Improving shadow detail due to reciprocity failure in very long exposures?

[DavidStephenson]

Hey hive brain, I need help. I have been working on a project involving daytime exposures of up to 6 hours and of course there is lots of reciprocity failure. I am working on 5x7 Delta 100 and FP4 in HC110 1:79 with greatly shortened development times, individually tray processing sheets with continuous agitation as I was having problems with mottling in continuous tone areas like skies. I am scanning for digital printing and I wonder if the scanning process heightens some of this, as it didn't seem to be a problem back when I made silver prints. In the late 1970s when I first worked in LF I used TriX developed in a two step with D23 and Sodium Sulfite bath, resting the film in the second bath without agitation. Great shadow detail but they were conventional exposures, and I would rather stick to HC110 with its long shelf life. Any ideas for improving the shadow detail which is terrible? Maybe an even lower dilution and rest periods without agitation, another film/developer, or???

[xkaes]

Welcome to the FORUM.

Can you tell us more about how you end up with six hour daylight exposures with Delta 100 film? I would think that at that level of exposure to the film there would be no way to compensate adequately.

[DavidStephenson]

Neutral density filters.

[DavidStephenson]

I am controlling highlight density fine, the only problem is with shadow density.

[Mark Sawyer]

Stand development. It gives more development in the shadows than the highlights.

[teathomas]

I think it would help if we understood what you’re doing how you’re doing it and what you hope to accomplish by doing it that way. Basically, what is the goal here?

[DavidStephenson]

Yes I was thinking down that line as well. I used to process 6-8 sheets at a time and shuffle through them so in effect the middle sheets where getting no agitation, but when I went back to b&w I seemed to be getting increased edge density with that method so went to the single sheet and constant agitation. The stand development is a bit like the D23 and Sodium Sulphite bath with no agitation that I used to use. I will give it a go, thanks. Anyone out there tried it with HC110?

[DavidStephenson]

The goal is to get good continuous tone negatives with extremely contrasty subject matter.

[Vaughn]

Keep your exposure time the same but reduce the filtration (and/or increase aperture). First step is to get enough exposures in your shadows where you want them. Then figure out what to do for your high lights.

[DavidStephenson]

Unfortunately the shadows really can't be exposed as much as I would like with the inherent reciprocity failure of the very long exposure. I am probably trying to get something like an N-6 contraction and when you reduce development activity to such a low level other problems like unevenness creep in. It may be that HC110 with hydroquinone as the primary developing agent is a problem despite the low dilution and I should go back to the past and try D23 which only has the low activity developer metol along with sodium sulphite, and a second bath of borax. And lower the agitation with the D23 but not eliminate it altogether. I have lost my notes from the old days when I used it but I think the method is in Ansel Adams The Negative which I read a long time ago. I have ordered a copy.

[revdoc]

Different films have different reciprocity failure rates, so a change of film might help. TMX has a good reputation in this regard. Preflash might also bring the shadow detail up.

For a very low contrast developer, ascorbic acid and sodium carbonate might be worth a try. I use it with lith film to make continuous tone negs.

BTW, I like your work.

[Vaughn]

I think there is a better way to approach this. If I understand the situation (because you are adding the neutral density filters), you seem to want the exposure to be 6 hours.

I suggest figuring out what exposure is needed by the scene so that after the reciprocity failure factor is included, the new time is 6 hours.

For example, below is Michael Jenna's recommendations for reciprocity corrections from his experience with night photography. Note that for Tri-X, he suggests that for a metered exposure of 20 minutes the film should be exposed for 4 hours to correct for reciprocity, and a metered 40 min exposure becomes 8 hours. Splitting the difference, if you were using Tri-x and needed a 6 hour exposure, then you would add just enough neutral density filters to give you a meter reading of 30 minutes. You would then make your 6 hour exposure, reduce the development to keep the highlights, and you'd have your shadows right where you want them. With a little testing, of course.

[sjbadham]

That's a tough one. You're battling two problems simultaneously: 1) reciprocity failure, which adversely affects shadows more than highlights, is requiring you to use compensation development in an attempt to recover shadows without blowing out the highlights; and 2) the use of compensation development (i.e., dilute developer with little agitation) is resulting in uneven development in continuous tone areas (e.g., clear blue skies).

In my experience, compensation development can only do so much to recover shadows, and the degree of zonal contraction you're attempting (N-6) is probably far beyond the capabilities of any compensation technique. My approach would be to not bother with any kind of extreme compensation and just go with a developer that has intrinsic speed-boosting characteristics (e.g., Kodak Xtol, Ilford Microphen, etc.). That should still get you some shadow recovery while also eliminating uneven development (which to my mind is the bigger problem you want to avoid).

Revdoc's suggestion of using a different film with better reciprocity characteristics is a good one, too, unless you specifically need a six-hour exposure for artistic reasons (e.g., time-lapse movement, etc.). Kodak Tmax 100 is more resistant to reciprocity failure than Ilford Delta 100 (reciprocity compensation of t^1.15 vs. t^1.26, respectively) and is generally considered to be finer grained.

[Vaughan]

The correct way to compensate for reciprocity failure is to open the aperture not extend the exposure time. Nobody does that though, and most reciprocity correction tables adjust time.

Keep the exposure you're currently using and reduce the neutral density (and/or open the aperture) until you get the desired shadow detail. Then adjust development to achieve the desired contrast. Reducing development may change shadow density slightly so some practical tests will be necessary.

Reciprocity characteristics can vary by batch so ideally get all the film you need at the same time, hopefully it will be the same batch.

Fuji Acros was the reciprocity king, extending without correction to over two minutes and only needing half a stop after that. Maybe look into the reciprocity of x-ray film, though I think most are orthochromatic.

[dave_whatever]

The correct way to compensate for reciprocity failure is to open the aperture not extend the exposure time. Nobody does that though, and most reciprocity correction tables adjust time.

Not least because in practical terms opening up the aperture means reducing depth of field, which can totally change your image. But usually you're shooting at a given aperture because you need it for depth of field, hence you're left with lengthening exposure.

Provia is another film with exceptional reciprocity, better even than Delta or Across, getting to 4mins before you need to add a third of a stop. Probably of no use to the OP here though...!

[jnantz]

Yes I was thinking down that line as well. I used to process 6-8 sheets at a time and shuffle through them so in effect the middle sheets where getting no agitation, but when I went back to b&w I seemed to be getting increased edge density with that method so went to the single sheet and constant agitation. The stand development is a bit like the D23 and Sodium Sulphite bath with no agitation that I used to use. I will give it a go, thanks. Anyone out there tried it with HC110?

I haven't tried it with the developers you have mentioned and I have never used ND filters but I regularly make very exposures with both film and paper negatives as part of my "studio practice". I develop everything in caffenol c (teaspoon measure not a scale) with about 20cc / L of whatever print developer you have lying around. the negatives come out OK. caffenol C has vit c in it so it's low contrast. I've also split development with similar long exposed negatives .. this is split with D72 or ansco130 ... 1:10, like you would use them for film but instead of the normal 10 mins I shuffled for 5 minutes and then went into the caffenol and shuffled for the remaining 5 minutes, the films and paper come out OK too... it's like divided d23 but better.

good luck with your developments!
John

ps. you might search for people making "solargraphs" to see how they might develop out their film

[paulbarden]

I think pre-exposure is a good technique to experiment with.

[MartyNL]

An aspect that I've noticed with long exposures and wide angle lenses in particular, also pinhole, is the increasing fall-off in illumination towards the outer edges, creating a vignetting effect.
Also, with such lengthy exposures, there could be more issues with non-image forming light.

[xkaes]

I think there is a better way to approach this. If I understand the situation (because you are adding the neutral density filters), you seem to want the exposure to be 6 hours.

I suggest figuring out what exposure is needed by the scene so that after the reciprocity failure factor is included, the new time is 6 hours.

For example, below is Michael Jenna's recommendations for reciprocity corrections from his experience with night photography. Note that for Tri-X, he suggests that for a metered exposure of 20 minutes the film should be exposed for 4 hours to correct for reciprocity, and a metered 40 min exposure becomes 8 hours. Splitting the difference, if you were using Tri-x and needed a 6 hour exposure, then you would add just enough neutral density filters to give you a meter reading of 30 minutes. You would then make your 6 hour exposure, reduce the development to keep the highlights, and you'd have your shadows right where you want them. With a little testing, of course.

I think this would be the way to go. With very dim light or excessive ND filtration you reach a point where there aren't enough photons (AKA, light) hitting the silver halide to cause a reaction, and no adjustment in development will change that. You might have reached that point with that film. You could try pre-exposure (as has been suggested) or chemically pre-sensitizing the film -- which will create some density where there is none now.

[Drew Wiley]

You might want to query an astro photography forum where they routinely deal with long exposure issues. There might be some old timers still around who recall how they did it in film days. I'm not personally going to go into hypersensitization, because I don't have any experience with it. Early TMax 100 was made in glass astro plates, which furnishes a clue. There must be something in literature somewhere which describes how they developed it. Don't expect anything in those old Ansel Adams books to be relevant; even the films were different then.

Acros is no longer made in sheet sizes; but you might get lucky finding some. I have tested batch to batch TMax quality control using careful densitometry, and so far the consistency has been superb. But once you try using colored filters for very long exposures, a lot of things change, gamma-wise, and need to be specifically tested for.

[revdoc]

I've seen some of David's work. Long exposures are a big part of what he does.

David, Drew mentioned hypersensitisation. This was big in astrophotography back in the 80s and 90s. It would help you with your problem, but it's not a skillset that many people have these days. The local astronomical society might have some older members who can advise, but it's a long shot.

[jnantz]

I've seen some of David's work. Long exposures are a big part of what he does.

David, Drew mentioned hypersensitisation. This was big in astrophotography back in the 80s and 90s. It would help you with your problem, but it's not a skillset that many people have these days. The local astronomical society might have some older members who can advise, but it's a long shot.

hi revdoc:

I was going to suggest hypering with HOHO but there were folks who were doing that over on apug / photrio about 7-10 years ago, if it is the same thing (it involved warming hydrogen peroxide and "steaming" the film in it's vapors ) ... not a skillet ( or skill set ) many people have these days is an understatement ! I don't think the people who were doing it got any increased sensitvity in their film at all .. (then again, they were probably doing it wrong ), all they got was a mess..

[Bruce Watson]

Hey hive brain, I need help. I have been working on a project involving daytime exposures of up to 6 hours and of course there is lots of reciprocity failure. I am working on 5x7 Delta 100 and FP4 in HC110 1:79 with greatly shortened development times, individually tray processing sheets with continuous agitation as I was having problems with mottling in continuous tone areas like skies. I am scanning for digital printing and I wonder if the scanning process heightens some of this, as it didn't seem to be a problem back when I made silver prints.

Reciprocity "failure" is simply a lack of sufficient photons to create a latent image. If there's no latent image, the developer has nothing to develop, which is where empty shadow areas come from. So the first thing you have to do is increase exposure in the shadows. You don't wanna, but no latent image = no image on the print. Just the laws of physics talking to ya.

Next up is HC-110, which is a fairly aggressive developer. I've found HC-110 to be fairly difficult to control even in very dilute form. It just acts too quickly. I found the ascorbic acid developers like XTOL much easier to control and they dilute well (as long as you don't have much iron in the water, which is a good reason to use steam distilled water to mix and dilute ascorbic acid developers). But, to each their own; just find something you can control so you can avoid mottling.

If your highlight density is still making you twitch, you may get better results from stand development (that is, *not* HC110 no matter how dilute), so that the developer (not my field, but look up stand development and you'll find developers that are popular for stand usage) exhausts itself in the highlight areas and can't create any more density there, but isn't yet exhausted in the shadow areas so it's trying to keep adding density there. This should "compress" your density range somewhat. How much depends on too many things to discuss here -- there are books that cover all the stuff with stand development. Also look at two-part development. Similar results to stand, but created differently? My memory isn't very solid on this because all I ever did with two-part development was research it, I never actually used it myself.

But the thing you're missing I think (and boy could I be wrong), is that scanning the film will cure most of your ills. Sacrilege, I know. They don't call me a heretic for nothin'.

So, what to do? First thing is you must have enough exposure in the shadows to form a latent image. Without that, nothing else will help.

Then, shorten developer time as far as you can until you get uneven development. This will bring down your highlight density. Don't worry about how much density that turns out to be. Let the scanner deal with that.

Once you get to the scanning stage, you'll get your best results by drum scanning. Why? Almost all drum scanners I've dealt with let you set their log-amp range -- you set their white and black points, and the scanner applies it's full dynamic range to whatever is in between (whereas most flat bed scanners typically let you set black and white points as well, but this does *not* effect their log-amp range, which can be painful for difficult images like yours). If your negative density range runs from, say, 0.2 to 3.2 (impossible to print in the darkroom), the scanner won't care and will just do what you tell it. When you bring this scan into your photo editor, what you get is a range of 0-256 (the software is old and almost always displays 8-bit values even if the underlying image is 10, 12, 14 or even 16 bit, don't let it worry you). All the information recorded on the negative (between where you set your white and black points) will be there for you to work with, even if your scene's dynamic range was 12 stops. Or 20 stops (yeah, good luck with that, but the TMX and TMY films can do it even if it takes laboratory equipment to read that deep into the highlight density (I remember reading this from Kodak back in the 1980s in one of their tech. bulletins). This *might* be enough to do what you want.

If it's not enough, change to stand development with a stand development developer workflow to bring the highlight density down a bit more.

And that, seriously, is about as far as you can go with "normal" photography.

Next up, do the astrophotography stuff and try to raise the film's sensitivity so you need fewer photons to form a latent image. But at this point my knowledge is exhausted.

Bottom line: Expose for the shadows and develop for the highlights. Like it always has been since John Herschel invented fixer.

[DavidStephenson]

Thanks for all your suggestions folks - a lot of this I know and have tried already except for going back to the 2 step Stockler method I used in the 70s and 80s which is nicely detailed in another thread I found. I am hoping that this lower activity developer manipulation in combination with increasing the exposure will allow me to reduce highlight density sufficiently for my purposes (yes, scanning). BTW, TMAX 100 which I used to use in 5x7 seems hard to find, although Kodak still lists it.

[Alan Klein]

Reciprocity "failure" is simply a lack of sufficient photons to create a latent image. If there's no latent image, the developer has nothing to develop, which is where empty shadow areas come from. So the first thing you have to do is increase exposure in the shadows. You don't wanna, but no latent image = no image on the print. Just the laws of physics talking to ya.

Next up is HC-110, which is a fairly aggressive developer. I've found HC-110 to be fairly difficult to control even in very dilute form. It just acts too quickly. I found the ascorbic acid developers like XTOL much easier to control and they dilute well (as long as you don't have much iron in the water, which is a good reason to use steam distilled water to mix and dilute ascorbic acid developers). But, to each their own; just find something you can control so you can avoid mottling.

If your highlight density is still making you twitch, you may get better results from stand development (that is, *not* HC110 no matter how dilute), so that the developer (not my field, but look up stand development and you'll find developers that are popular for stand usage) exhausts itself in the highlight areas and can't create any more density there, but isn't yet exhausted in the shadow areas so it's trying to keep adding density there. This should "compress" your density range somewhat. How much depends on too many things to discuss here -- there are books that cover all the stuff with stand development. Also look at two-part development. Similar results to stand, but created differently? My memory isn't very solid on this because all I ever did with two-part development was research it, I never actually used it myself.

But the thing you're missing I think (and boy could I be wrong), is that scanning the film will cure most of your ills. Sacrilege, I know. They don't call me a heretic for nothin'.

So, what to do? First thing is you must have enough exposure in the shadows to form a latent image. Without that, nothing else will help.

Then, shorten developer time as far as you can until you get uneven development. This will bring down your highlight density. Don't worry about how much density that turns out to be. Let the scanner deal with that.

Once you get to the scanning stage, you'll get your best results by drum scanning. Why? Almost all drum scanners I've dealt with let you set their log-amp range -- you set their white and black points, and the scanner applies it's full dynamic range to whatever is in between (whereas most flat bed scanners typically let you set black and white points as well, but this does *not* effect their log-amp range, which can be painful for difficult images like yours). If your negative density range runs from, say, 0.2 to 3.2 (impossible to print in the darkroom), the scanner won't care and will just do what you tell it. When you bring this scan into your photo editor, what you get is a range of 0-256 (the software is old and almost always displays 8-bit values even if the underlying image is 10, 12, 14 or even 16 bit, don't let it worry you). All the information recorded on the negative (between where you set your white and black points) will be there for you to work with, even if your scene's dynamic range was 12 stops. Or 20 stops (yeah, good luck with that, but the TMX and TMY films can do it even if it takes laboratory equipment to read that deep into the highlight density (I remember reading this from Kodak back in the 1980s in one of their tech. bulletins). This *might* be enough to do what you want.

If it's not enough, change to stand development with a stand development developer workflow to bring the highlight density down a bit more.

And that, seriously, is about as far as you can go with "normal" photography.

Next up, do the astrophotography stuff and try to raise the film's sensitivity so you need fewer photons to form a latent image. But at this point my knowledge is exhausted.

Bottom line: Expose for the shadows and develop for the highlights. Like it always has been since John Herschel invented fixer.
What's log amp range? With a flatbed like the V850, should one set black and white points for the scan or scan flat and let your editing program set the range or does it matter?

[Bruce Watson]

What's log amp range? With a flatbed like the V850, should one set black and white points for the scan or scan flat and let your editing program set the range or does it matter?

Sorry for the delay -- I wrote a long winded reply but the website ate it. That is, it didn't post it due to some timeout or other. IDK. Anyway, time to try again. ;-)

A shorter answer is that the photodetectors on flat-bed scanners and drum scanners mostly operate in different ways. Flat-bed scanners scan the film a line-at-a-time which is much faster than the pixel-at-a-time of drum scanners. Flat-bed scanners are also considerably less expensive, and considerably more modern. Drum scanners ended development more or less at the end of the last century after all.

In either case, the output from the scanner elements has to be read and amplified by some electronics so that it can be digitized. In drum scanners the log-amp (LOGarithmic AMPlification) circuits read the outputs of the PMTs (PhotoMultiplier Tubes). In flat-bed scanners something similar happens.

The difference is that in most flat-bed scanners, at least in the categories below the full blown professional models (the so called "pro-sumer" levels and below) save money and simplify things for the operator by having scanner run at the maximum range it can do all the time (because... color transparencies). So the black and white levels are more or less pre-set internally to the full range of what the scanner can do.

In drum scanners, the black and white points actually set the range that the scanner operates over. Not the full range of what the scanner is capable of, but only between the levels that the scanner operator chooses.

When you change the black and white points with a pro-sumer flat-bed, you are basically editing a histogram like you would in a photo editor program. Moving the end points in from the limits actually throws data away (which isn't usually a bad thing). When you change the black and white points with a drum scanner, all the levels the scanner can deliver are applied to the range of values that the scanner operator specifies. No data is lost.

For example, if a pro-sumer flat-bed is capable of scanning at 12 bits / channel, it will do that across the full range of film density that it can read. Say, from a density of 0-3.4. If your B&W negative only has a density of 0.2-1.2, the resulting scan (after you edit your black and white points) might only be using 6 bits / channel. With a drum scanner, your 0.2-1.2 range would get all 12 bits / channel. The resulting image can exhibit smoother gradation, especially in areas like exposed skies.

So that's the range I was talking about. And with a pro-sumer flat-bed like your V-850 (I had an earlier version, I don't remember what it was called), I don't believe it makes any difference if you set your black and white points in the scanner software before the scan, or in your editing program after the scan. But in a drum scanner it can make a lot of difference, depending on the image, the film, and the processing.

Hope that is more helpful than it might be confusing. If I were good with words I wouldn't need photography so much. ;-)

[popdoc]

As you’re looking for serious “- development”/contraction, reach out to Steven Sherman and his “Power of Process”. His ultra minimal agitation combined with pyro development method provides stunning and most reliable results.

Negatives from minus 4-8 (plus too) are easily in his wheelhouse. No mottling, beautiful microtonalities, etc. He’s your guy!

[Alan Klein]

Sorry for the delay -- I wrote a long winded reply but the website ate it. That is, it didn't post it due to some timeout or other. IDK. Anyway, time to try again. ;-)

A shorter answer is that the photodetectors on flat-bed scanners and drum scanners mostly operate in different ways. Flat-bed scanners scan the film a line-at-a-time which is much faster than the pixel-at-a-time of drum scanners. Flat-bed scanners are also considerably less expensive, and considerably more modern. Drum scanners ended development more or less at the end of the last century after all.

In either case, the output from the scanner elements has to be read and amplified by some electronics so that it can be digitized. In drum scanners the log-amp (LOGarithmic AMPlification) circuits read the outputs of the PMTs (PhotoMultiplier Tubes). In flat-bed scanners something similar happens.

The difference is that in most flat-bed scanners, at least in the categories below the full blown professional models (the so called "pro-sumer" levels and below) save money and simplify things for the operator by having scanner run at the maximum range it can do all the time (because... color transparencies). So the black and white levels are more or less pre-set internally to the full range of what the scanner can do.

In drum scanners, the black and white points actually set the range that the scanner operates over. Not the full range of what the scanner is capable of, but only between the levels that the scanner operator chooses.

When you change the black and white points with a pro-sumer flat-bed, you are basically editing a histogram like you would in a photo editor program. Moving the end points in from the limits actually throws data away (which isn't usually a bad thing). When you change the black and white points with a drum scanner, all the levels the scanner can deliver are applied to the range of values that the scanner operator specifies. No data is lost.

For example, if a pro-sumer flat-bed is capable of scanning at 12 bits / channel, it will do that across the full range of film density that it can read. Say, from a density of 0-3.4. If your B&W negative only has a density of 0.2-1.2, the resulting scan (after you edit your black and white points) might only be using 6 bits / channel. With a drum scanner, your 0.2-1.2 range would get all 12 bits / channel. The resulting image can exhibit smoother gradation, especially in areas like exposed skies.

So that's the range I was talking about. And with a pro-sumer flat-bed like your V-850 (I had an earlier version, I don't remember what it was called), I don't believe it makes any difference if you set your black and white points in the scanner software before the scan, or in your editing program after the scan. But in a drum scanner it can make a lot of difference, depending on the image, the film, and the processing.

Hope that is more helpful than it might be confusing. If I were good with words I wouldn't need photography so much. ;-)

The bold was my question. Others have said that it's best to set the black and white points for the scan rather than afterward as that way more data is accumulated. My theory is that the scanner scans the full range from 0-255 regardless of the settings and just applies black and white points and other settings after the scan when it creates the scan file. So if that's the case, you can scan "flat", and just do black and white adjustments in your editing program afterwards with no difference in data accumulated. What do you think?

[nitroplait]

Wow. Complicated!
Why not just a flash to fill the shadows?
During ultra long exposures with extreme reciprocity failure, one can walk around the scene in dark clothes and flash the shady areas. Just a thought.

[DavidStephenson]

Flash is an interesting suggestion and I used this a lot when I did long night exposures with some earlier bodies of work. However, it has a distinctive look, and anyway these are daytime exposures and the shadow areas are quite far from the camera so that won't really work with the apertures I am using. Regarding setting black and white points with the scan, my best results have generally been to scan the full range then adjust in post. I think my best bet is still to increase my shadow exposure by reducing the ND and increase shadow density/tame the highlights using a two step low activity developer. I will try the D23 two step first and if that doesn't help, explore more exotic options like the "ultra minimal agitation combined with pyro development method". I am also going to try going back to FP4 instead of Delta 100 because although Ilford states the same reciprocity failure factors for both films, the characteristic curves published by Ilford show FP4 with a flatter shoulder which suggests that highlight density tapers off compared to Delta. I used to use TMax 100 but it seems to be no longer available in 5x7. Once again, thanks for all the suggestions. I am confident that i will get there (wherever that is!) in due course.

[Bruce Watson]

The bold was my question. Others have said that it's best to set the black and white points for the scan rather than afterward as that way more data is accumulated. My theory is that the scanner scans the full range from 0-255 regardless of the settings and just applies black and white points and other settings after the scan when it creates the scan file. So if that's the case, you can scan "flat", and just do black and white adjustments in your editing program afterwards with no difference in data accumulated. What do you think?

I think that's probably the way it works, yes. You can do multiple scans of a low density range image -- one full range, the other with black and white points set. Compare in a photo editor. One test that might tell you something is to take the full range scan into your photo editor and apply the same black and white points to it there. Then compare that result to the scan where you set these black and white points at the scanner. If you can't find any difference, you have your confirmation. If you can find differences, pick the one you like best and do it that way. I'm just sayin' that you don't have to guess, you can do the experiment and find out.

[Alan Klein]

I think that's probably the way it works, yes. You can do multiple scans of a low density range image -- one full range, the other with black and white points set. Compare in a photo editor. One test that might tell you something is to take the full range scan into your photo editor and apply the same black and white points to it there. Then compare that result to the scan where you set these black and white points at the scanner. If you can't find any difference, you have your confirmation. If you can find differences, pick the one you like best and do it that way. I'm just sayin' that you don't have to guess, you can do the experiment and find out.

I recall doing something like that years ago, I compared the number of pixels which were the same. That's how I concluded they were. Other people claimed the pixels were different in what they captured, but I don't necessarily agree with them. I found it hard to see a difference with my eyes.

[jnantz]

found it hard to see a difference with my eyes.

I'm the same way Alan, I can't see a lot of the differences a lot of people see, I drink wine that costs less than 10$ a bottle too. the fancy stuff, whether it is photographic or some other connoisseur-istic endeavor ... is pretty much lost on me ..

[Alan Klein]

I'm the same way Alan, I can't see a lot of the differences a lot of people see, I drink wine that costs less than 10$ a bottle too. the fancy stuff, whether it is photographic or some other connoisseur-istic endeavor ... is pretty much lost on me ..

Cheap wine affects your vision. ;)

[jnantz]

Cheap wine affects your vision. ;)

its all about vision, man .. gotta open your eyes and see.
cheep wine, sparkling water, tomato juice .. doesn't matter .. just gotta see.

[Andrew O'Neill]

I would experiment with pre-exposure. It's a pity we can no longer get Acros in sheet film... A half stop more exposure would be all that is needed.

[rdenney]

Back to the idea of auxiliary lighting. A flash will almost always create hard-edged shadows that probably will upset the look of a six-hour exposure.

But what about painting with light? An advantage to a six-hour exposure is that you can move around in the frame without leaving a trace. A bright studio light with an opaque reflector (to prevent any direct light travel back to the camera) could be used to paint light into the parts of shadows that need some detail. Adams used it for long-exposure interior photographs to prevent any hint of hard shadows.

Rick "good luck" Denney

[Willie]

Have you tried Kodak T-Max 100 for this?
Two friends doing long exposures - 2-8 hours with 8x10 in dimly lit interiors found it worked better for them than any other film. They tried a few before undertaking their project. Said that after abotu a 20 minute exposure the T-Max 100 was apparently the "fastest film" they found. Your outdoors may be different as you have a lot more light to work with - they were in very dim rooms, had to use a flashlight to focus & compose before making the exposure.

[Thodoris Tzalavras]

The replies suggesting a reduction of ND filtering, so that the shadows are better exposed, and then dealing with the over-exposed midtones and highlights with development make the most sense.

There is also the "SLIMT" method of reducing highlights in the latent image before developing, which could further help in keeping the highlights within range.

Regarding, pre-exposure:

I tested pre-exposure some years ago for multi-hour night landscapes on ortho film, but gave up on it because it also enhanced the effect of light pollution, which is a big problem where I am.

In your case, since you're shooting in daytime and shadows are predominately blue tinted, I would suggest testing for the threshold pre-exposure of your panchromatic film using a blue filter (for example a blue only exposure with an Ilford MG 500 head).

Initial testing for a threshold exposure can be done in the darkroom alone, without the actual 6 hour expose.
Once you have a ballpark figure, you can bracket a whole sheet of film in the same way that you'd expose a test-strip, starting with at least 2 stops under and going up to 2 stops over that ballpark figure.
Placing a single 6 hour exposure ontop of that (preferably of a scene with shadowed subjects overlapping all the individual pre-exposures) will give you a good idea of whether it warrants further investigation or not…

By the way, even though T-max 100 does seem to be currently out of stock in most places in anything larger than 4x5", there are (or at least were) dealers who place special orders directly from Kodak on a semi regular basis, so there might still be a way to order some in 5x7", if that's indeed the best film for your project…