lf_dean
5-May-2023, 17:55
I just finished developing my three sheets of Delta 100 in D76 1:1, as per the "Your Personal Reference Speed Point" article on BTZS.org, and the tip of the ISO triangle falls right at 2.25 on the X-axis. The exposure was setup exactly as described in the article, EV 4.0 as metered off a white card in the center of the light circle, digital timer set for 0.5s. And the 4, 8 and 16min curves come in with EFS 40+, 64+ and 80 for SBRs of 8.3, 5.8, and 3.7 respectively with the Plotter default PSP of 2.4.
According to the article, what I *should* do is increase the exposure by a half-stop to EV 4.5 so that the tip of the ISO triangle will land right at 2.4 (or set my PSP to 2.25), which will give the three curves EFS of 64--, 100--, and 100+. Then use that as the reference exposure for all future film tests. But that feels like fudging the data to match expectations, not following the data to its logical conclusion.
Assuming my meter is metering accurately and I'm really getting EV 4.0 worth of light out of the enlarger. And, assuming my timer is working correctly and really giving me 0.5s. Shouldn't I conclude that my workflow is yielding the lower film speeds rather than trying to fudge the test exposure to give me what the box says? Even if my meter isn't reading correctly, it's the meter I'm using out in the world, so it should be off by a consistent amount out there too...
Or, given that it's only half a stop and some of my shutters probably have at least that much slop in them, am I over thinking this? Should I just pick one, go point the camera at stuff, and make photographs?
Dean
Oh, btw. Not actually brand new at this, it's just been 20 years some of those brain cells are pretty dusty...
According to the article, what I *should* do is increase the exposure by a half-stop to EV 4.5 so that the tip of the ISO triangle will land right at 2.4 (or set my PSP to 2.25), which will give the three curves EFS of 64--, 100--, and 100+. Then use that as the reference exposure for all future film tests. But that feels like fudging the data to match expectations, not following the data to its logical conclusion.
Assuming my meter is metering accurately and I'm really getting EV 4.0 worth of light out of the enlarger. And, assuming my timer is working correctly and really giving me 0.5s. Shouldn't I conclude that my workflow is yielding the lower film speeds rather than trying to fudge the test exposure to give me what the box says? Even if my meter isn't reading correctly, it's the meter I'm using out in the world, so it should be off by a consistent amount out there too...
Or, given that it's only half a stop and some of my shutters probably have at least that much slop in them, am I over thinking this? Should I just pick one, go point the camera at stuff, and make photographs?
Dean
Oh, btw. Not actually brand new at this, it's just been 20 years some of those brain cells are pretty dusty...