Consider safelight illumination before you paint a
darkroom. Paint ceilings flat white for use with indirect
safelights. The walls should be a light color—preferably a color
similar to that transmitted by the safelight filters. A neutral
color, such as light tan or buff, is suitable in most cases. Paint
the wall area immediately behind each enlarger a flat black to
avoid reflection of white light from the enlarger onto the paper.
Flat black paint is also recommended around light locks to
prevent unwanted light from entering darkrooms. An all-black
darkroom is best for preventing fog or super-additive exposure
in some applications, such as copying and duplicating.
KODAK Utility Safelight Lamps provide good indirect
illumination when they are hung with the filter side facing the
ceiling. In large rooms with white ceilings, place no more than
one lamp for every 64 square feet (6 square meters) of ceiling
area. For the work areas where you need more concentrated
light, hang KODAK Darkroom Lamps from the ceiling, or use
KODAK Adjustable Safelight Lamps with ceiling, wall, or shelf
mountings. You can use a number of these lamps (with the
correct filter and bulb) if they are at the proper distance from
the photographic material and are spaced at least 8 feet (2.5
metres) apart.
Don’t put a direct safelight where it will shine on an
enlarging easel and make dodging and cropping difficult.
Improperly placed safelights can also interfere with exposure
calculators, and will decrease the safe time during which you
can safely handle the paper in this location.
If your operation is large and you have a number of
darkrooms for the same application, be sure that the safelight
illumination is uniform from room to room. Similar wall paint
and spacing of the safelights will provide uniformity. Operators
can then work in any of the rooms under the same lighting
conditions, and their judgement of quality under similar safelight
conditions should remain consistent.
SAFELIGHT PRECAUTIONS
Many factors can cause unsafe illumination: an incorrect
safelight filter, a faded or cracked filter, incorrect bulb wattage
(too high), safelight location, or too many safelights. You can
also experience light fogging from other sources; such as light
escaping from an enlarger head, lighted dials on equipment
controls, or non-opaque darkroom construction materials. For
example, pinholes between the darkroom space and lighted
areas can admit visible light, or plywood that appears opaque
may admit infrared illumination. Even when you use the correct
safelight filter and bulb, and observe the recommended safelight
distance for the product, you should still test your darkroom
conditions to be certain they are safe for the length of time that
the photographic material will be under the safelight. Use the
safelight tests described in “Test for Black-and-White Papers,”
and the “Tests for Other Photographic Materials,” to determine
a safe time for your darkroom conditions, and limit your
safelight exposure to that time.
Excessive exposure to safelight illumination may show up
only in the image area of your print, because that area receives
additional exposure from the enlarger. This means that you may
not recognize a change in image quality caused by excessive
safelight exposure unless you perform a safelight test.
Safelight tests that involve partially covering a piece of
photographic material with an opaque object (such as a coin)
and then exposing the material to safelight illumination can be
misleading. They test only for fog—not for the added effects of
safelight and enlarger exposures.
Always keep safelight exposure to a minimum. Store paper in
lighttight containers, and make a habit of handling paper with the
emulsion side down (away from the safelights). Place your enlarger
so that the easel area receives very little safelight illumination.
When you develop prints, insert the paper into the developer with
the emulsion side down; turn the paper emulsion side up when
experience tells you that the image has become visible. Let the
results of your safelight test and your own practical experience
guide you in determining how much time you have in handling
photographic materials.
TESTING YOUR SAFELIGHT CONDITIONS
Test for Black-and-White Papers
Before starting the test—
• Install a new bulb in each safelight housing, and verify that
you’ve selected the correct wattage for the paper you are
using.
• Inspect your darkroom for light leaks. Turn off the white lights.
If the room light is provided by fluorescent tubes, wait at least
5 minutes for the residual glow to dissipate. Then check to be
sure that no white light is entering the darkroom through
doorways, passthroughs, etc. (Remember, it takes at least 10
minutes for your eyes to become fully adjusted to the dark.)
• Correct any light leaks. Make sure that no white light is
escaping from the enlarger or safelight housings.
After you have prepared the darkroom, test your safelight
conditions by following the steps below:
1. Set up the enlarger. Insert the negative carrier with no negative
in it into the enlarger. Set up the easel with a mask to expose
an area as shown in Figure 1.
2. Turn the white lights off and turn the safelights on. Determine
which paper-handling area receives the brightest illumination.
This will usually be the area where you process prints.
3. Turn the safelights off, and run a test to determine what
enlarger
exposure is required to produce a light gray tone on
the photographic paper with standard processing. You will
probably have to set the lens to its smallest aperture and use a
very short exposure time. Place a sheet of the photographic
paper under the mask on the easel, and expose it. Process it in
total darkness. Compare the unexposed area to the exposed
area. The gray tone should have a reflection density of 0.25 to
0.50 (0.15 to 0.40 above the paper density) as measured with
a reflection densitometer. Or you can make a visual
comparison of the exposed area with the gray-scale steps in
KODAK Publication No. Q-16,
KODAK 24-Step Reflection
Density Guide
.
4. Make the first enlarger exposure.
All
the lights should be off.
For orientation, cut a corner from a fresh sheet of the
photographic paper, and position the paper under the mask
(see Figure 1). Expose the paper, using the time and aperture
you determined in step 3. Label this area “After” to indicate
safelight exposure that occurs
after
the enlarger exposure.
5. Make the safelight exposures. With all the lights still off, place
a large piece of cardboard on top of the developer tray or in the
area where safelight illumination is brightest. Place the
photographic paper on the cardboard. Using an opaque card,
cover about one fourth of the paper. Turn on the safelight, and
expose the uncovered part of the paper for 1 minute. Move the
card to cover half of the paper, and expose the other half for an
additional 2 minutes. Cover all but one fourth and expose it for
4 more minutes. The four parts of the paper will have received
0, 1, 3, and 7 minutes of safelight exposure. (See Figure 2.)