Wouldn't you be better off building a sensitometer setup using a (calibrated) step wedge?
I’m actually looking at modifying my setup a little bit to try to extract a bit more light out of it so I can get to at least zone 10, though I’d really like to expose up 7-8 stops over middle gray just to see what’s going on up there with replenished xtol. The slower films really tax my setup, but I think I need to make a couple modifications as I’ve got a handful of 80, and 25 speed films to work out development times for and right now I just don’t have enough light to make full 10+ zone exposures.
Wouldn't you be better off building a sensitometer setup using a (calibrated) step wedge?
Plotting can be done more easily with a pre-manufactured step tablet and contact exposure onto sheet film of the emulsion in question, and then densitometer reading the result. But that requires a true darkroom. Any stray light whatsoever ruins the accuracy of toe plotting, and acts like flashing above that. With films with high ASA sensitivity, or even slower films with a steep toe, even the luminous hands on an old fashioned darkroom timer on the other side of the room will skew the results and give you something misleading. To objectively plot and compare b&w films on the market today, you need accuracy, in ZS terms, all the way from 0 to around 12. That means plotting all the way from the fbf of the step tablet all 21 steps, which are .15 density (or half a stop) apart. That might take you beyond printable density, but does show you if and when the shoulder begins, along with other key aspects of the entire curve, and how different development regimens affect them. Don't laugh, 12 "zones" of light is not that rare in the high mtns, desert, or even out here in the redwoods when the sun is out. If Ansel Adams was Moses, he didn't quite get the job done with only 8 commandments or Zones. Pan F obeys only five of them. ... You could probably rig up a little black flocking removable booth between the enlarger lens mount and the baseboard, with sleeve opening cannibalized from a film tent, and do contact frame step tablets tests within that.
It's just so much easier using a pre-calibrated step tablet. To do it correctly using aperture changes, you'd need to actually test those settings using an easel densitometer - any expensive rare toy. I have one. The other problem with changing apertures is that you're changing the incidence of the light going from small to large apertures. That might not be a major issue if the lens is back off far enough and it's a relatively long lens relative to film size, but it might be an issue up close, which appears to be the case if you're trying to eek the most light out. But to whatever degree of accuracy you might want to take this project, a dark tent would be an asset. Just be careful with the material and keeping it a safe distance from anything hot like a colorhead. Or you could make a mini-darkroom just around the enlarger area using PVC pipe stands and buying a roll of high-quality black photographic velvet (not the paper-backed kind).
Not ideal in terms of lint issues; but I did my first exhibition based on a makeshift arrangement like that, and processed the sheet film in the furnace closet - not an ideal spot either!
Because I got bored, I quickly scaled both of Ilford's curves to match the plot Adrian has published and then shifted (very quickly and very roughly - I am not desperately inclined to spend hours cleaning off all of the artefacts of Ilford's graphs) the graph to line up with the b+f line. Pale grey is ID-11, darker is HC.
Discuss as you wish. The ID-11 curve checks out to G-Bar 0.62 pretty accurately I recall. Remember that in dealing with Ilford films, average gradient is what they design to, so these specific curve behaviours are likely there with good reason. Generally, if you get a result that significantly disagrees with the manufacturing data, you're more likely than the manufacturer to be making an error in your system of measurement
well, there you go.... the darker HC one looks to have the same shape as I’ve published. I’ll bet if you stuck them on top of each other there’d be shockingly close if not dead on.
Give or take the speed loss, yes.
Give or take the approx stop of speed loss, yes.There's still the question over why ID-11 produces such a significantly different curve above 1.0 density, but it may simply be down to specific developer exhaustion.
Ilford’s is relative log exposure. It doesn’t indicate what they actually exposed it at. I exposed mine at EI 50 and processed it to as close to G-bar 0.62 as I could reasonably get it.
also, looking a little closer, should the horizontal line on Ilford’s chart be at 1.0 instead of 0.9?
The time they state for the curve from HC is the same as they state for an EI of 50, but the speed rating test is carried out in ID-11. On that basis, how they match up to your results, and that HC-110 type developers are cited by Kodak as delivering a slower shadow speed than D-76, and that there's perhaps 1/3 stop difference between D-76 and Xtol in shadow speed, I'd suggest a stop slower shadow speed in HC compared to Xtol is probably a reasonable starting point for testing.
I think they go from absolute 0.0 rather than b+f. I shifted their curve up so that both your & their b+f's lined up - which was about 0.1 I think.
mmerig - you're totally wrong. Look at the length of the published curves in relation to each other. Practical testing confirms exactly what I stated, and it's been a known problem with PanF for decades. Even Ilford's marketing literature and description of these two respective films implies exactly the same thing. I've made hundreds of densitometer plots with FP4 (both old and new style), have shot and printed a great deal of it, especially 4x5 and 8x10 sheets, and have every legitimate reason to believe I understand these films far better than you do. I've got the two published curves right in front of me, right now, in their official tech sheets. You've stated all this backwards. It's Pan F that has the limitations of an S-curve, and FP4 the long straight line once it launches off the toe.
I did not have luck with PanF 50
Thanks Drew. This reply pretty much replicates your previous reply. What I was hoping you'd do is to show either what is wrong with the Ilford curves or show where on the curve the Pan F shoulder arrives. Has Ilford not shown enough in its graph for users to see that in a high contrast situation Pan F has limitations that FP4+ does not?Just go shoot some of each of these two respective films in a high contrast situation and then try to print texture in both the lowest and highest values. Then maybe you'll understand just how significantly different the characteristic curves truly are, even if unfamiliar with how these curves get plotted.
while FP4 behaves as having a moderate toe followed by a long straight section. These respective characteristics can be tweaked somewhat, but not really be fundamentally switched. ...HP5 has a substantially longer toe than FP4, but not an S-curve. It eventually shoulders off.
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