Hi film community,
After building my scanning rig and shooting and scanning many rolls of B&W, I am still optimizing film stock and development, and after wanting to try the Zone System, I took some months to understand how this could be made to work in our digital scanning environments.
In this exercise, I developed a procedure to obtain a full H-D (density versus log(exposure)) curve for a B&W film using one frame only. This is possible both using scanning and PS, and obviously similarly using a classic densitometer, but still obtaining the full curve with only one frame.
I believe it could be useful for those still shooting (and scanning) B&W film and therefore wanted to share my findings here, which are summarize in one of my blog pages:
Thanks for the link, Arno.
Tried to read the page…but it’s too long and detailed for my taste.
Can you add a management summary on top of the text?
1 or 2 paragraphs, readable without scrolling
Very interesting work, it will take me a while to digest that. It would be interesting to see some conversion comparisons with and without your linear profile approach.
Thanks for the article, @ArnoG!
Just to clarify re: profiles, the camera profiles already included with Negative Lab Pro are already linear and make additional corrections beyond the approach mentioned the article (i.e. using the DNG Profile Editor and changing the tone profile to “linear”).
Even if you set the tone profile to “linear” in the DNG Profile Editor, there are still a number of things you would need to do to get the optimal negative conversion profiles… for instance: 1) correcting for “highlight” rolloff (to match the actual highlight data, as was done prior to PV2012, 2) removing any “hue twists” from the profile (this will matter more for color negatives than black and white), 3) Removing any black point compensation (which will impact toning in the highlights once the negative is inverted), 4) adding protection for gamut to make sure the inverted colors stays in the right color space…
All that is already being done in the Negative Lab Pro camera profiles, which you are free to use even if you are inverting manually!
I would also suggest that histograms and tone curves are the digital replacement for the Zone System.
Thanks for the feedback and suggestions.
The reason I invested quite some time to write it down is since I believe it’s an entirely new approach to obtain full H-D curves from one shot using a suitable adaption of the zone system for our current digital environment. It’s a very powerful method to obtain in one frame the film’s tonal response, especially for quickly comparing film A with film B. I’m even contemplating whether I should submit it to some scientific photography journal, but that would take another blob of time in which I’m not exactly swimming, so having it available online should suffice for now.
@Digitizer : I did add a short version on top, that is very short in text but the tables and graph make it seem longer. I couldn’t really compress it further since I need to sketch the issues shortly and then the solution, but it should be very accessible now, with a longer version below for those who want to understand the details.
@nate : Yes, I am aware. We had this discussion on a custom linear profile before where you mentioned there were more issues than just linearity of the profile, which is indeed entirely correct. What frustrated me somewhat is that Adobe seems to make changes from process version to process version that don’t seem to be documented, and also that in my case I couldn’t exactly reproduce what others over at Rawdigger had found to obtain tonal accuracy using a zeroed out PV2. This still puzzles me. I suppose that you are keeping track of what Adobe is doing in order to maintain your linear-overall NLP profile so I would be perfectly happy relying on that profile. As far as I could tell, my custom version and your NLP version seem both to retain linearity but I might be missing more hidden Adobe things that you are obviously aware off. In the short version I did add the suggestion to use the NLP profile, so folks can use that instead.
@Col : I did include a comparison to Adobe’s Monochrome profile, which is non-linear and adds visibly an s-curve to the conversion. This kills tonal accuracy, but is likely done to provide punch to a B&W converted digital color photo by adding more contrast.
This is what happens when you allow ChatGPT to play unsupervised.
This is brilliant! From my point of view this methodology can be applied to the camera scanning backing light. Just few days ago I took the reading of one popular lightsource and found out that the center is at least 1 stop brighter than corners if one uses RawDigger to read the raw file. So I started tinkering with numbers to calculate what mask at with density as function of x and y should be printed to make source uniform to better degree. I actually have means to print neutral/colorless grey mask with density field given as image. Basically I am talking about special- film based version of flat field correction. Let me read more and dig into the math. Great work!