Making a Test Strip
Properly executed test strips are the key to good prints. Test strips are used to determine exposure time, contrast adjustments, and processing time. The methods here are not using polycontrast filters- see split-filter printing- but are the same methods used with filters, or with graded papers. Probably the single most important part of testing is to strictly follow processing times. The tendency is to rush through processing test strips (or test prints), but this will only get you inconsistent (read: useless) results. Processing is half the equation here.
There are two ways of creating a test strip- mathematical and geometrical. The first procedure outlined will be the mathematical, which adds exposure by even increments of time.
Needed:
- Photo paper
- Negatives
- Tape
- Board
A regular test print.
Mathematical (Normal)
- Start by putting the negative in the enlarger, get it focused, get it sized, and stop the enlarger down to ƒ8 or ƒ11. You want an aperture that's somewhere in the middle. The size of your enlargements, and the general density of your negatives will determine exactly what aperture you start at. Smaller enlargemennts will usually take a smaller aperture, and denser negatives will usually require a larger aperture. Regardless, the first test will show you.
- Cut a piece of paper into strips. I usually use 4 x 5" pieces, just quartering an 8 x 10 sheet. If you want to use actual strips, cut the paper into quarters lengthwise. The idea here is to use a piece of paper big enough to tell you something. Little strips torn off a corner don't even make good bookmarks.
- Place the strip on the printing easel, emulsion side up, in an important area that (hopefully) has both dark shadows and highlight areas. If there doesn't seem to be a good area with both, choose an important shadow. (We'll establish the shadows first, and adjust for highlights later).
- Tape the strip down, with a small piece of masking tape. This will, hopefully, keep you from moving the strip while you are doing the test.
- Set your timer for 2 seconds. This will allow adjustment, if needed.
- Cover about 4/5ths of the paper with your board. Make sure you use opaque board- not another piece of photo paper! You need to completely mask the light. Also, orient the board so that the dark and light areas will be on each strip.
- Pop the timer to make a 2-second exposure.
- Move the board down (or over) a fifth, and make another exposure. This will give you a strip of 4 seconds (the first exposure plus the second) and a strip of 2 seconds.
- Repeat step 8, moving your board down another 1/5th, making another 2-second exposure. Get the drift? Keep going until you run out of paper.
- Process the paper. Make sure and do everything for the full amount of time. It may be boring, but if you skimp or rush, the results will not be accurate. It will be a waste of time and money.
- Take the strip out of the darkroom, and view it in good light. Ideally, one of the exposures will be correct— it will show details in both the shadows and the highlights. More often, some contrast adjustments will need to be made. You do that by using the split-filter or split-contrast method.
- IF you were lucky enough to get a solid result, go ahead and make a test print, on a full piece of paper. Do exactly what you did before. If you determined, in step 11, that the ideal exposure was 8 seconds, then expose the print for 4 2-second intervals. This repeats the test, and with a repeating timer, will eliminate any small errors from the timer. It also removes what is called the intermittancy factor— which, briefly put, is a physics thing which states that 4 2-seconds shots of light is NOT the same as 1 8-second shot.
- Process the paper. Again, try and do everything the same. Consistency counts. This full print will tell you more than the test strip, and should guide you in adjusting and refining contrast and exposure.
- If the test is really light overall, you may want to try the geometric method.
