• OK Thomas, now you have me confused. It sounds like you are recommending this sequence:

Paper uncovered
1st exposure = 32 seconds
Cover a bit of paper and give 22 seconds more (that strip would now have a total of 54 seconds).
Cover a bit of paper and give 16 seconds more (that strip would now have a total of 70 seconds).
Cover a bit of paper and give 11 seconds more (that strip would now have a total of 81 seconds).
Cover a bit of paper and give 8 seconds more (that strip would now have a total of 89 seconds).
Cover a bit of paper and give 5.6 seconds more (that strip would now have a total of 94.6 seconds).
Cover a bit of paper and give 4 seconds more (that strip would now have a total of 98.6 seconds).

Those are huge times! Or do you mean:

Paper uncovered
Expose for 4 seconds
Cover a bit of paper and give 5.6 seconds more (that strip would now have a total of 9.6 seconds).
Cover a bit of paper and give 8 seconds more (that strip would now have a total of 17.6 seconds).
Cover a bit of paper and give 11 seconds more (that strip would now have a total of 28.6 seconds).
Cover a bit of paper and give 16 seconds more (that strip would now have a total of 44.6 seconds).
Cover a bit of paper and give 22 seconds more (that strip would now have a total of 64.6 seconds).
Cover a bit of paper and give 32 seconds more (that strip would now have a total of 96.6 seconds).

Either way it makes no sense to me. What am I missing?

In a previous thread I recommended:

Paper uncovered
Give an exposure of 8 seconds
Cover a bit of paper and give 2 seconds more (that strip would now have a total of 10 seconds which is one-third stop more than the previous strip has).
Cover a bit of paper and give 2.5 seconds more (that strip would now have a total of 12.5 seconds which is one-third stop more than the previous strip has).
Cover a bit of paper and give 3.5 seconds more (that strip would now have a total of 16 seconds which is one-third stop more than the previous strip has and one full stop more than the first strip).
Cover a bit of paper and give 4 seconds more (that strip would now have a total of 20 seconds which is one-third stop more than the previous strip has).
Cover a bit of paper and give 5 seconds more (that strip would now have a total of 25 seconds which is one-third stop more than the previous strip has).
Cover a bit of paper and give 7 seconds more (that strip would now have a total of 32 seconds which is one-third stop more than the previous strip has and two full stops more than the first strip).
Cover a bit of paper and give 8 seconds more (that strip would now have a total of 40 seconds which is one-third stop more than the previous strip has).
Cover a bit of paper and give 10 seconds more (that strip would now have a total of 50 seconds which is one-third stop more than the previous strip has).
Cover a bit of paper and give 14 seconds more (that strip would now have a total of 64 seconds which is one-third stop more than the previous strip has and three full stops more than the first strip).

This sequence above increases in 1/3-stop geometric intervals and each strip is very distinct and appears visually to be the same amount of increase between each step. Conversely, an arithmetic sequence with an interval of 5-seconds becomes less and less effective as the total time increases. From 5 seconds to 10 seconds, the 5-second interval represents 100% change in exposure (or one full f/stop) but from 45 seconds to 50 seconds is only about a 10% increase.

If you examine the sequence I use, you will notice that it increases the same as film speeds: ISO 8 (Efke 820 Infrared w/cutoff filter), ISO 10, ISO 12, ISO 16, ISO 20, ISO 25 (as in Kodachrome 25), ISO 32 (Polaroid type 55 negative) ISO 40 (Kodachrome A), ISO 50 (Efke 50), ISO 64 (Kodachrome 64), ISO 80 (Ilford Ortho Plus), ISO 100 (T-Max 100), ISO 125 (Plus-X), ISO 160 (High Speed Ektachrome), ISO 200 (Kodak Gold 200), ISO 250, ISO 320 (Tri-X Professional TXP), ISO 400 (TMAX 400), etc. Each subsequent strip is a true geometric increase of 1/3-stop just like the ISO film speed sequence.

Just write the test strip exposure sequence down and keep it next to your enlarger. That way you won't have to memorize the sequence and you will have much improved test strips.

Joe

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Originally Posted by Thomas Bertilsson
Make sure that the material you use to cover your paper with when making the test strip is entirely opaque. Or some light will shine through and fog the paper underneath.

Also, instead of doing 5 second increments, I recommend using the values on the f/stop ring on your camera lens. 32s, 22s, 16s, 11s, 8s, 5.6s, and 4s. You go backwards like that, so that the first strip is 32 seconds, next is 22 seconds, etc. It gives you one full stop between strips and gives you a better idea of what different levels of exposure will do in your final print.

Good luck. Keep posting back here with your results.