Omega C760 Instruction Manual page 15

With condenser enlargers, where the light is largely
uni-directional, there is relatively less ''scatter' and,
therefore, a projected image from a condenser
illumination system will have a somewhat higher
contrast. With diffusion enlargers, where the light
tends to be "scattered" before it reaches the black-
and-white negative, contrast of a projected image will
be somewhat lower.
As a general rule, the difference in contrast between
condenser and diffusion illumination, given the same
negative, is equal to about one grade of paper. That is,
the negative will enlarge satisfactorily on a grade 2
paper using a condenser enlarger, and a grade 3
paper when using a diffusion enlarger. This difference
in contrast can be corrected for in the initial processing
of the film.
The mixing chambers for the diffusion lamphouse
serve the same function when using the optional
variable contrast filters designed for use in the
attenuator slot. The light is then passed through the
film (color negative or transparency or black and
white negative) to produce the exposure on paper.
There is NO difference in sharpness between the two
forms of illumination because sharpness is a function
of the enlarging lens used. The only difference is in
contrast.
For the working photographer, the differences are
somewhat greater in terms of the pictures produced.
First, diffusion enlargers tend to suppress grain,
scratches and dust in the negative, thus reducing the
need for retouching. On the other hand, condenser
systems emphasize any minor defect. Second, the
print produced with a diffusion enlarger will show a
softer, more subtle, long scale of tones. There may be
a better balance of highlights and shadows,
particularly with contrasty subjects. In most cases,
pictorial and portrait photographers prefer the softer,
more pleasing gradation which results from printing
with diffusion enlargers.
(This difference in contrast does not apply to color
negatives since in color negatives, the silver is
replaced by dyes which absorb light instead of
scattering light. Since it is this scattering which
affects contrast, there is no difference in color
between diffusion and condenser enlargers.)
USING VARIABLE CONTRAST PAPERS
Variable contrast papers such as Kodak Polycontrast®
and Ilford Ilfospeed® Multigrade® can be printed
using the C760 Dichroic Lamphouse using either the
variable contrast filters recommended by the
manufacturer of the paper, or by adjusting the dichroic
filters built into the lamphouse. This latter procedure
should be tested first to determine correct settings
with various grades of paper. The following table can
serve as a point of departure, providing preliminary
settings subject to minor adjustments.
Kodak Ilford
Equivalent Equivalent
Dichroic Ilfospeed® Dichroic
Polycontrast® Filter Multigrade® Filter
Filters Settings Filters Settings
No. 1 OC/OM/24Y No. 1 OC/OM/54Y
No. 1% OC/9M/10Y No. 2 OC/OM/29Y
No. 2 OC/25M/4Y No. 3 0C/11M/10Y
No. 2% OC/36M/8Y No. 4 OC/35M/5Y
No. 3 OC/64M/12Y No. 5 O0C/74M/10Y
No. 3% 0C/138M/22Y No. 6 OC/127M/14Y
No. 4 OC/199M/45Y No. 7 O0C/200M/10Y
Polycontrast® is a registered trademark of Eastman Kodak Company.
lfospeed® and Multigrade® are registered trademarks of Ilford, Inc.
For printing with variable contrast papers with the
C760 diffusion lamphouse you can use the optional
accessory Variable Contrast Filter Kit (Catalog No.
429-376.)
YOUR FIRST BLACK AND WHITE PRINT
The basic variables of black and white printing are ex-
posure and contrast. Exposure of your print must be
correct, otherwise your picture will be too light or too
dark. The contrast of your paper must match the con-
trast range of your negative. Too much contrast will
result in a harsh, excessively contrasty print with a
"soot-and-whitewash"' appearance. Too little contrast
will produce a print lacking "snap."' Contrast is in-
dicated by numbered designations, with 1 being least
contrasty, 2 or 3 being considered ''normal'"' and 5 be-
ing the most contrasty grade. When using variable
contrast papers, such as Polycontrast, the printing
filters used to provide the various contrasts have
similar grade designations. And, with proper adjust-
ment of the C760 Dichroic Lamphouse, you can pro-
duce variable contrast by varying the filtration, as
shown in the chart on this page.
The best way to determine correct exposure and con-
trast, at least at the beginning, is to make a test strip.
1. Select your negative and dust carefully with a
soft, camel hair brush to remove any dust or dirt.
Place the negative into the film carrier of your
Omega enlarger.
2. On the Dichroic Lamphouse engage the white light
lever or place all the filter controls at "0" to remove
any possibility of accidental filtration. Turn on the
light in your C760 Lamphouse and raise the
enlarger carriage so that you have an image of
about 8''x10" on your easel. Now focus and
compose your picture.
3. Set the aperture of your enlarging lens to f/8.
4. Take an 8"x10" piece of cardboard to useasa
mask. Now turn off all light including your
enlarger. The only light should come from your
safelight. Place a sheet of 8"x10" enlarging paper
(you should get No. 2 or 3 contrast) in your easel
on the baseboard of your enlarger.
5. Place the cardboard mask over the enlarging
paper in the easel and cover the entire sheet ex-
cept for a strip about 1%" wide.
6. Turn on your enlarger. Set your timer or use a
clock to time an 18-second exposure, moving the
cardboard mask every three seconds to uncover
an additional 1%-inch strip of paper.
7. At the end of your 18-second exposure, turn off
your enlarger. Place the print in your developer
and develop fully, following the recommenda-
tions for your particular developer. (With Kodak
Dektol, for example, develop for two minutes at
70°F)
Important: If your print looks too dark, resist the
temptation to remove it from the developer
before the proper time is up. If your print is too
light, remove it at the proper time.
Wash and fix your test print normally.
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