Rebikoff Color Temperature Meter User manual

Principle
The latest experiences in color phofography have confirmeci a fact established
by Newton yedrs dgo: The color.ol any object depends on the color of the light
used. For insta,rce, a grey object lighted with red light looks red, a yellow ob-
ject lighted with blue light looks black. The ligth generally used in photography
dppears white to us lf we compare various photographs we easily notice slight
di{ferences in color. In real life we are not aware of such differences, whereas
color film is extremely sensitive to the colors present in a scene
Color differences of daylight depend on the position of the sun in the sky, at-
mospheric conditions, the location of the photographer.  lJ artificial light is used            t
there is the inf luence of the type. of lightsource and voltage. Such di{ferences
can be practically expressed in degrees Kelvin.
Kelvins are centi-degrees above the absolute zero point and evaluate the color
temperature of a lrghted body. This temperature indicates the spectral compo-
sition of radiated light. At a low temperature, for instance 1500c Keivin, light  is
red (red hot iron), at 5900o Kelvin it becomes practicaliy white (white hot iron,
sun) and above this temperature it becomes blue.  lt is therefore necessdry io
measure the ratio of red and blue of the lightsource (incident light), in oi'der to
determir\e its co;'ri' t€flrPgl'<irur€.
The REBIKOFF enables you to do this easily and accurate:y by means of an elect-
ric bridge with two photoelectric cells covered by filters, one Sensitive to red,
the other to blue. An ootical poterrtiometer restores the balance between red
                                    and blue by a microammeter which
                                               is a very sensitive coil. BY ad-
                                                 justing this coil the needie can be
                                        balanced in the middle, between
                                    the red and blue areas and the
                                           dial then gives a direct reading
                                        of the color temperaiure in o Kel-
                                                                   v in.
                                                         P rote cted by  a n  a tt ra ct ive ly  d e-
                                       signed plastic case the meter is
                                           compact, lightweight and extremely
                                          simple to operate. Accurate redd-
                                       ings are guaranteed by its  fine
                                       Swiss precision works.
                                      With the REBIKOFF the color pho-
                                        tographer can avoid bluish and
                                         reddish pictures. lt  is the ideal
                                    pocket instrument for control ol
                                            color balance.
                            www.butkus.us

lnstructions for use

 A. Delermining the color lemperature.
 1. Hold the meter in the place of the subject to be photographed and direct the
   dial face (11) (which covers. the two photoelectric cells and filters) perpend-
    icularly towards the lightsource, making sure that your fingers do  not
   cover  it.
 2. Turn the dial (8) unril the needle (2) (which may be viewed from the front or
   the rear of the transparent part), (5) ipoints exactly  to,,. the black triangle  (3)
   between the red and the blue strips:l Align the white dot (4) on the front sur-
   face with the black triEngle (3) to prevent parallax:
3. Read the color temperaiure in o Kelvin on the'scale (10) as marked by the
   yellow arrow (9).
4. lf the yellow triangle  (7) opposile the yellow arrow (9) points to one of the two
   figures sun (1) or electric-b\tO- (O), you may use daylight film (5900 o Kelvin)
   or indoor film (3200o Kelvin), as the color temperatur of the lightsource cot-
   responds with the one for which the film is manuiactured    the desirable.'                                                                        -   solution in color photography.
5. The needle (2) reacts only, if the light is strong enough for taking color pho-
   tographs,-oih-erwlaelo-u-tan   slill deie-rmire- tti6.colorTempbrature-Ay  irring=-_- --
   ing the meter closer to the lightsource, although the reading may be less
   accurate. Fluorescent light may not give a precise reddtng.
B. Choosing the right filter.                                                   i
1. After the color temperatule  in
  o Kelvin is measured (A), i ref er
  to the   f ilter charts. At lef,,t there
   is a color temperature  scale
   identical to that of the REBIKoFF
  and lo the right you find all
   conventional color lilms with the
   filters of the same'mdnufactufe
   in the columns below. In addititbn
  ihe Harrison lilters are listed.ri
2. On the left of each filter number
  the correction factors are given,
  which correspond with the lens
  stop intervals. For instance, cor-
   rection factor 1 means that lens
  stop F/8 has to be corrected to
   F/5,.6; correction factor 2.5 means
  correcting F/8 to a lens stop
  between Fl4 and F12.8.

5. A zero in the filter column indicates that you need no filter at all.
      4. lf you find no filter on the same line as the determined color temperature,
       use the nearest one above or below. This solution is quite satisfactory for
          slight differences. Infrequently there will be a greater difference in which case
            it is recommEnded to change the light or wait for another time of the day,
        in order to obtain a perfect'photograph (see also C).
       5. There are no filters needed for electronic speed lights or strobe lights, as
         recent models give a perfectly white light of 5900 o Kelvin and never change
         their color temperature.
     C. Adjusting the lightsource.
         lnstead of using color correction filters (B) you may prefer to adjust the light
       to the color temperature ol your film:
      1. Turn the dial until the white arrow (9) points to the color temperature of your
           lilm.
      2. With daylight film (59000 Kelvin) the white triangle (7) opposite the white ar-
      row points to the ligure o{ the sun, with indoor film (32000 Kelvin) to the
        ligure of the electric bulb.
      3. Direct lh-e dial lace -OJ-rhe meTeT-I-tTi-lowdrdrttTe lightsoufce, mdking sure rirar
        your lingers do not cover it. lf the needle (2) moves into the blue or red area
          (5), i.e. the color temperature of the lightsource is higher or lower than the
      one your film is made 1or, your picture will be rendered bluish or reddish.
      4. Daylight: Wait for the best time of the day (in summer early morning and late
        alternoon; in winter noontime). Choose also the most favorable angle towards
        the lightsource according to your subject and the atmospheric conditions, so as
       to reach the same color temperatufe as your film.
      5. Artilicial light: Change the resistance, if possible, or use other lights until
      you reach the same color temperature as your lilm.
     D. Special lnstructions:
      1. While the REBIKOFF may be exposed to very strong light, it is quite sensitive
       to heat. Temperatures above 120o Fahrenheit may damage its photoelectric
tt       cells permanently.
      2. The color temperature meter is sturdily built, but is is of course in your own
        interest to treat it with best possible care, as any precision instrument may
     be impaired by falls and unnecessary shocks.