Fstop timing

[flamberge]

You can easily get into really long exposure times with f-stop timing. For example if you need to increase a one-second exposure by 60 stops, your exposure will be longer than the estimated history of the universe.

log2(436117076600000000) = 58

Hi

I said in my previous post the increase in densitiy with longer exposures is "within limits". The point is, it doesn't matter if you mesure in seconds or f-stops. There will be some point in exposure time where you get the maximum density the paper is capable to achieve. There will be no more silver in the paper to be converted. After that, any longer exposure time is a waste of time.

And IMHO for getting maximum densities, at least with current chemistry and available photo papers, the amout of time involved I think is a little shorter than the estimated history of the universe.

kind regards

[Maris Rusis]

Back when I printed for others speed of production and efficient use of paper was the key to productivity and $. And f-stop timing was never part of it - too slow.

Because of always working in the same darkroom with the same enlarger and the same paper easel I could just look at the projected image and have a very good idea of the required print exposure. This came easily after only a few hundred expose, develop, fix, and look cycles. Doesn't this happen to other people?

An example: If I figure the print exposure is about 8 seconds I'll line up a long test strip that samples the thinnest and densest part of the projected negative together with a selection of mid-tones. Then with my foot-switch activated timer set to 2 seconds I make exposures 2-4-6-8-10-12-14 seconds. The test strip will be too light at one end and too dark at the other end so the correct exposure must lie between. Because I sampled thin and dense parts of the negative I also have information about possible burning and dodging. Suppose the correct exposure is 9 seconds I'll tap the foot-switch 4 times to get to 8 seconds then close the lens 1 stop and tap the foot-switch one more time to get to 9 seconds. Aha, f-stops do get involved!

[Vaughn]

Makes sense, Maris. There's a bit of art (or at least common sense) that goes into a proper test strip...which for me means big enough to be useful, and placed where one gets the most useful information about the whole image.

I made a full size work print from the results of the test strip. It did not have to be right-on. I could study it, make any minor changes in exposure and start making decisions for how to work with the image (mostly burning).

[jnantz]

I 've found just closing fstop down 3 clicks and doing a test strip, and if I am doing multiple prints from exposures that all around the same density, &c, I've been fortunate enough to know how to guesstimate the exposure pretty well ... for me at least test strips are not too hard and just easy enough for me to screw it up from time to time.

[flamberge]

Suppose the correct exposure is 9 seconds I'll tap the foot-switch 4 times to get to 8 seconds then close the lens 1 stop and tap the foot-switch one more time to get to 9 seconds. Aha, f-stops do get involved!

Indeed, that's the other way of using the f-stop method. In fact, it's the real one. The problem is, most enlarging lenses have AFAIK full or at most 1/2 f-stops increments.

Using seconds allows you to choose full, 1/2, 1/3, 1/4 (or whatever) f-stops progressions. Better fine tuning.

[Doremus Scudder]

The whole point of moving away from a test strip made in equal intervals is to avoid the unevenness of exposure in the sequence of stripes. With a set time increment, that the amount of density change with each subsequent stripe progressively decreases. If you make a test strip in two-second intervals, the second stripe will be twice the original exposure, the third will be only about 1.5 times the previous exposure, the fourth only 1.25 times the previous exposure, and so forth.

This makes the actual exposure difference between stripes uneven and makes telling them apart at the far end of the scale rather difficult (I remember strips where I couldn't fine the "line" between exposures; simply too close together).

While I agree that f-stop timing is too fiddly, both f-stop timing or using percentages (as I do) fixes this problem. I prefer percentages because it is faster and more even than both f-stop timing and just using even increments to make a test strip.

But the usefulness doesn't stop there. Recording burning, dodging and split-grade exposures in percentages of a base exposure really help when making a different-size print or a print on different paper with a different speed. Once the base exposure is found for the new print, one can get very close to the right manipulations by just re-calculating their times from the base exposure using the percentages. Again - faster.

All the methods work; it's just a matter of streamlining things and using what seems most intuitive and practical for you.

Best,

Doremus