Gossen Measuring Probe User manual

Contents                                               Page
General introduction                                                           1
Attaching                                                      3
Technical information                                         4
Reflected light measurement                                  5
Ground glass measurements                                  6
Exposure measurement in general                            6
Exposure measurement with twinlens reflex cameras         I
Exposure measurement on reflex cameras with
    fully automatic diagrams                                   9
When measurement is not possible with working aperture    I
Determination of individual reading index                   10
   with grey card                                           10
   with test photos                                          10
Contrast measurement                                       13
Subject contrast                                                13
lllumination contrast                                         13
Density measurement                                        13
Luminance measurement                                     14
Measurement of illumination intensity                       15

General introduction
This MEASURING PROBE attachment converts your system exposure meters LUNA-
SIX F, LUNASIX 3 or LUNALITE for operations which are not feasible with an
ordinary meter. Together with the MEASURING PROBE attachment the extreme
sensitivity of the system exposure meter is utilized fully. For each subject, where
exposure of very narrow and inaccessible spots has to be measured, the flexible
MEASURING PROBE with its small measuring aperture will be of great assistance.
The MEASURING PROBE is especially suitable for exposure measurement in
macrography, ground glass measurement, in microphotography, for density mea-
surement on negatives or transparencies and for luminous density measurement.
Even contrast measurement (density contrast, subject 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 manual of your
system exposure meter.

Attaching to thd system exposure meter

                                                Fitting the MEASURING PROBE is very easy:
                                                 Shift the diffusing sphere so that it fits into the
                                    key of the attachment, and engage meter and
                                 the attachment while pressing button. Aft,er
                                      depressing the button, the system exposure
                                  meter and MEASURING PROBE are firmly
                                          connected.
                                         Set the film speed according to the instructions
                                                for use for the system exposure meter.





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                               camera manuals, ou=butkus.org,
                                 email=mike@butkus.org, c=USButkus               Date: 2020.09.30 19:38:29 -04'00'

Technical information
Only the finest materials are used
in your MEASURING PROBE. How-
ever, the fibers in the probe can
be damaged  if subjected to abuse.
Breakage of the fibers will cause
loss of efficiency, affecting the ca-
libration of the probe. Reasonable
care should be exercised when
using the MEASURING PROBE. Do
not subject it to abnormal stress,
bend it at very sharp angles, or
allow objects to strike or rest on
the probe.
The MEASURING PROBE consists
of approximately 4,000 glass fibers
of around 0.07 millimeters diameter
each.
Length            400 mm
Measuring aperture
                 5 mm diameter
                   equal to approxi-
                  mately 19.6 mm2
Difference in exposure values be-
tween the attachment and the meter
 itself at 21 DIN/100 ASA                                    Angle sensitivity of MEASURING PROBE
                 +4LUNASIXF+2   LUNASIX3-3     LUNALITEMeasuring angle approx. 30o

Reflected light measurement
The MEASURING PROBE is  particularly suitable for macrophotography,  for
close measurement of small areas and for detail measurements of small subjects
which are usually inaccessible with an exposure meter, e. g. scaled down copies
of interiors or landscapes, details of architectural models, circuit designs, etc.
Direct the measuring aperture of the MEASURING PROBE towards your subject
taking care that you or the meter do not create a shadow. More reliable results will
be obtained by using a grey-card.
For this purpose place a small mid-grey card in front of the important part of the
subject and direct the measuring aperture against the grey-card without shadowing  it.
When taking the measurement ensure that only the area of the grey-card is read,
 if the distance is too great the adjacent surrounding could falsify the reading.  *
You measure then in the usual way:
LUNASIX F and LUNALITE:
First set the white index line for EV modification (15) on the green scale (13) to
"+3" in orderto compensate the loss of light due to the PROBE.
Press the red measuring button (6). After releasing the button, the value measured
at that moment will be stored automatically in the electronic memory of your system
exposure meter.
Next turn the computer ring (24) until the indicator needle is precisely at "0" or
the central LED (38) will light up. Read the shutter speed and f/stop combinations
suitable for your subject on the scales 17 and 18.
* The distance between grey-card and measuring aperture must not be greater than the diameter
  of the largest circle which you could draw on the grey-card.

LUNASIX 3:
                                                                               higherSetect on the LUNASIX 3 a DIN/ASA exposure index which is 9 digits
than the one suggested by the film manufacturers, e.g. take 27 DIN/ASA instead
of 18 DlNi50 ASA. The scale value indicated is set as usual at the yellow triangular
index and you can now read the tlme-aperture values suitable for your subject to
be measured at the upper end of the LUNASIX 3 calculator  ring.
Ground glass measurements
Exposure measurement in general
The MEASURING PROBE is ideal for ground glass measurements. All variations
such as filter factors, factor for bellow extension, and stray light are compensated
for.
The measuring aperture of the MEASURING PROBE is put in contact with relevant
area of the ground glass. External light must be eliminated by means of a black
cloth. lt is advisable not to measure at the corners of the ground glass as a decrease
                                                                                     aof light can be registered, which is essentially a feature of the lens. By using
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 the same illumination as the important
part of the picture to be measured. You then take measurei"nents ol the image of
the grey card.
LUNASIX F and LUNALITE:
You press down the red button (6), and the value measured at that moment will be
automatically stored in the electronic memory of the meter, when you release the

6

button. You then rotate the computer ring (24) until the indicator needle (4) points
 exactly at the "0" on the scale or the central LED (38) will light up. On ihe'scale
 (17) you now read the exposure time which is opposite t/1 on the aperture scale (18).
f/1 is your reading index for this measurernent with your chosen working aperture.
Extension factors due to bellows or filters used are automatically compensated for.

LUNASIX 3:
The film sensitivity is set 9 digits higher as described on page B. Set the indicated
scale value on the green mark of your LUNASIX 3 and read the exposure time at
f/2'8' ln this case the aperture index f/2.8 stands for the reading index and has
nothing to do with the aperture set at the lens.





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lf no time value is opposite of the reading index, set the next shutter speed to
it and then read the figure opposite of the green symbol. Then close or open
the lens aperture until the needle moves to that figure on the scale.

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O Measuring spots for ground glass measurement

Exposure measurement with 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 ybu can practically use the reading index for
  I      maximum aperture as described. For a smaller working aperture the computer
          ring (24) of the LUNASIX F and LUNALITE or (7) of LUNASIX 3 should be used.
         Rolatb ine computer ring to set the exposure time which was indicated now  I          opposite the f/siop on scale which equals your viewing lens aperture. Then read
          eiiosure time and f/stop for your taking lens on the scales as usual.
          Exposure measurement on reflex cameras with fully automatic diagrams
          Set the required working aperture manually and then take the reading.
        When measurement not 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:
                                                                                       be         1. Use the white side of the grey-card, this yields 21lr stops which will have to
            deducted from the value measured. For that purpose, you set the white index line
               (15) of LUNASIX F or LUNALITE on the scale (13) to -21/t.        il
         2. You measure with the lens wide open and compensate the difference in stops
   I         down to the working aperture by extending the exposure time accordingly.





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h
E.

This is easily Oone OV using the computer ring (24) ot the LUNASIX F or LUNALITE
            or (7) of LUNASIX 3: you rotate the ring until the exposure time indicated at the
             reading index is opposite the maximum aperture of the lens. Shutter speed and
             working aperture of the lens can be read on the scales as usual.
          You may also measure without filters and then correct for filter factor subsequently
               or set the ring for correcting factors (23) of LUNASIX F or LUNALITE.

              Determination of tndlvidual reading index
            1. By comparsion measurements:
               Set up your camera to face a grey-card and take a reading. Then null the meter
               with the computer ring and determine the shutter speed corresponding to
               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
                determined when 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 previously determined aperture 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 important part of the subject and null the
               meter again. Your reading inciex is the f/stop which appears opposite the ex-
                posure time previously determined.
               For future reference mark that index on the system exposure meter with one of
                 the stickers supplied (see illustrations pages 11 and 12).

              10
l
L

Example LUNASIX F or LUNALITE
Your film speed is 19 DlN. Your
MEASURING PROBE yields a shut-
ter speed of 1/rs sec. for the aper-
ture B set on your camera.  f /0.7*2/s
stops is then indicated opposite
r/rs sec. and this is your individual
reading index.

                                        11

Contrast measdrement
For this type of works adjust the LUNASIX F or LUNALITE for extended meas-
urement.
Subject contrast
Measure brightest and darkest spot either direct at the subject (see page 5) or on
the ground glass (see page 6). The difference of the scale values indicated is the
subject contrast expressed in exposure stops.
lllumination contrast
Use a grey-card for measuring the weaker general light and the effect light (see:
"measuring the illumination intensity" page 16). The difference in readings obtained
in those two measurements is the illumination contrast which you can modify in
case of need by shifting the lamps.
The admissible contrast depends on the job requirements, the film and the photo-
graphic paper used. Please refer to manufacturers, recommendations.

Denslty measurement
Density measurements can be taken of film negatives and transparencies using
the MEASURING PROBE and a light box. For accurate readings the light box must
be uniform in intensity, or a uniform section of the box used for measuring pur-
poses.

                                                                                    13

To measure the a6solute 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 measured over the very same spot on the light box and take a reading with
            the system exposure meter. Record the scale value as SN. The density of the film
            can be calculated from the formula:
r                                 D=O.3(So-SN)
|                change of one exposure value equals a density change of 0.3. The 1/r marks                 the scale are equivalent to a density change of 0'1'II           on=ach
             Example:
            Scale reading when measuring without film:  So = 18r/r
          When measuring with film on the light box: SN = 152/r
       D = 0.3 (18r/r -152/i:  0.3 x22lz = 0.3x8/s -  0'8
           The density of the area measured  is 0.8
             Density range of the film is the difference in density between the lightest area and
           the darkest area. For determining the density contrast, first take a reading at the
               iigntesi area (scale value S,o".) ind the darkest area of the negative (scale value
                  S.in.).
           The contrast K can be calculated from the formula:
                               K - 0.3 (S'o". - S'in.)            Depending on the requirements of the work in hand (enlarging of paper pictures,
               preparatio-ns for printings etc.) be sure to mind the instructions for the admissible
              density contrast.

              14

Measuremenf of illumination  intensity
 For measuring the illumination intensity   Exposure values     illumination intensity
 at very small areas the system expos-       LW/EV          lx              fc
 ure meter is often too big. For these
jobs you can employ the MEASURING      -3                   0.7            0.064
PROBE and a small grey-card. Place      -2                     1.4              o.'t25
the grey-card on the area of which the       -1                     2.8             o.25
 illumination intensity has to be meas-        0            5.5           0.5
 ured, so that it obtains the same illu-              1          11                   1
 mination as the subject to be mea-         2         222
 sured.                                           3          444
Subsequently point the measuring aper-        4         888
ture of the MEASURING PROBE to         5         175          16
the grey-card while observing that the        6         350          32
area to be measured will not be sha-               700          64
dowed. The distance should be close              1400        125enough to prevent the adjacent surr-                        7II        2800        250
ounding area falsifying the measure-        10             5500          500
ment (see footnote page 5).                        11                  1 1000          1000                                                                   I
The illumination intensities in Lux (lx)        12            22000         2000
and footcandle (fc) corresponding to        13            44000         4000the EV (exposure values) while sys-        14            88000         8000tem exposure meter set at DIN 18
(50 ASA) values can be seen from        15            175000         16000
the following table:                             16           350000        32000
These data are valid for a neutral grey-card with a luminance factor of 0.18.
16

Note:
     We also manufacture special luxmeters and footcandle meters such as PANLUX
        electronic and MAVOLUX electronic. They meet all requirements as to cosine
         correction an Vl" curves in the proper sense of the laws of physics. These meters
        are also ideal for all experts in lighting and illumination.





             lf repair or adjustment should ever become necessary please send your MEASURING
      PROBE carefully packed to
                   GOSSEN GMBH
                             Servicestelle B
                           NdgelsbachstraBe 25
                         D-8520 Erlangen
         or to the GOSSEN agency in your own country.

                                                                                       acces-I       to.expedite handling please send your MEASURING PROBE ony without
l'oI
It