Compensating developers as a general-purpose solution for scanning?

[rdenney]

I've been doing some serious exploring. I have acquired the 2551 tank and a 2509N reel that I was asking about a couple of weeks ago, and now I'm starting to consider processing techniques. If my intentions were limited to my previous experience, I would look for FP4+ and soup in HC110 dilution B. But one of the things pulling me back to the notion of souping my own black and white is some of the ultra-wide dynamic range being achieved by Sandy King, Ken Lee, Jay DeFehr, and others.

The key to achieving that wide range seems to be to use something like Pyrocat MC in a two-bath process, where solution A soaks the film with developer (the degree of soaking which controls the degree of development), and solution B causes the development action and develops to completion, with the highlights exhausting the absorbed solution A more quickly which provides the compensation. And the chemicals seem to have enormous shelf life. That development-to-exhaustion approach seems pretty compatible with this tank and reel, and the longevity to my very occasional use.

But my question has to do with suitability for subjects. I'm assuming that the compensation action puts a wide toe on the highlights, so that the middle and lower values are pretty conventional in terms of mapping densities to zones, but the highlights, instead of blocking up, are spread more narrowly over a range of usable densities. Am I understanding that correctly? It seems to me that one would use this approach by measuring the shadows and placing the exposure for Zone III or IV and then let the highlights fall where they may, adjusting contrast as needed after scanning. If that is the case, then this seems a pretty good general-purpose approach for a wide-range of subjects, even those that are flat, assuming the use of Photoshop.

Will this process pair up with any good, general-purpose medium-speed film like FP4+?

Rick "making sure he is understanding what he reads" Denney

[Bruce Watson]

Mostly. The toe is the shadow region (low density part of the negative). The shape of the toe is largely set by the film manufacturer. Development mostly effects the highlights (higher density parts of the negative). What you seem to be after is called a shoulder. If I interpret what you wrote correctly, you seem to want more of an S-curve rather than a linear response from your exposures.

Sandy King wrote a nice article in View Camera a few years back about using divided developers for scanning. You might want to dig around and find a copy.

Personally I take a somewhat different approach. I develop TMY-2 in XTOL. I develop to a Zone VIII density of around 1.0. This would be considered maybe a one stop "pull" by old school darkroom workers (like I used to be) and would be somewhat difficult to print in the darkroom. This combination is more linear than S-curve.

Either method comes down to "expose for the shadows and let the highlights fall where they may."

[rdenney]

Mostly. The toe is the shadow region (low density part of the negative). The shape of the toe is largely set by the film manufacturer. Development mostly effects the highlights (higher density parts of the negative). What you seem to be after is called a shoulder. If I interpret what you wrote correctly, you seem to want more of an S-curve rather than a linear response from your exposures.

Okay, I missed the terminology--shoulder is what I meant.

And it's not necessarily something I want, though I'm not opposed to it. I am trying to understand what it does. If the response is linear, then the S-curve will have to be applied in Photoshop. Keeping it linear would force clipping, unless the middle values are left with relatively little separation. If I set the exposure based on a shadow measured and placed at Zone III, a middle highlight that might normally fall on Zone VI or VII might show density more like Zone V if the response is linear and 20 stops of scenery brightness are compressed into 10 zones of print tonality. I was assuming that zones and stops would approximately align in the middle values, but perhaps not.

But in the examples I've seen, the tonal separation in the highlights is definitely there, but more subtle than the separation in the middle values, suggesting that somewhere along the line, the response curve acquires an S shape. Maybe this is done in Photoshop.

I knew of Sandy's article but do not have that issue and I can't find any online copy of it. I have read much of what Sandy has written on the Pyrocat website and on various posts here.

Mostly what I want to know is whether the approach I've outlined works for general-purpose films and general-purpose subjects, with the proviso that contrast can be increased on the computer by a greater amount than in a darkroom. And I want to know if it works with middle-of-the-road films that are cheap and available, like FP4.

Rick "not wanting to build basic technique around what most consider a specialized approach" Denney

[Jay DeFehr]

Hi Rick,

While I'm flattered to be mentioned alongside Sandy and Ken, my work has little in common with theirs. I know almost nothing about scanning, and make my negatives to print in my darkroom. I scan some of them for archiving purposes, and for web posting, but most of my scans fail to meet even that modest standard. And so, I'm as interested in seeing the responses to this thread as you are!

[Bruce Watson]

If the response is linear, then the S-curve will have to be applied in Photoshop. Keeping it linear would force clipping,...

By what? What's clipping? If the scanner is clipping, it's typically because the operator set the software to clip. A not unreasonable thing to do in some cases. But it's not required, nor inherent in developing film. Most scanners can see through densities over 3.0, and if your B&W film is that dense, you're likely going to find other interesting artifacts from the abuse.

In my experience, nothing you can do to the film in processing can cause any kind of clipping in a scanning workflow.

unless the middle values are left with relatively little separation. If I set the exposure based on a shadow measured and placed at Zone III, a middle highlight that might normally fall on Zone VI or VII might show density more like Zone V if the response is linear and 20 stops of scenery brightness are compressed into 10 zones of print tonality.

This is somewhat of a non sequitur.

In darkroom printing, the negative is an intermediary. Its function, among other things, is to translate the subject brightness range (SBR) into a density range that closely matches the capabilities of the photo paper. Accomplishing this, accurately and precisely, is why Archer and Adams invented the Zone System. The point is to make it relatively easy to make a print from a given negative that meets the vision of the photographer.

In digital, this paradigm is a moot point. The negative doesn't have that duty -- there's nothing to match to. In digital, all we want is a negative that's relatively easy to scan. That typically means that a negative optimized for scanning has a smaller density range than a negative optimized for the wet darkroom.

But the important point here is that the negative has no duty to match its density range to the print paper. That duty falls to the scanner, not the negative. And the scanner can typically read through whatever density range you can through at it. This is because scanners are almost always optimized for color transparencies. And trannies have a density range that is wall beyond the range for B&W negatives.

So what happens is, the scanner reads the film and translates the density range it sees, be it a range of 0.3 or 3.0, into a digital range of 0-255 (if 8 bit), or 0-65535 (if 16 bit), etc. This digital range is an *exact fit*, by definition, to the printing substrate, whatever it may be.

I'm just sayin' that it's a mistake to think of the digital workflow in terms of the darkroom workflow. They are not analogous.

...in the examples I've seen, the tonal separation in the highlights is definitely there, but more subtle than the separation in the middle values, suggesting that somewhere along the line, the response curve acquires an S shape. Maybe this is done in Photoshop.

Typically film is scanned to capture all that is there. This results in a "flat" capture. Using a photo editor like photoshop, one can clip the shadows and highlights as appropriate, and apply whatever curves one wants to increase/decrease contrast, to bump up or down contrast in a given area of tones, etc.

Mostly what I want to know is whether the approach I've outlined works for general-purpose films and general-purpose subjects...

Yep. It does. As they say, there are many paths to the waterfall.

[Jay DeFehr]

In digital, all we want is a negative that's relatively easy to scan. That typically means that a negative optimized for scanning has a smaller density range than a negative optimized for the wet darkroom....Most scanners can see through densities over 3.0, and if your B&W film is that dense, you're likely going to find other interesting artifacts from the abuse......This is because scanners are almost always optimized for color transparencies. And trannies have a density range that is wall beyond the range for B&W negatives........In my experience, nothing you can do to the film in processing can cause any kind of clipping in a scanning workflow.

Bruce,

I hope you'll be patient with a very novice scanner, and explain the apparent discrepancies above. If scanners are optimized for density ranges beyond those typical for B&W negatives, why would a negative optimized for scanning have a smaller density range than one optimized for printing? In my own very limited, very amateur experience, my negatives that scan best are the ones that also print best. I'm willing to accept that this can be chalked up to my poor scanning/editing skills, but the underlying principles escape me.

[Ken Lee]

Sandy has pointed out that using Divided Pyrocat works nicely for roll film, because SBR values vary from shot to shot. For sheet film, it's better to use divided developer only when necessary. I have settled on Pyrocat HD. I used it normally for normal scenes, and divided when necessary. Why ?

In my view, the fewer the adjustments we make, the better. The earlier we make them, the better. There's a reason why the Zone System and BTZS encourage us to expose and develop a negative which prints on Number 2 paper: we're at the sweet spot of the entire process, where tones are the most... lovely.

By that reckoning, exposure and development of the negative should come as close as possible to perfect. Subsequent corrections can be applied either in the darkroom or scanner, but images look their best when further corrections aren't needed.

With digital workflow, further adjustments can be made in the image editing software. I prefer to keep these to a bare minimum, because aesthetically, upstream corrections are best. Images made this way, have a natural quality to them, a sense of presence ad luminosity.

[rdenney]

Typically film is scanned to capture all that is there. This results in a "flat" capture.

Yes, of course. I've been scanning film for a very long time and that part of the process I'm familiar with. But I practiced the Zone System long before that, though not necessarily with the density measurements that many attach to that system (I could never afford a densitometer in those days), instead thinking of it as a tool for mapping subject brightness to previsualized tones in the print.

I don't really see much difference between conventional methods and computer methods in terms of implementing the Zone System. Let me lay out my thinking and see where it leads.

Let's say we were going to print on Grade 2 paper. If we visualized EV 5 subject brightness as Zone II, let's say, then we would expect EV 10 subject brightness to fall on Zone VII, with a few assumptions. These assumptions are: 1.) Each zone is one stop of exposure different from the adjacent zones, 2.) we develop the film and calibrate our technique so that those one-stop differences yield densities that when printed on Grade 2 paper result in tones that look like Zone II and Zone VII, and 3.) we don't do anything to change the brightness relationship between those two parts of the subject.

This also assumes, of course, that the film provides usable densities at ten stops of subject brightness. That was pretty close to my experience with FP4 and HC110B developed in deep tanks, as I used to do years ago. "Usable densities" means that I can print on normal photographic paper without the highlights blocking up (a term I used decades before digital methods) and without losing shadow detail.

"Usable densities" are different for scanning, of course, and nothing I said suggested otherwise. But the concept is the same. Generally, negatives for scanning should be thinner, because if they are too thick the sensor in the scanner loses the ability to record a high enough signal/noise ratio to separate the tones. This is the same as a negative being so dense that when we try to print through it the grain overwhelms tonal gradation. So, "usable densities" for scanning means that the scanner is able to distinguish the tones represented on the film.

I get all that.

But I'm reading where Sandy and others are getting usable densities over a range of more like 18 or 20 stops of subject brightness range. Again, "usable densities" means that the scanner is capable of distinguishing the tones represented on the film. If that's the case, then I still have to visualize 10 zones in the final print. I will have to figure out how to map those 20 stops of subject brightness onto those 10 tonal zones from maximum black to paper white.

Conventionally, we map subject brightnesses to print tones by using a range of techniques. We might process the film to capture 12 steps instead of 10. We might move a Zone VII blue sky to Zone III by using a red filter. Green foliage that falls on Zone III might be coaxed up to Zone V by using a green filter and placing all the other subject brightnesses on a lower zone. All of us who have explored the Zone System using conventional wet processes have learned those techniques to one degree or another.

Now, to the assumptions I stated at the top, which are perhaps wrong. I assumed that when using a compensating developer like Pyrocat the densities in the middle values would vary about like they used to, and the densities in the highlights (particularly), instead of becoming unusably dense, would now remain within the range of "usable densities" for scanning (or for conventional printing, for that matter). So, if I place EV 5 on Zone II, EV 10 might still fall on Zone VII, but EV 14 might fall on Zone VIII, and EV 16 might fall on Zone IX, if I don't do anything to adjust them (the equivalent statement to "printing on Grade 2"). Those numbers imply a broad shoulder on the characteristic curve.

The alternative is that if I place EV5 on Zone II, EV 10 will fall on Zone V instead of Zone VII, because the 20 stops of subject brightness are more linearly distributed across the range of "usable densities".

I think the reason my question isn't making much sense to you (or anyone else) is that we have so much control over input and output tones after scanning that once we develop such that the densities are 1.) within the range of usable densities for scanning and 2.) different enough so that the scanner can distinguish them, we've done all we need to do to give ourselves the control we want in Photoshop. So, in the end, it doesn't really matter if the response is linear or not--a push in the Curves command makes it whatever we want.

My concern was that the densities in the middle of the range, where I would want good separation for flat subjects, would be so close that I would not be able to spread them out. That would make this process not so good for flat subjects.

Rick "thinking out loud, a dangerous practice" Denney

[Henry Ambrose]

snipped a bunch.....

In darkroom printing, the negative is an intermediary. Its function, among other things, is to translate the subject brightness range (SBR) into a density range that closely matches the capabilities of the photo paper. Accomplishing this, accurately and precisely, is why Archer and Adams invented the Zone System. The point is to make it relatively easy to make a print from a given negative that meets the vision of the photographer.

In digital, this paradigm is a moot point. The negative doesn't have that duty -- there's nothing to match to. In digital, all we want is a negative that's relatively easy to scan. That typically means that a negative optimized for scanning has a smaller density range than a negative optimized for the wet darkroom.

But the important point here is that the negative has no duty to match its density range to the print paper. That duty falls to the scanner, not the negative. And the scanner can typically read through whatever density range you can through at it. This is because scanners are almost always optimized for color transparencies. And trannies have a density range that is wall beyond the range for B&W negatives.

I like to think of the negative as the translator to the paper -and- as the translator to the scanner. For scanning the negative must fit its captured scene information into the range of the scanner. Once the scan is done you're gonna shoehorn the scan's range onto the paper using PS. Printing is the big flattener of range.

So in my mind the negative has the same duty to the scanner as it does to the darkroom paper.

You've got to get the scene range to the scanner. The better the density ranges fit the better and easier your work will be. You can make a dead flat negative and pull it apart to fit the larger range of the scanner or you can make one that fits the available range of the scanner and uses the full range. The second scenario is preferable.

Just because you can fix it in PS doesn't mean you should. Make negatives that fit the scanner as if you were making negatives to fit paper. Life will be good.

You do this by a little experimenting to see how your equipment works together. Its not really any different from darkroom work. I don't think you need to go to extremes in developers and techniques to get good pictures. There may be times when you want to do something special but mostly spend your energy on making a good picture that is contained in a good negative that your scanner can read.

[rdenney]

Sandy has pointed out that using Divided Pyrocat works nicely for roll film, because SBR values vary from shot to shot. For sheet film, it's better to use divided developer only when necessary. I have settled on Pyrocat HD. I used it normally for normal scenes, and divided when necessary. Why ?

In my view, the fewer the adjustments we make, the better. The earlier we make them, the better.

Ken, thanks for responding. You can see from my lengthy response to Bruce (which was typing and correcting while you typed this) that you have hit the exact point I was asking about. If I use the divided development for flat scenes, I may have to really spread them out in Photoshop, and that opens the door to posterization, but even without that, to uneven tone as normally invisible variations become visible.

So, single-bath for normal-flat scenes, and divided bath for normal-contrasty scenes.

Rick "appreciative" Denney