Light meters
GE Exposure Meters instructions User manual
User manual for GE Exposure Meters instructions. 17 pages in English. Read the original PDF, download or print a copy without registration.
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- Brand
- Various brands
- Model / document
- GE Exposure Meters instructions
- Document type
- User manual
- Language
- English
- Pages
- 17
- File size
- 1.3 MB
- Category
- Light meters
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- Not specified in catalog
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Page 2 · Read text
I N S T R U C T I O N S
GENDnAL@ r,DCTRrC
30 EXPOSURE METER
6tt,"'JllAil,ru ek ,*'q.a:t K"*
rE FOR UOST FOOT.CANDtESilINtrui' RECOTilENO€O
TASTS
TO USE INSTRUMENTAS A LIGHT METER' REMOYE THE
HOOD AND READ FOOT.CANDLESON THE RED SCALE
Light Meter &.lq ShowingMinimum lllumina-
tion Values Recommendcd
GEJ-zsgsView original page 2Page 3 · Read text
DETAILED INSTRUCTIONS
The General Electric exposure meter is a precision
instrument designed for use not only as an exposure
TABLE OF CONTENTS meter to be used in correctly setting camera aperture
and shutter time, but also for use as a densitometer,
Page a light meter, and as a guide in portrait and dark- Simplified fnstructions. I room work.
Detailed fnstructions The degree of satisfaction received from the
fmportant Factors in Proper Exposur€. . . . . 1 device depends upon its correct use. For that
IVlethods of Determining Ligfrt Value Read- reason, the user should read this complete book of
r n g s . . . . . T general instructions carefully. Some of the material
E x a m p l e s o f I I o w t o T a k e R e a t l i n g s . . . . . . . . 1 4 iontained in the simplified instructions is amplified
Using the Calculator 15 and supplemented with other information which is
F o r M o t i o n P i c t u r e s . . . . . . . 1 5 .,...siry for obtaining the best possible results.
Use in the Dark Room. lT
Method A for Street Scenes at Night Zz
M i s c e l l a n e o u s l f s e s . . . . . . . . . . . 2 IMPORTANTFACTORSIN . . . . . . . 2
Hints for Satisfactory Operation. . . . .. .. . .. 2T PROPEREXPOSURE
R e p a i r I n s t r u c t i o n s . . . . . . . . , . . . . . . Z g The proper exposure of negatives for best results
depends on using the correct value of film emulsion
spied (obtained from the film-speed rating sheet),
the illumination available (exposure meter pointer
indication), and the lens aperture and shutter speecl
(obtained from the exposure meter calculator).
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FILM SPEED 2.O
Figure I shows a curve of the relative responseof ; 1 6
various films it to light. From this curve can be C 1-2seen light is 3 that a certain rninimum amount of
required value 1 to affect the filrn at all. Above this ! o a respondsthe film more more light I and as the 2increases until a point is reached beyond which S o.a z-,2'
the film will no longer respond-this illustrates the ctz o
term "6lm latitude." After this last point has been 1 0 1 0 0 1 0 0 0 1 0 0 0 0
reached, further exposure does not increase the Re.lative a,xposufe
density of the film. Fig. 1
Imaginary emulsion curves Film speeds are values which give a measure of
the relative responsiveness to light of the many is small, the exposure can be increased or decreased
different film emulsions. The C-E exposure meter is materially without harmful results. No hard and
calibrated so that the film is always exposed to a fast rule can be given, however, since this latitude
definite point on the curve section bracketed in is entirely dependent upon the range of the particu-
Fig. l. This point on the curve has been determined lar film emulsion. In spite of this range, where it is
to give the density of negative usually desired. If desired to emphasize some particular part of the
more dense or less dense negatives are desired, the object to be photographed, the meter reading
user should adopt by experiment a factor which should be taken close to that part.
gives this result. All of the above applies to black and white film.
From this curve it can be seen that the relative Without exception when using color film, the ex-
exposure in black and white films may be varied posure meter should be followed absolutely and the
over wide limits. Where the contrast over the scene reading taken close to the subject whenever pos-
sible.
3View original page 4Page 5 · Read text
^ No special instructions are necessary with the sheetgiving up-to-date ratings determined especially
G-E exposure meter for use with coloi film. The for your General Electric exposure meter.
same principles apply to both color and black and
white photography. The only difference is that a EXPOSURETIME
more accurate measure of illumination, either on or The time during which the image is cast on the
coming from the scene, is necessary to obtain good film is regulated by the shutter speed and is known
color pictures. The General Electric exposure meter as the exposure time.
reads the illumination with sufficient accuracy to The time values used on the G-E exposure meter
prodr,rcegood results with color film using the film are for shutters in correct operating condition.
speeds given. It is of great importance to get as Since there may be some variation in camera
close as practical to the part of the scene to be equipment, it may occasionally be necessary to
most truly represented. Good results, however, are modify actual settings for individual cameras. It
usually obtained by pointing the exposure meter should be understood, however, that any such
from the camera position if impractical to get corrections should be made only after a large
close. number of pictures have been taken under a wide
To encourage standardization, and in recognition variety of conditions.
of the widespread acceptance of the film-speed
rating system established by the Weston Electric THE (f) VALUE
Instrument Corporation, the General Electric The (/) value of a lens is defined as its focal
Company has adopted this system of rating films length divided by the diameter of its effective
for the G-E exposure meter. Films are tested in the opening. The focal length of a lens is the distance
sensitometric laboratory at the General Electric in- from its effective center to the film when the
strument factcry in West Lynn, Massachusetts. camera is focused for infinity. The eflective opening
_Film-speed rating sheets are issued periodically. varies as the square of its diameter and governs the
You can obtain from your dealer a G-E flm-speed amount of light which the lens allows to pass to the
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film. Usually the lens mount permits easy adjust- METHODSOF DETERMININGment of the (/) value.
other things With remaining constant, the smaller LIGHTVALUE READINGS
numbered (f) values permit more light to pass There are two recognized methods of determining
through the lens to the film. It is customary to say light values. One is based on measuring the- light
that the lens has a speed rating of the smallest (/) refected from the object to be photographed; the
value (largest opening). other, the light falling on the subject. The latter
The table below gives the relative illumination method is extremely accurate and especially useful
necessary for correct exposure when the shutter in very low light intensities.
speed is kept constant and (/) values are changed.
REFLECTEDLIGHT METHOD
Relative To use the G-E exposure meter by the reflected (f) Illumination
Value Required light method, the readings are taken with the
't protective hood extended in the operating position.
1 The hood restricts the light falling on the light- t . 4 2
2 A+ sensitive cell to a definite area as shown diagram-
2 . 8 8 matically in Fig. 2. The angle of light entering the
'i.4 1 6 exposure meter is narrower in a vertical direction so
5.6 32 that unwanted sky light and strong ground glare
8 61 are excluded. The foot-candles indicated represent
1 1 . 3 r28 illumination available for producing an image on
1 6 256
22 484 the film.
32 r024 To extend the directional hood to the operating
4+ 1936 position, hold the body of the instrument with one
64 4096 hand and with the other slide the hood until it
6 www.orphancameras.comView original page 6Page 7 · Read text
-=----_\---
: n ; r [ ) i u l t o p o s i t i o r ra s s h o r t n i r r I . ' i e .] . S t r r c ] r ' 1 . ' qI .,
. i r n l r l i f i , ' ,i in s t r r r t ' t i o r ) si t n c ll c a r n t h c n a r n c s o I t h c
u ] ) p t ) r t a r r tJ r i r r t so I t ] r ( . c x p ( ) . s r l r cr r r c L e r I o r f L r t r r r c
r t ' l r r c t ) r ' t ' . U i
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To Take Readings
When taking readings rvith the G-E exposure
rneter it is pointed tou'ard the object to be photo-
graphed as is the canlera.ln most casesthe read-
ing can be taken from canrera position. Hor.t'el'er.
rvhereanv sineleobject is of more importanceit is
r''ell to approachas closeas possibleto this object
before taking the reaclings.Taking the reading is
the most important step in determiningcorrect ex,
posure.Any exposuremeter is a tool. and judgment
and experiencert'ill add to its usefulness.
For averagelight conditions the hinged cover is
openedand readingsare taken on the red.0- 75 foot-
candle. scale. When the light becomesso bright
that the needledeflectsofT scale.the hinged cover
shouldbe closedand the readingtaken on the black.
0 7i0 foot-candle.scale.The hinged cover acts as a I)ir-r. I
ten-to-one multiplier and should be used either \ l r . l t ' i ' 1 i l | 1 r , 1 1 !J 1 r - r o 1 l
closed or open as light conditions and pointer
position indicate.
lorv light intensities where reflected light values
INCIDENTLIGHT METHOD are too low to give readableindications.Renrove the hood as shown in Fig. 4. Foot-candlesare rcad
One of the features of the General Electric ex- on the 0 75 foot-candlescale.Thc light fallinq orr
posuremeter is its use as a light meter at extremely the subject should be measured.This rnethod is
I ( ) l lView original page 8Page 9 · Read text
particularly useful for pictures taken inside in
poor illumination where it is possible to measure
the light around the subject accurately.
For example, if a subject is lighted with an
intensity of l0 foot-candles, the reflected light
reading will be very small. When the instrument is
used as a light meter to measure incident light,
however, l0 foot-candles is a readable and accurate
indication.
A bright object reflects more light than a dark
one, is brighter to the eye, and should appear
lighter in the 6nished picture. If the same amount of
light falls on a dark object and a light object, the
same setting of the camera will give them their
correct relative appearances on the negative. A trial
by the most skeptical will prove that the incident u." if'5ioi,,*ntlight method gives correct camera settings since
falling on the object should be used. Readings arethe reflection coeffrcient of the object will cause it
made on the red, 0-75 foot-candle, scale. The ex-to appear properly in the photograph.
posure is obtained from the calculator in the usual
way, but the camera should be set for l0 limes thisTo Take Readings
exposure.
When used in this manner, the exposure meter For example, assume the situation shown in Fig.
should be held at the object so that it points half 5. The reading should be taken when the foot-
way between the main source of light and the candle meter is placed at the object and pointed in a
camera. In all cases the average value of the light direction half way between the camera and the
L2 13
www.orphancameras.comView original page 9Page 10 · Read text
main source of illumination. Assume a reading of l0 object. The correct way to make this reading is from
foot-candles and a film speed of 16. If the shutter a position near enough to the object so that the
speed for an (f) stop, say (f)4.5, is desired, set l0 white background is a negligible portion of the total
foot-candles opposite (f)4.5 and read lll0 second field taken in by the exposure meter.
opposite a film speed of 16. Multiply lZl0 second Another example is found frequently in indoor
by l0 and the result, one second, is the shutter photography where the artificial illumination covers
speed to be used. Or, if it is decided to use one sec- intensely only a small area. From the camera posi-
ond with a film speed of 16, set the film speed of l6 tion the exposure meter would include this well-
opposite lilO of one second and read the (f) stop Iighted area plus a large percentage of poorly
opposite the indicated foot-candle value. In this illuminated background. Thus, the exposure meter
case, the (f ,1stop opposite l0 foot-candles is (f )4.5. would indicate a low average illumination and over-
This method can be used for either still or exposure of the negative might result. In this case, as
motion-picture work. in the above example, the reading should be made
from a position near the main object.
EXAMPLESOF HO\T TO TAKE
READINGS USINGTHE CALCULATOR
Assume that a picture is to be made of a small See simplified instructions.
gray object which is directly in front of a large
white and approximately twenty background feet FOR MOTION PICTURES reading taken from camera. A the camerafrom the
position would result in a badly underexposed image In this case the shutter speed is a set value for
of the main object. The influence of the large white the particular make of camera. The speeds vary for
background makes the average light intensity over different makes of cameras as shown in the table on
the scene much greater than that over the main the next page.
L4 1 5View original page 10Page 12 · Read text
Put the exposure meter with hood off in the (u.) For a given table setting (distance from lens
position previously taken by the printing frame, to printing paper) determine the proper enlarging
and place this standard negative over it so that the time for a negative by experiment. Then, hold the
meter will read the actual foot-candles that reach meter at the lens of the enlarger as shown in Fig. 6
the paper. Another film giving a reading of twice the and read the light coming through the negative.
foot-candles will require half the printing time. For the same table setting the enlarging time for
If the greatest accuracy is desired, it is advan- any other negative can be determined by comparing
tageous to block off a section of the meter cell the readings at the lens. Remember the rule: The
opening and explore the negative to get the reading more light, the less time. Fifteen foot-candles needs
on the section that is of greatest interest. A master I 13 the time that five foot-candles does, and so
negative may well be filed with a record of the foot- forth.
candles and time to produce satisfactory prints on (b.) Another way is to take a reading on a
various papers. With this information it is easy to negative as shown in Fig. 7 after having determined
reproduce any given set of conditions at a later the proper time for a given table setting. When it is
date. desired to print another negative in the same
AS A GUIDEFOR ENLARGING enlarger with the same setting, read the new negative as in Fig. 7 and determine the enlarging
Use as for contact printing except insert the time in the enlarger by the ratio of the readings.
ne-gative in the enlarger and read at the printing Always remember that more light requires less
table. exposure.
Inasmuch as enlarging papers are much more If the table is moved, this also affects the printing
sensitive than printing papers the light from the time, since the image is brighter when small than
enlarger is likely to be too low to give good read- when large. lf a 2X enlargement takes 30 seconds,
ings on the meter. Here are two ways to overcome a 4X enlargement will take 4 times as long or two
this difficulty. minutes.
1 8 1 9View original page 12Page 14 · Read text
is a tableA METHODFOR STREETSCENES the home, office, and factory. Following
AT NIGHT tasks.showing the amount of light necessary for various
Assume that the meter, even with hood removed,
gives no reading when the only illumination at RECOMMENDEDMINIMUM FOOT.night is a street Iight. get Then as close as possible
to the light, for example l0 feet, point the meter CANDLES
toward the light, and read the value. Suppose the Under l0 foot-candles-corridors, auditoriums,
reading is two foot-candles. This is the lncident railway platforms, bulk storage, coal and ash han-
light l0 feet away. To obtain the correct exposure dling, foundry charging and casting floors.
with this incident light use the calculator in the rough receiving, and l0 foot-candles-shippingregular way and multiply the time setting by l0 welding, assembly, work, machine work and as bench
described on page l3 for the incident lighl method. glass blowing, paint manufacturing, leather tanning
For other distances, such as 100 feet, the light will and stretching.
be reduced in proportion to the square of fh. dir-
tance. For ."i-pI., two foot-candles at l0 feet 20 foot-candles-knitting machines, printing presses,
will be 0.5 foot-candles at 20 feet and 0.02 foot- electrotyping, light colored leather and cloth
candles at 100 feet. fabrication, rubber products fabrication, retail
stores.
MISCELLANEOUSUSES 50assemblyfoot-candles-drafting,and inspection, handfine machinesewing, jewelrywork,
Since with the hood removed the G-E exposure-useful repalrlng.
meter becomes a light meter, it has many 100 foot-candles-proofreading, automobile body
lnRlications outside the field of photography. inspecting, dark leather cutting and grading,
One interesting use is for checking illuminalion in tobacco grading, hospital operating tables.
22 23
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meter held about five inches away from the surface.
remove the blotting paper. take another reading in
the same position and obtain the reflection factor
by direct ratio.
For example.aisume that the white blotting
paper has a reflection factor of 77 per cent (fairly
representativeof standard white blotting paper)
and that the reading taken with the blotting paper
is l0 foot-candlesand without 5 foot-candles.The
reflectionfactor of the surfacewould be the ratio of
5 l0 of 77 per cent or about 38 per cent. It must
be remembered.hor+'ever,that this method is an
approximationand can be used for measuringsur-
laces that almost entirely diffuse the light that is
reflectedfrom them. The measurementof reflection
coefficientsof bright objects such as mirrors re-
qurresmore apparatus.
\ l t ; , - ' ' , , , r - , t ' i ,,t),, , ' , , , r l r l r r r r 'l ' TRANSMISSIONFACTORS
To check the transmissionfactor of any trans-
REFLECTIONCOEFFICIENTS parent object it is necessarvonly to place the -l-o
cletcrnrincreflectioncoefficicntsplacea sqLrare instrurnentwithout the hood in a reasonablycon-
foot of clean rt'hiteblotting paper of knorvn reflec- stant source of light and take a reading. Then
tion lactor against the surfaceto be nreasuredas place the transparent material so that it com-
.ir,rrtnin Fig.8. Take a reading rt'ith the exposure pletely covers the cell opening ancl takc another
' l ! . ,
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the full open position to prevent part of the light
from being cut off. REPAIRINSTRUCTIONS
6. Care should be taken not to obstruct the
light falling on the cell surface. Be sure that your If repairs or adjustments become necessary,
hands or clothing do not cover part of the opening your exposure meter will be repaired promptly, if
in the hood which allows the light to strike the forwarded directly to the Geniral Elictrii iom-
cell. pany, 40 Federal Street, West Lynn, Massachu-
7. When not using the meter, the hood and setts, pQstag-eprepaid. Or, if you prefer, it may be
multiplier should be closed to give maximum pro- returned to the dealerfrom whom il was purchised,
tection. and he will return it to the factory. Repalrs and
adjustments will be made promptly, and the in-
8. If the hood becomes difficult to open or close, strument will be returned to the iender, charges
it can be made to work easily again by marking collect on delivery. A suitable tag with the sende-r's
with a soft lead pencil or graphite on the guides name and address should be tied to the metal ring
inside the hood and the spring balls on either that is provided for the.purpo.se of carrying th;
side of the instrument. exposuremeter on a neck band.
9. If repairs become necessary, see the inside - Be sure to _print name and address plainly on
back cover of this publication. the tag and alio on the outside of the iackage.
- Exposure meters should be carefully-damagedpaiked
when being returneJ since they may be
beyond repair, if roughly handled, when ina-de-
guately packed. The instrument should be "floated"
!n crumpled paper (do not use excelsior)r) inin aa boxbox
havinghaving dimensionsdimensions 88 bvbv 88 by 8 in., andd thethe tbox
plainly marked "FragilrHandle with Care."
www.orphancameras.comView original page 17From the M. Butkus archive. Original publisher and archive notices are retained.
Check the model and edition against your equipment.
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