuallyand then take the reading.
When measurernentnot possible with working aperture
This may occur with smaller apertures or where filters on the camera lens will
have to be considered.
How to solve this problem:
1. Use the white side of the grey-card,this yields 21l: stops which wi'll have to be
   deductedfrom the value measured.For that purpose,you set the white index line
   (15) on the scale (13) to -211t.
2. You measure with the lens wide open and compensatethe difference in stops
  down to the working aperture by extending the exposure time accordingly.



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            This is easily done by using the computer ring of the PROFISIX:you rotate the
             ring (24) until the exposure time indicated at the reading index f/1  is opposite
            the maximum aperture of the lens. Shutter speed and working aperture of the
            lens can be read on the scales (17) and (18).1,      3. You may also measure without filters and then correct for  filter factor sub-
            sequentlyor set the ring for correcting factors (23).I       Determination of individual reading Index
           1. By comparison measurements:
            Set up your camera to face a grey-cardand take a reading.Then null the meter
             with the computer ring (24) and determine the shutter speed correspondingto
            the aperture set on your camera. Next take a reading of the grey-card off the
          camera ground glass. Note the f/stop that appears opposite the exposure time
           determinedwhen reading the grey-card directly. This is your individual reading
            index.
           2. For calibration use an average scene for which the optimum shutter speeds
           and f/stops are known. Set that previouslydeterminedaperture on your camera,
            the shutter speed is known or tested again by taking a test photo. Next measure
           through the ground glass at the most importantpart of the subject and null the
             rneter again. Your reading index is the f/stop which appears opposite the ex-
           posure time previouslydetermined.
            For future referencemark that index on the PROFISIXwith one of the stickers
            supplied (see illustrationpage 12). II
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     Contrastmeasurement
         In additionto proper exposuremeasurementsthe contrast range or scene brightness
          is of great importance for quality results. The scale (2) of the PROFISIXallows
             reading in a contrast range up to 6 stops. For this type of works adjust the       Qgect
      PROFISIXfor extended measurement.
*       Subject contrast
       Measure brightestand darkest spot either direct at the subject (see page 7) or on
        the ground glass (see page B). The differenceof the scale values indicated is the
        subject contrast expressedin exposure stops.
        lllumination contrast
      Use a grey-cardfor measuringthe weaker general light and the effect light (see:
       "measuringthe illuminationintensity"page 17). The differencein readingsobtained
          in those two measurementsis the illuminationcontrast which you can modify in
       case of need by shifting the lamps.
      The admissiblecontrast depends on the job requirements,the film and the photo-
       graphic paper used. Please refer to manufacturers'recommendations.
      Our recommandations:
        Black and white negative film
       Dependingupon the photographicmaterialthe contrast may be 2 to max. 6 steps.
      When using a colour negative film from which paper prints are to be made, the
        contrast should not exceed more than 3 steps. lf the colour negativeis to be used
         for the productionof colour transparencies,the contrast may be somewhat higher.
       Using a colour reversalfilm, contrast of more than 6 steps should be avoided.

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Densitymeasurement
Density measurements can be taken of film negatives and transparencies using
the PiOFI-flex and a light box. For accurate readingsthe light box must be uniform
in intensity,or a uniform section of the box used for measuring purposes. To
measure the absolute density of an area of film, first take a reading of the light
box by itself. Record the scale value obtained as So. Next place the. area of the
film to be measuredover the very same spot on the light box and take a reading
with the PROFI-flex.Record the scale value as SN. The density of the film can be
calculatedfrom the formula:
                       D -  0.3 (So- SN)
Each change of one Exposure value equals a density change of 0.3. The r/r marks
on the scale are equivalentto a density change of 0'1
Example:
Scale readingwhen measuringwithout film:  So = 18rlr
When measuringwith film on the light box: SN = 152/r
D  :  0.3 (181/r- 15212)-  0.3x221t = 0.3x8/r =  0.8
The density of the area measured is 0.8.





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lF      Density range of the film is the difference in density between the lightest area and
        the darkest area. For determiningthe density contrast,first take a reading at the
         lightest area (scale value S,o*.) and the darkest area of the negative (scale value
        S ' nin . ).
      The contrast K can be calculatedfrom the formula:
                              K -  0.3 (Sror. -  S.in.)
       Dependingon the requirementsof the work in hand (enlargingof paper pictures,
       preparationsfor printings etc.) be sure to mind the instructionsfor the admissible                    I
 rr       densitv- contrast.Intrast.                                                                                                               "1 ]
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