Testing Your Safelight Conditions
Before starting the test--
After you have prepared the darkroom, test your safelight conditions by following the steps below:
Safelight Test Procedure for Black-and-White Papers
Test A in Evaluation of Safelight Test for Black-and-White Papers shows no added density on either side of the paper as a result of safelight exposure. This condition represents a safe time of at least 7 minutes.
Test B in Evaluation of Safelight Test for Black-and-White Papers shows a potentially unsafe condition. The part of the paper that received a 7 minute exposure to the safelight alone is fogged. (Compare the density shown in the bottom fourth of the paper to the center and the borders of the rest of the paper.) The paper also shows signs of image change starting at 1 minute in the "Before" area, and at 3 minutes in the "After" area. This means that you must handle the paper very carefully before and after the enlarger exposure. If your safelight filter is old, results like these could indicate filter fading; replacing the filter should give you a longer safe time. If the filter is new, you can extend the safe time by using a lower-wattage bulb; moving the safelight lamp to a greater distance; using only dim, indirect safelighting for handling; or developing the paper for half the total time with the safelight off. Of course, you could avoid the risk of fogging if you develop the paper without any safelight illumination, or adhere strictly to the safe time indicated by the test.
A more typical result is shown in Test C in Evaluation of Safelight Test for Black-and-White Papers. The paper is safe for up to 7 minutes of safelight exposure before the enlarger exposure, and up to 3 minutes of safelight exposure after the enlarger exposure. The test indicates that conditions are safe if you limit the total safelight exposure time to 3 minutes.
Some products are more sensitive to one sequence of exposures than to another. You can compare products by using this test or variations of it.
Blue-sensitive and orthochromatic sheet films are sometimes loaded into holders and processed in trays under safelights. You can devise a test for determining a safe time for these materials that is similar to the "Test for Black-and-White Papers." However, instead of exposing the film with an enlarger to provide the gray-tone exposure, expose the film in a camera.
Make a test object by mounting a KODAK Gray Card (KODAK Publication No. R-27) vertically on a jet-black, non-reflective background. Take a meter reading of the test object (including the black borders around the gray card). Then set the camera aperture and shutter speed to give about 1 stop less exposure than the meter indicates. You are now ready to expose two separate sheets of film.
Load two sheets of film into a film holder in total darkness. Make a camera exposure of the test object with the first sheet of film. Label this film "After" because safelight exposure will occur after camera exposure. Next, expose sections of the sheet of film to the safelight where you process the film. This is similar to the test for paper, except that you should try a total of 0, 4, 7, and 13 minutes, respectively. One quarter of the sheet receives no exposure. The next quarter receives 4 minutes. A third quarter receives 7 minutes (4 minutes + 3 minutes). The last quarter receives 13 minutes (4 minutes + 3 minutes + 6 minutes).
Then take the second sheet of film and expose sections of it to the safelight where you load film into holders. Use the same safelight exposure times that you used for the first sheet. Then make a camera exposure of the test object, using the same aperture and shutter speed as for the first sheet of film. Label it "Before."
Process both sheets of film in total darkness. After normal processing, a continuous-tone film should have a transmission density of approximately 0.4 in the gray-card area. The black border surrounding the gray card should not differ appreciably in density form the gross fog level of the film.* If the density of the gray-card area exceeds 0.4, or the density of the black border is much greater than the gross fog level, safelight fog may have occurred. You can evaluate your results by comparing them to the conditions described in step 8 under "Test for Black-and-White Papers."
Evaluation of Safelight Tests for Black-and White Papers
You can also adapt this test for use with papers in rolls. Roll papers that are printed in automatic or semiautomatic printers are susceptible to safelight exposure when you load and unload the printer, and when you load the paper into a processor. Adapt the safelight test to these operations by carefully studying your paper-handling procedures.
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