What is your experience with Pan F 50 Plus?

[DREW WILEY]

I don't have any experience with Ilfotec HC. Have more than enough developers in the lab already. If someone wants to induce a sag in the curve of FP4 to significantly extend the runway of the toe, and make this film reminiscent of old Plus X Pan sheet film, there are numerous ways to do that. I routinely it did for gently up-sweeping mask curves for Ciba printing instead of grubbing around looking for old stocks of Pan Masking Film, which was basically just Plus X minus the antihalation layer. But for color neg or dye transfer masking, I want a long low-contrast straight line instead, which requires a different set of dev tweaks; masks for black and white printing, different still. But one has to start with a film with a native long straight line curve to begin with, like FP4, or even better, TMX100. If a person tried that with PanF, it would be like a porcupine going into a hair salon and asking to walk out in soft curls.

 

[pentaxuser]

I'm not set up to post visual content right now. The same thing happens if a long densitometer plot is scrunched to fit a small graph, versus a short line stretched to fit the same space. It's not an apples to apples comparison.

So the answer is that Ilford for reasons known only to itself has scrunched up two long densitometer plots of for Pan F and FP4+ to fit a small graph and in so doing the FP4 graph exhibits the S curve but the Pan F graph scrunched the same way over presumably the same scale does not.

I can't really work out how scrunching up both curves over the same "long plot" results in the FP4+ curve demonstrating the S shape but not the Pan F?

If this is all making sense to others then please join in and say why two long densitometer plots scrunched into a much smaller graph results in two different graphs.

pentaxuser

 

[DREW WILEY]

I give up. Just go shoot some and see for yourself. Gosh knows how many prints I've made from each of these films, plus hundreds of densitometer plots of my own. I'll leave it to Ilford to explain the conspicuous change or perhaps accidental switch in their own graphs. But even a tomato changes shape if you step on it and compress it. In this case, a big tomato might have been forced to fit the same apparent space as just a slice of a smaller tomato. Don't know. Don't care. But I do know exactly what to expect from these two respective films, and can play either like a fiddle. But at this point, folks should do a little of their own homework. I already printed my share of exceptional FP4 prints today.

 

[pentaxuser]

Thanks Drew I think I can draw the conclusion that your view is that you know what the curves are in each film's case and having asserted this on numerous occasions that is all you feel obliged to do.

That's OK. You are not obliged to show us anything of course. Just a pity that you cannot show us the proof which apparently you are not set up to do as you stated in a previous post. Will you never have the set up to do so? This is a pity if this is the case as all you can do is then make statements of assertion on any subject. Some subjects of course can only be assertions( the Soapbox threads spring to mind but in one involving plotting graphs and on a subject which on the surface seems to result in a conclusion that is diametrically opposed to what the film maker itself seems to conclude on these two films, it is a pity that it has to be left that way.

So be it

pentaxuser

 

[mmerig]

So the answer is that Ilford for reasons known only to itself has scrunched up two long densitometer plots of for Pan F and FP4+ to fit a small graph and in so doing the FP4 graph exhibits the S curve but the Pan F graph scrunched the same way over presumably the same scale does not.

I can't really work out how scrunching up both curves over the same "long plot" results in the FP4+ curve demonstrating the S shape but not the Pan F?

If this is all making sense to others then please join in and say why two long densitometer plots scrunched into a much smaller graph results in two different graphs.

pentaxuser

As mentioned earlier in Post #115 , scaling is the same for the Ilford plots (i.e., the domain and range, as well as the units). The film developer was the same too. If Ilford's plots are not an apples-to apples comparison, nothing is. The curve shapes may change with another developer -- this would be an orange-to-orange comparison.

The relative lengths of the two axes (aspect ratio, or "scrunching") and the numeric range used in a graph have a strong influence on visual perception, and this was formally documented in 1914, but there was no consistent, rigorous way to do it. More recently, William Cleveland, at A T & T's Bell lab, came up with a mathematical approach that optimizes visual perception when rates of change are important (as with film response to light). For short, Cleveland calls it "banking to 45 degrees". Two key references are:

Cleveland, W. S., M. E. McGill, and R. McGill 1988. The shape parameter of a two-variable graph. Journal of the American Statistical Association 83:289-300

Cleveland, W. S. A model for studying display methods of statistical graphics (with discussion) 1993. Journal of Computational and Statistical Graphics 3:323-364.

The mathematics are complicated, and there is no closed solution, so an interative process is required. Fortunately, the shape parameter to be estimated is monotonic. Also, with a simple response curve like we are dealing with here, the solution is likewise simple and an eye-ball estimate is usually as good as the full-blown analysis. My own intuition, which has a fair amount of statistical training behind it, is that Ilford's graphs are close to the optimum and would show an S-curve for Pan-F if it was as strong as it was for FP4.

It would be interesting to see graphs of these two films with a more common developer, like ID-11.

My own experience with these two films is that neither is difficult to work with.

An effective approach could be to have a PHOTRIO thread containing density curves for various films and developer combinations. Of course emulsion type, developer, temperature, densitometer type, exposure target, etc. would need to go along with the graphs.

 

[DREW WILEY]

It doesn't help when the curves are published so small. But ID-11 graphs are available in the older tech sheets, which would replicate common D76 results too, but still be no substitute for a family of curves. Otherwise, I'm running out of patience with certain people who don't understand the basics. It's like reading music. It wouldn't matter if I posted a hundred plots if they don't know what the notes mean.

 

[mmerig]

It doesn't help when the curves are published so small. But ID-11 graphs are available in the older tech sheets, which would replicate common D76 results too, but still be no substitute for a family of curves. Otherwise, I'm running out of patience with certain people who don't understand the basics. It's like reading music. It wouldn't matter if I posted a hundred plots if they don't know what the notes mean.

The curves are 2 by 2.5 inches actual size on the page -- plenty large enough to see what is going on.

Helping people understand things is one of the purposes of the PHOTRIO website. If you have data contrary to Ilford's or have their old data sheets (as you implied), please post them.

Some people may not understand the plots, but why hold them back from everyone else who do understand them?

 

[warden]

As mentioned earlier in Post #115 , scaling is the same for the Ilford plots (i.e., the domain and range, as well as the units). The film developer was the same too. If Ilford's plots are not an apples-to apples comparison, nothing is. The curve shapes may change with another developer -- this would be an orange-to-orange comparison.

Thanks for your thoughts on this subject, and especially for sharing the curves from post #115 which are helpful. I see no reason whatsoever to doubt Ilford's characteristic curves for these films unless I see vetted evidence to the contrary and also Ilford's response to that evidence.

I use characteristic curves as an amateur mainly to decide which film would be best for low or high contrast settings and the curves are quite useful for that even if you don't go deep with the math behind it. If Ilford somehow got the curves for these two films reversed and didn't notice for years (?), or used incompetent testing procedures or whatever, well that would be a big problem of course, but I don't for a moment think that's happened and I will take the manufacturer's documentation on their product as the authority. They've earned that.

 

[DREW WILEY]

I don't have access to anything like a flatbed scanner. Left all that behind when I retired. Do all my own plots on official Kodak log paper. If anything represents a common denominator standard bridging multiple decades, that does. Tutorials and books are readily available. All the Kodak b&w film guides, often found in used bookstores, contain an introductory section explaining characteristic curves. A more involved paperback primer would be Sensitometry for Photographers by Eggleston. The problem with small graphs is that people do not ordinarily perceive the impact of what seems to them to be very minor differences, which in fact are significant because they are logarithmic, and would be more obvious on larger scale. That's particularly the case with toe profiles. The original Tech Sheets for current plus-version FP4 isn't even dated, but is based on ID11, ironically not even plotted to the point of the shoulder. But the distinction from Pan F is quite evident nonetheless. Pan F has a significantly longer toe, as well as a harsh shoulder beginning to be evident even in their kind of truncated presentation - in other words, an S curve, apples to apples. It takes quite a bit more exposure relative to rated speed for FP4 to shoulder off, though that characteristic would appear in a longer scale plot. A bigger graph would also allow one to subdivide sections into smaller increments and more easily detect what's really going on. With old fashioned plotting paper, you've got ten times as much grid detail.

 

[mmerig]

I don't have access to anything like a flatbed scanner. Left all that behind when I retired. Do all my own plots on official Kodak log paper. If anything represents a common denominator standard bridging multiple decades, that does. Tutorials and books are readily available. All the Kodak b&w film guides, often found in used bookstores, contain an introductory section explaining characteristic curves. A more involved paperback primer would be Sensitometry for Photographers by Eggleston. The problem with small graphs is that people do not ordinarily perceive the impact of what seems to them to be very minor differences, which in fact are significant because they are logarithmic, and would be more obvious on larger scale. That's particularly the case with toe profiles. The original Tech Sheets for current plus-version FP4 isn't even dated, but is based on ID11, ironically not even plotted to the point of the shoulder. But the distinction from Pan F is quite evident nonetheless. Pan F has a significantly longer toe, as well as a harsh shoulder beginning to be evident even in their kind of truncated presentation - in other words, an S curve, apples to apples. It takes quite a bit more exposure relative to rated speed for FP4 to shoulder off, though that characteristic would appear in a longer scale plot. A bigger graph would also allow one to subdivide sections into smaller increments and more easily detect what's really going on. With old fashioned plotting paper, you've got ten times as much grid detail.

In post # 60 of this thread, you say: " I'm no expert at it - the only digital SLR I own is strictly for copystand work in the lab, where the lighting is tightly controlled"

Why not take a picture of your graph? I think some of us would like to see official Kodak graph paper, and compare it to ordinary graph paper, made by say Keuffel and Esser. Any plotted data on it would be a bonus.

Given all of the technical advice you give, I think you can manage getting a jpg file from your camera onto the internet.

 

[DREW WILEY]

Yes, I understand. I'm not allowed to use this computer for visual content. My wife needs it for work. My old Mac is disconnected, and I'd want to update any visual software anyway. One step at a time. The copystand is calibrated, but I have much more important priorities than web content at the point in time. If this topic warranted the fuss, which it doesn't, there are other hypothetical options; but even the local library is closed due to the virus. Plenty of people are familiar with the working characteristics of these specific films, whether they've studied the specific sensitometry or not; and everything I've stated can be verified in practical experience.