Tabular: terrific or terrible? Your opinions, please.

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And, for the sake of completeness, here are the curves for the P3200 and Delta 3200.

Ilford Delta 3200:


My own in D-76. Notice a different shape of the curve family:


Kodak P3200:


And my own P3200 in D-76. I will add that the curves in D-76 were lumpy, but they were nicely well-formed in XTOL and XTOL-R.
[
 

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Thank you @aparat. Going back to Fomapan 100 and 200 - they seem to reach ISO 100 and 125 respectively?
 
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Thank you @aparat. Going back to Fomapan 100 and 200 - they seem to reach ISO 100 and 125 respectively?

You're welcome. Yes, in my tests, they do. They may respond slightly differently to different developers. It's something that needs to be investigated further.
 

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The preference for grain is at least partially explained by our affinity for the perception of "sharpness". "Sharpness" is as much subjective as objective, and relates most closely to our ability to perceive edges of detail. If there is little or no grain, it is more difficult to perceive edges. Film with more grain can't resolve as much detail as film with less grain, but the additional grain can make things look more pleasing.
The Anchell and Troop complaints about the T-Max films strike me as entertaining, because the things they (or perhaps just Anchell) complain about are essentially the same things that one observes if one just uses larger film formats.

I have read that Crawley believed that the grain of Tmax 100 was so fine that its lack of prominent edges made it look less sharp. I don't know if that has been proved, but it is a reminder of the distinction between the physical characteristics of photo materials and how they may be perceived. Crawley formulated his FX-37 and FX-39 developers to address the problems he saw with tab grain films, though they can be used with other films. The TMX and TMY neg's using FX-37 were some of the cleanest and crispest I have seen on a light table. There is prominent grain with FX-37. But the acutance is stellar in my estimation and they they are speed increasing developers, unlike some other high acutance developers.
 
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I’m intrigued to know what chemical explanation there can be for lumpy curves?
Me too. So far, the most lumpy curves I have ever come across were the KODAK T-MAX P3200 in D-76. As you can see above (#201), the curves supplied by Kodak are equally lumpy. Perhaps it is the cost of the improvement in film speed? It would be nice to hear from Kodak. I am sure they know.
 
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I have a minor update to this thread. I finished plotting Ilford Delta 100 in stock XTOL. I have tested Delta a lot because I really like this film. It just works for me. The curves are similar in XTOL and XTOL-R, except for a slight drop in film speed (ISO 100 in XTOL and ISO 84 in XTOL-R), and the difference in development time. Overall, both developers produce fantastic results with this film. In my book, it's as good a pairing as it gets.

delta100_XTOL by Nick Mazur, on Flickr

delta100 by Nick Mazur, on Flickr
 

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I remember clearly, I was listening to NPR (National Public Radio USA) when there was a story about a breakthrough that Eastman Kodak had that allowed for fast film with dramatically improved grain and sharpness. TMax films and VR color films were what they were talking about.
I've been a TMY/TMY-2/TMY user ever since TMX too. Portra 160 and 400.

All Ilford for sheet film and a lot of rolls FP4 Plus is awesome as are everything Ilford makes.
 

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I have a minor update to this thread. I finished plotting Ilford Delta 100 in stock XTOL. I have tested Delta a lot because I really like this film. It just works for me. The curves are similar in XTOL and XTOL-R, except for a slight drop in film speed (ISO 100 in XTOL and ISO 84 in XTOL-R), and the difference in development time. Overall, both developers produce fantastic results with this film. In my book, it's as good a pairing as it gets.

delta100_XTOL by Nick Mazur, on Flickr

delta100 by Nick Mazur, on Flickr

Hello Nick, the time for the green line in stock Xtol seems to be wrong.
 
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Hello Nick, the time for the green line in stock Xtol seems to be wrong.
Indeed! Thank you for pointing it out. I fixed it:

delta100_XTOL by Nick Mazur, on Flickr

And here's the summary table:
delta100XTOLTable.png
 
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Therefore, it would be great if you all could share your more recent experiences with these films, and, in particular, tell us your preferences for different types of photography and different types of workflow.

Back In The Day, I primarily shot T-Max because it was the latest-and-greatest, smallest-grain stuff. Now that I'm back to photography, I prefer traditional grain films. T-Max still does what it does, but to me, what it does can be done better with digital. It just doesn't have the character I like. Now, all that said, I might try it in medium format, where that low-grain almost-digital look could be cool. For now, though, it's primarily FP4, HP5 and Kentmere for me.

Aaron
 

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What digital CAN'T do, TMax can. Where do all you guy come up with all this, "looks like digital" nonsense? If you want a little more edge acutance or "tooth" effect, shoot TMY400 instead of TMX100. I shoot em both in 35mm, 6X7, 6X9, 4X5, and 8X10, and not a single print I've ever enlarged from any of the above (and there have been hundreds of em) resembled anything digital, thank goodness!
Just keep one digit on the shutter or cable release button, and save the rest of your fingers for tossing your electronic camera in the nearest lake, and you'll be fine.
 

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For 8 min dev time (and a few other cases), gamma is lower than G or CI. Seems counter intuitive since G or CI include part of the toe.
1675497192957.png

delta100XTOLTable.png
Can you please comment. Even better mark on the 8-min D-logE curve the segments actually used to derive gamma, G, CI.
Thank you.
 

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Where do all you guy come up with all this, "looks like digital" nonsense?

I use this film in 4x5 and I don't have near the experience that you have with it but these observations on TMX I find are somewhat of a head scratcher myself. It's odd opinion........imo, 🙂. To each their own.
 
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For 8 min dev time (and a few other cases), gamma is lower than G or CI. Seems counter intuitive since G or CI include part of the toe.
View attachment 328651
delta100XTOLTable.png
Can you please comment. Even better mark on the 8-min D-logE curve the segments actually used to derive gamma, G, CI.
Thank you.
That's a great observation! Thank you for bringing it up. Gamma is a parameter that does not always fit the characteristic curve well. It relies on identifying the "straight-line" portion of the curve. Back in the 1940s and 1950s when the research into film was at its peak, the mathematical model of the film curve assumed the existence of the toe and clearly-defined straight-line portion of the curve (and a shoulder, if needed). With such curves, Gamma works very well. It's easy to unambiguously identify the portion of the curve. However, with more complex curves, especially those with significant curvature in the midtones, the statistically derived straight-line portion of the curve may not always correspond to what, typically, the photographer would identify as such. There's an interesting discussion of that issue in this thread. I hope this helps.

So, to sum up, because of the problematic nature of Gamma, other measures of the slope were created, with the Contrast Index and Average Gradient being the two most dominant models over the years. And finally, my program computes Gamma by identifying the straight-line portion of the curve statistically, so it may not always be the best "fit" for the photographer. That's why the Contrast Index and Average Gradient are probably more useful in this type of analysis.
 

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Well, digital does have all those instant "app" features ... press a button and you can get the same looks as cobwebs or fungus inside the lens; press another and everything looks like cracked pottery; yet another, and it simulates a broad-brushed Impressionistic painting. So I guess if they came up with an app which makes the result look identical to 4X5 or 8X10 TMax film, well, that would be something. But don't hold your breath.

And size matters. Saw a compelling image in a digi camera article a few days ago that did indeed look nice on the screen. But go figure : it was a crop of a crop of a crop from a full-frame 35mm DLSR, at that point amounting to about a quarter square inch of actual light capture surface. That's 1/320th the size of 8x10 film, or 1/80th of 4X5. So let's make a real print of that itty bitty little pixel rodent and hang it on a wall, instead of on the web, and see how the they compare!

TMax films are highly amenable to various developers and degrees of development. Grain structure and edge acutance itself can be modified that way. It has its own full suite of chemical "apps". So I don't seen how any of this generic talk about this or that "look" makes any sense at all. Sure, there are lots of good film choices out there. But it takes awhile to really learn the suite of personality options to any of them. Serious printing experience with them is needed too.
 

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Well, digital does have all those instant "app" features ... press a button and you can get the same looks as cobwebs or fungus inside the lens; press another and everything looks like cracked pottery; yet another, and it simulates a broad-brushed Impressionistic painting. So I guess if they came up with an app which makes the result look identical to 4X5 or 8X10 TMax film, well, that would be something. But don't hold your breath.

And size matters. Saw a compelling image in a digi camera article a few days ago that did indeed look nice on the screen. But go figure : it was a crop of a crop of a crop from a full-frame 35mm DLSR, at that point amounting to about a quarter square inch of actual light capture surface. That's 1/320th the size of 8x10 film, or 1/80th of 4X5. So let's make a real print of that itty bitty little pixel rodent and hang it on a wall, instead of on the web, and see how the they compare!

TMax films are highly amenable to various developers and degrees of development. Grain structure and edge acutance itself can be modified that way. It has its own full suite of chemical "apps". So I don't seen how any of this generic talk about this or that "look" makes any sense at all. Sure, there are lots of good film choices out there. But it takes awhile to really learn the suite of personality options to any of them. Serious printing experience with them is needed too.

Would you be kind enough to provide a link to the digital image you are commenting on?
 

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@aparat I suspect the maximum value of the derivative of the function that describes the characteristic curve is a very good approximation of gamma. I can only see it fail if the film doesn't shoulder at all and has an upswept curve at the highlights. Perhaps disregarding that area can take care of this.
 
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What digital CAN'T do, TMax can. Where do all you guy come up with all this, "looks like digital" nonsense? If you want a little more edge acutance or "tooth" effect, shoot TMY400 instead of TMX100. I shoot em both in 35mm, 6X7, 6X9, 4X5, and 8X10, and not a single print I've ever enlarged from any of the above (and there have been hundreds of em) resembled anything digital, thank goodness!
Just keep one digit on the shutter or cable release button, and save the rest of your fingers for tossing your electronic camera in the nearest lake, and you'll be fine.

What is that?
 

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(...snip...)Gamma is a parameter that does not always fit the characteristic curve well. It relies on identifying the "straight-line" portion of the curve. Back in the 1940s and 1950s when the research into film was at its peak, the mathematical model of the film curve assumed the existence of the toe and clearly-defined straight-line portion of the curve (and a shoulder, if needed). With such curves, Gamma works very well. It's easy to unambiguously identify the portion of the curve. However, with more complex curves, especially those with significant curvature in the midtones, the statistically derived straight-line portion of the curve may not always correspond to what, typically, the photographer would identify as such. There's an interesting discussion of that issue in this thread. I hope this helps.

(...snip...) And finally, my program computes Gamma by identifying the straight-line portion of the curve statistically, so it may not always be the best "fit" for the photographer. That's why the Contrast Index and Average Gradient are probably more useful in this type of analysis.
@aparat,
I have digitized (with suitable freeware) your curve for Delta100 in Xtol 8min, as shown in your post #210 above. Using basic software LibreOffice Calc) I have plotted
  • all digitized points : small blue dots
  • points selected by me as representative of the "straight-line portion"; choice did not seem critical or problematic
  • a least-squares fit of a linear relation to the above-mentioned "straight-line portion", and the corresponding equation
GammaFit.png

Rounding up by 0.002, the gamma results as 0.70. Not 0.56. And identifying the straight-line portion is not problematic, as one can see at a glance from the near-perfect agreement between the fit line and the red crosses.

I don't know what is (what might be) a statistically derived value of gamma, when there is one data set to work with.

A separate point. In my opinion, CI and G-bar were not created because the straight-line portion of the D-logE curve was difficult to identify. But rather because in actual use for pictorial photography, the scene values are not generally placed entirely in the straight-line portion (except maybe for reproduction work). But rather with some shadow values in the toe; so that for the purpose of translating scene brightness range to density range, CI or G-bar are more useful.

Might sound like I'm nagging at your valuable work. Not so. You have provided lots of excellent and useful data. My remarks aim to help you correct what I perceive as errors.
 
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bernard_L

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@aparat I suspect the maximum value of the derivative of the function that describes the characteristic curve is a very good approximation of gamma. I can only see it fail if the film doesn't shoulder at all and has an upswept curve at the highlights. Perhaps disregarding that area can take care of this.
Obtaining the derivative of a function defined by experimental data is tricky, because differentiation amplifies measurement noise. To avoid this one must replace the actual data by a model with suitable "smoothness". See e.g. https://www.photrio.com/forum/threads/comparing-paper-characteristic-curves.171700/post-2235872
But this is a tricky business; if one is not careful, soon one is discussing properties of the chosen model, having nothing to do with the data and he real world.
 

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@bernard_L Ah, yes, I see your point. Maximum value can be influenced by a slightly lower value of the initial data. That would cause a higher derivative value.
 

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@bernard_L Ah, yes, I see your point. Maximum value can be influenced by a slightly lower value of the initial data. That would cause a higher derivative value.
Visualize a saw blade held horizontally. The global slope is small or zero. The saw tooths are small deviations from the general slope. Yet the local slope (derivative) alternates between +/-60 degrees. Going from a wood saw to a metal saw, the teeth are smaller, so the height deviation from the mean line is smaller, but the excursion of then derivative remains as large. That is what meant when I wrote that taking the derivative amplifies noise. Of course there is a more formal and rigorous derivation of that statement, but here is not the place for that.
 
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