When a diffusion enlarger is used, negative defects
are not recorded as clearly in the print, compared to
condenser enlargers. There is an apparent overall
“softening” of the image sharpness and a reduction in
image contrast.
Most of your negatives can he enlarged equally well
with either a condenser or diffusion enlarger; however,
for certain work the choice of enlarger may be an
important factor.
The characteristics of a diffusion enlarger are as
follows:
It should be used for printing negatives that have
been retouched.
It subdues negative defects and grain.
It has less image contrast than that produced with
a condenser enlarger.
It is not suitable for making large prints due to
the softness of the image produced.
Diffusion enlargers should be considered for use in
portraiture and when the negatives have been retouched.
CONDENSER-DIFFUSION ENLARGERS
A condenser-diffusion enlarger or semidiffusion
enlarger is a compromise between the two extremes of
condenser and diffusion. A condenser-diffusion enlarger
uses a diffusion (frosted) bulb and condensers, or a
diffusion bulb with either a diffusing glass over the
condensers, or else one of the condensers itself acts as
the diffuser.
A condenser-diffusion enlarger has the advantages
of a diffusion enlarger to reduce the effects of negative
defects, silver grain structure and dust, and it also uses
the condenser system for speed and uniformity of light.
The enlargers in general use by most Navy imaging
facilities are the condenser-diffusion type. They use
frosted or diffusion bulbs with or without a diffusion
screen placed above the condensers.
ENLARGER LENSES
As with a camera, the lens of the enlarger is the heart
and should be high quality and reasonably fast. It is
senseless to buy high-quality lenses for the camera, then
nullify the quality they provide with an inferior
enlarging lens; however, a quality camera lens is not
suitable for enlarging. Even a moderately good
Table 11-1.–Enlarging Lens Focal Lengths for Various Negative
Sizes
Negative size
Lens focal length
35mm
50mm
120 (2 1/4 x 2 1/4) (6x6cm)
75mm
120 (2 1/4 x 2 3/4) (6x7cm)
105mm
4 x 5 inch
135-150mm
enlarging lens is better for enlarging than most camera
lenses.
The focal length you use with an enlarger should be
based on the size of the negative to be enlarged. (See
table 1l-1.) Generally speaking, the focal length of the
enlarging lens for a given negative size should be the
same as a normal-focal-length lens used by the camera
for the negative.
While it is not necessary for the lens to cover the
full area of the negative, the longer the lens focal length,
the less magnification at a given lens-to-paper distance;
therefore, you must have several lenses of various focal
lengths available for your enlargers when you want to
make large prints from small portions of your negatives.
Because an enlarger produces an image from a flat
field (the negative) onto a flat field (the paper), depth of
field is not a factor, except when distortion control
(discussed later) is used. An enlarger lens can usually be
used at large f/stops; however, when an enlarger lens is
used at its maximum aperture, there may be some falloff
of light at the edges of the circle of illumination.
Therefore, an enlarger lens is usually stopped down one
or two f/stops from wide open. Like a camera lens, when
an enlarger lens is used at very small apertures, there is
a loss of image definition due to diffraction.
ENLARGING PROCEDURE
The darkroom design, the equipment, and the
arrangement for enlarging are basically the same as for
contact printing. The safelights should be appropriate
for the type of paper being printed. The size of the prints
may require larger trays and greater amounts of solution,
but they should be set up in the sink the same as for
contact printing.
To produce good enlargements, you need good
negatives, a clean enlarger, clean printing filters, correct
exposure and development, and careful processing and
finishing. Although most negatives can be printed by
projection, there are a few desirable characteristics. A
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