Light meters
PHOTRIX SS exposure meter User manual
User manual for PHOTRIX SS exposure meter. 32 pages. Read the original PDF, download or print a copy without registration.
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- Brand
- Photrix
- Model / document
- PHOTRIX SS exposure meter
- Document type
- User manual
- Language
- Check the original document
- Pages
- 32
- File size
- 1.6 MB
- Category
- Light meters
- Document date
- Not specified in catalog
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Page 3 · Read text
TABLE OF CONTENTS
o
Pa(e
Setting PHOTREE SS for Emulrloa 8pecd.......... 2
Taking an Erporure Reading with PHOTREK SS 3
The PHOTRDK SS Readiag Metbod....... 5
Special Ligbt Conditions ........... 7
Film Rating Systems 9
Film Speeds ..................ll
PHOTRIX SS applied to Enlargement Control.. 16
Technical Description of PHOTRI)( SS.............. f8
PHOTRD( Light Measuring Equipment for
Studio and Dark Room ......... ..... 20
Determining Exposure with PHOTRD(
UNTVERSAL PHOTOMETER ....................23
Enlargement Control with PHOTRD(
UNTVERSAL PHOTOMETER ....................25
Leather Case for PHOTRIX SS......................,.....28
www.butkus.usView original page 3Page 9 · Read text
speed every time a reading is to be taken. It is en-
tirely possible, however, to operate PHOTRIX SS
in the conventional manner, disregarding the mov-
able glass and its index, by rnerely turning the ring
until the film speed number is on the tip of the field
indicated by the needle.
fn order to take an exposure reading, PHOTRIX
SS is aimed at the s6sns snd-in this aimed posi-
tion-the ring is turned until the index is on the tip
of the triangular field indicated by the needle. If the
glass has been set properly with the film speed figure
appearing framed by the red index (see figure
page 2) and if the ring has been set so that the tip
of the red index is exactly opposite the tip of the tri-
angular field (see figure page 3), then, the division
lines of the f :stop scale and of the exposure time scale
will be found to be lined up showing all usable com-
binations of f :stop and exposure time,
Note that, while the meter is in the aimed posi-
tion, it is not necessary to take any reading whatso-
ever but only to set the ring. This feature makes
PHOTRIX SS practically automatic in operation.
I{owever, PHOTRIX SS can also be operated in the
more conventional manner by noting the red figure
indicated by the needle and ietting the ring accord-
ihgly:';The red figures will, furthermore, be found use-
ful in taking notes on light conditions for future
reference.
For use with moving picture cameras, "frames
pir Second" figures are inserted on the exposure time
scale, figure "16" indicating normal operating speed.
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Exlremely Low Light
The high sensitivity of PHOTRIX SS allows to
take exposure readings at such low levels of illurnina-
tion as were formerly considered not to be measur-
able with pocket-type exposure meters. In spite of
this high sensitivity, the user may wish to take
scenes that are so poorly illuminated that the needle
of PHOTRIX SS shows only a very small deflec-
tion when used in the conventional manner. In that
case, it will be found more accurate to use what may
be described as a "target method." The target con-
sists of a sheet of white cardboard or paper and is
held near the subject to be photographed. The light
reflected from this target is rneasured by holding the
meter at a distance of about 6 inches from the white
surface. The reading obtained in this rnanner must
be multiplied by a factor of 4.
Another method to be recommended so as to ob-
'tain clear readings under extremely low light con-
sists in placing the meter hear the object to be photo-
graphed, pointing towards the main light source.
When using PHOTRIX SS in this manner, multi-
ply your meter readings by a factor of 10. I.t
For highest accuracy in timing exposures at ex-
tremely low light, see "PIfOTRIX Light Measuring Equipment for Studio and Dark Room" (page 20) II
and "Determining Exposure with PHOTRIX Uni-
versal Photometer" (page 23).
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In the proportionate systems,
a film-let us say-"24" is twice as fast as a
fiIm "12"
a film "12" twice as fast as a fit6 -"6rr
a fikn "24" four times as fast as a film "6" etc.
The dial of PHOTRD( S S is provided with a
proportionate as well as with an arithmetical scale
marked "W," and "Sch.", respectively, correspond-
ing to the best known rating systems. It is to be
understood, however, that this relation to other
existing systems refers only to the numbering
method and not to the testing method. The film
speed ratings given in the table below are not based
on any other published ratings but are arrived at
by actual practical tests in which the light was
measured with the PHOTRIX S S. Therefore, the
very best results can only be expected if the
PHOTRIX S S is used in conjunction with the
ratings given below.
The ratings supplied by film manufacturers will
mostly give satisfactory results, too, and whatever
differences there are between these and the PHO-
TRIX S S-ratings will seldom be large enough
to affect the picture perceptibly. It is to be noted,
however, that film manufacturers often rate films
differently depending upon with which exposure
meter the ratings are to be used. Other published
film speed tables, u'hen compared with each other
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PHOTRIX SS Applied lo
Enlcrgemenl Conlrol
A very valuable application of PHOTRI)( SS
consists in its use for determining the exposure re-
quired for the enlarging of negatives while thev are
in the enlarper. This application is made possibie by
the extreme sensitivity of PHOTRIX SS as well as
Ey tne location of its light intake at right angles to
the scale.
- Put an average negative in the enlarger, turn on
the enlarging lamp and focus in the usual rnanner.
Now, hold PHOTRIX SS as close as possible to the
entarging lens with the photocell pointing towards the
lens and regulate the iris so that the needle of the
instrument points at one
of the red figures, for in-
stance figure "5." Deter-
mine your enlarging time
just this once by means of
a test strip. Thereafter, for
all subsequent negatives of
normal contrast, enlarged
to the same size, merely
regulate the iris so as to
obtain again a needle
reading of 5 and grve the
sam e e x p o s u r e t i m e a s
before.
You may wish to shorten
or lengthen this exposure
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time wh_ich you can do by simply standardizing on
some other needle reading and employing the same
method as outlined before. You may, frirthermore,
wish to use a smaller or larger iris opening for the
actual exposure than the one arrived at bvlhe fore-
going method. To allow for a different iris opening,
you have to apply the square law which holds trul
with sufficient accuracy for enlargers as well as for
cameras. According to the -square law, an iris opening
of-let us say-f :8 requirCs 4 times the exposure
time of f :4, etc. i g''rij . +U-t' I)
_ Negatives of extreme contrast require slightly
l9nge1 e-xposure, flat negatives shorter e*posure thair
that indicated by the meter reading.
Changes in the enlargement size can be taken into
accognt by calculating methods using calculators or
published tables. Photographers who wish to avoid
calculations, however, will find it simpler to deter-
mine- the enlargement time once for each enlargement
size by means of a test strip.
It is understood that, in using the foregoing method
.of .enlarging control, you shoui.t guard agaiist stray
light entering the meter and influencing your meter
reading.
For greater ease of operation in enlargement con-
trol, see "PHOTRIX Light Measuring Equipment
for Studio and Dark Room" (page 2b) ,rrd ,,Err-
largement Control with PHOTRi{Univirsal photo-
meter" (page 25).
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Technicql Descripiion of
PHOTRIX SS
Readin! Rangle and Sensi/ivity: T c reading range
o{,an exposure meter is determined by thJ loweit
light condition at which the needle shows a clearly
noticeable deflection and by the highest light con-
dition at which the needle just abbut reaihes its
right-hand stop.
A properly designed exposure meter shows full-
scale deflection in the brightest light which is en-
countered in practical photography. As for dim
light, an exposure meter is the more useful and
universal the lower the light at which the needle
shows a clearly visible deflection. This low-light
limitation of an exposure meter is called "sensi-
tivity." It is determined by the movement, the
magnet and the photocell used in its construction.
Note that reading range and sensitivity have noth-
ing to do with the range of the scaleJ, just as the
maximum speed shown on the speedometer of an
automobile has nothing to do with the maximum
speed of the automobile itself. ft is understood
that a properly designed exposure meter has a
rqnge of scales sufficient to include all f :stops,
shutter speeds and film speeds. The actual pir-
for-mance 9f qn exposrrre meter, however, is soiely
indicated by its reading range and sensiiivity.
The reading -range of PIrOTRIX SS has its upper
limit at a light condition calling for l/500 secb'nd
exposure time at f :8, 23 SCH.
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The sensitivity of PHOTRIX SS (i.e. the lower
limit of its reading range) is given by its showing
a clearly visible deflection under light calling for
60 seconds exposure time at f :8, 23 SCH.
PHOTRIX SS thus covers a range extending from
1rl500 sec. to 60 sec. Its total reading range, there-
fore, amounts to 1 :30,000,
Ran6le of Scales.' F:Stop............1 to 32
Exposure Time: ,................,.1/2OO0to 60 seconds
Film Speed: J 11 to 38 SCH'
| 1.5 to 800 W.
F LenpthFramesof Needleper Second:Deflection:..............8l7/s" to 64
Meter Move.menf.. Ilardened steel pivots, sapphire
bearings mounted in bridge type brackets, needle
fully balanced and magnetically dampened to give
steady readings and to avoid undue wear duC to
oscillations. Zero adjustment on back of casing.
Manufactured by The Hickok Electrical fnstru-
ment Co., Cleveland, Ohio.FMagnet: Solid bar cobalt steel with soft iron pole
pieces. Magnets made from cobalt steel are so
strong that one will float in the air above another of
the same material.
Photocell: The photo-voltaic cell used in PHOTRI)(
SS consists of an iron disc carrying a light sensi-
tive deposit which, in turn, is covered by i ,.double
transparent metallic covering layer." (U.S. pat.
N o . 2 , 0 3 4 , 3 3 4 )
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PHOTRIX Meqsuring Equip. !ieh! menf for Sfudio snd Dqrk Room
PHOTRfXUni""ruol Phofomefer
M O D E L B
3 Measuring Ranges: O - 1 2 . 0 - 6 0 , 0 - 1 0 0 0 f t . - c d l .
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PHOTRIX
Cqlculqtors
PHOTRIX
Exposure
Calculator
PHOTRIX
Enlargement
Calculator
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Delermining Exposurewifh
i* PHOTRIX Universql Phofomeler
- The use of the PHOTRIX (Iniversal photometer
as an exposure meter is indicated for critical expo_
sures at very dim light. The sensitivity and thc
accuracy of the Photometer exceeds the one obtain-
able in p.ocket-type exposure meters because it is pio-
-vided with a photocell of larger diameter, with a
brgger and more powerful magnet and with a multiple
measuring range.
Photrix Photometer Model A and Model B are
both equally well suited for exposure determination.
Model A has a sensitivity four times as high as Model
B. It is, therefore, recommended in paiticular for
scenes of extremely low light,
Photrix Universal Phctometer gives the light read-
ing in foot-candles, the unit of illumination. io trans-
b_tgJhgg_t.adings into f :stop and exposure time, use
PHOTRIX Exposure Calculltor. Thii Calculatoi fits
into the lid of the Photometer and can easily be
fastened in it by thumb tacks.
__ To determine exposure, hold the photocell of the
l/ho-tometer Iacing the scene to be photographed and
rei9-the- light in foot-candles. Use the reading range
which_ gives the greatest needle deflection irittroit
throwing the needle off scale.
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.9et celluloid finger of Calculator on ftlm speed, hold
celluloid finger and turn disc until foot-candle'read-
ing is under center line of finger. Then, find all usable
combinations of f :stop and exposure time on lower
part of Calculator.
In some cases, it may be desirable to use higher
than normal exposure, for instance when using ultra-
fine grain developer, when using filters or when taking
scenes of very high contrast having in mind to under-
develop the negative. In such cases, set your foot-
candle reading not under the center line of the cellu-
loid finger but under the line marked "Double
Exposure,"
In other instances, you may want less than normal
exposure, for instance when taking a scene of very
low contrast. In such instances,. set your foot-candle
reading under the line of the celluloid finger marked
"flalf Exposure."
.If there is any danger of the photocell of the Pho-
tometer being struck by a strong light which is outside
the camera angle or if the main part of the scene has
an entirely different brightness than the background,
then, hold the photocell near the main point of inter-
est of the scene. In the same way, the Photometer
can be used to determine the contrast in the brightness
by scanning the different parts of the scene so as to
decide whether the latitude of the film will cope with
the contrasts of the object.
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Enlorgemenl Control with
PHOTRIXUniversol Photomeler
The PHOTRIX Universal photometer can be used
to great advantage to determine accuratelv the ex-
posure time in enlarging without the use of tlst strips.
In order to translate the readings obtained with the
Photometer into exposure timE in enlaiging, use
PHOTRIX Enlargement Cltiut"tor
follows: "rrJlio".ea ",
1. Place negative into the enlarger and focus as
usual. Make sure that the negative is masked ofr
in the carrier.
2. Ascertain the shape of your negative, i.e. its
ratio of width to length. The Enlargement Cal-
culator is calibrated for the following normal
shapes:
S Square,-.suqq,q.s l" x 1,,, LS/s,, x !s/6,,,
2 / 4 " x 2 / 4 , '
M Medium, such,as 3,/4,, x 4/4,,, 3f', x
4 / r " , 4 " x 5 " , 8 " x 1 0 '
O Oblong,-such _a.s-.L,,x \/2,,,l/s,'x 2t/r,',
2 / + " x 3 / q , , , 2 / r , , x 3 l ' i , 5 " i - 7 , i
L Long, such as 2/2,, x 4/4,,,3/4', x gf,t
ff ygur negative has an odd shape that does
not fall within the listed classifications, proceed
according to 3a.
3. Measure the short side of the entire projected
!"1qee on your enlarging surface and m6ve-cellu_
loid finger of Calculatoi until your shape of the
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negative frames the correct figure on the "Short
Side 2f ,Pro_jected Image" scale on the upper
part of the Calculator.
3a. If your negative has an odd shape, determine
the area of your projected image in square
inches. Then, set celluloid finger of Calculator
so that center line on tip of finger is on the cor-
rect figure of the "Area of Projected Image"
scale.
4. Determine paper speed from chart p. 2 7,. Then,
turn disc until your paper speed is underneath
center line of celluloid finger.
The Calculator is now set for your enlargement
ratio and for your paper speed, and the exposure
time for all enlargements of the same negative
size and the same magnification ratio can now
be determined without further changing the set-
ting of the Calculator.
5. Hold photocell of Photometer close to the lens
of the enlarger, excluding all extraneous light
that may strike the cell. Switch on the lamp of
the enlarger and take a foot-candle reading on
the Photometer. Then find your correct enlarg-
ing time opposite your foot-candle reading on
the lower part of the Enlargement Calculator,
The foregoing method will furnish perfect prints
with normal negative, normal in contrast as well
as normal as to subject matter. If a flat nega-
livs cralls for hard paper or for extra hard paper
and if a contrasty negative calls for soft paper,
use the corresponding dotted lines on the cellu-
loid finger instead of the center line.
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Leqther Cqse for PHOTRIX SS
The leather case for PHOTRIX SS is made of goat
skin with zipper fastener. To place the instrument into
the case, pull neck cord through hole provided in
back of case. If the meter is to be used, open zipper
and slide case back on neck cord sufficiently f ar to
uncover the dial.
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www.butkus.usView original page 31From the M. Butkus archive. Original publisher and archive notices are retained.
Check the model and edition against your equipment.
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