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Thread: 18 stop Subject Brightness Range on Tmax400

  1. #1
    Virtually Grey Steve Gledhill's Avatar
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    18 stop Subject Brightness Range on Tmax400

    As part of my periodic checking of my processes I carry out a test which displays the resulting integration of all of my processes. The attached PDF shows the output and confirms just how amazing a hybrid workflow of film and scanning can be. Some of what I choose to photograph has exceptionally wide subject brightness range in which ideally I want to capture detail from the deepest shadows through to the brightest highlights. Typical of such subjects are the insides of churches or cathedrals with the deep shadows under the pews and the brightest highlights in the sunny windows.

    The linked PDF below shows that I can get 18 stops of SBR onto my film and scan the whole range such that all of it is useable. I would agree that the separation at each end of the range is limited – but even for my subject matter, 18 stops is almost always more than I need. It is possible that an even higher range at the highlight end can be accommodated but I haven’t tried.

    I’m providing this information for general interest. I’m not making any point here other than to demonstrate the incredible range capability of film which is then available through a digital workflow. Perhaps everyone is already aware of this?


    If anyone is interested in my workflow which gives rise to my being able to have 18 stops of SBR available to me, it is nothing special or difficult, indeed it is very straightforward:

    Tmax400 5x4 film rated at ISO400 processed in XTOL (1+2) in a Jobo with continuous agitation at 24C for 9 minutes. Scanned in an Epson V700 using Vuescan.

    If anyone interested in how I make the step wedge (linked above):

    This does take careful planning. I photograph a light coloured painted wall in shade. As chance would have it a meter reading for Zone V is second at f64 which falls nicely in the middle of the exposure range that I will be using. I use a standard film holder to the darkslide of which I attach with clear tape an 18 step ruler which allows me move in the darkslide one step at a time. You need to experiment with the empty holder to ensure the 18 step ruler is positioned correctly. I start with the slide almost fully out, except for the first strip which is my “Unexposed” strip in the attached PDF. The first real exposure I make is 1/250 sec at f64 which equates to Zone -2. I then move the dark slide in to the next strip position and make the second exposure which needs to be the same as the first which cumulatively means that strip (indeed all of the rest of the sheet) will have received 1/250 sec at f64 twice – making 1/125 at f64. This gives my Zone -1. Move the darkslide in another strip and this time expose for 1/125 sec at f64. This means this strip and the rest of the sheet will have had a total of 1/60 sec at f64 for Zone 0. I repeat this all the way through to the end. This gives me 18 strips, 1 unexposed and 17 exposed.

    All of this does suggest a few interesting consequences – such as in a hybrid workflow, how should I rate my film. The above shows that if I place my deepest shadow detail on Zone 3 then there are actually 6 further stops below that recordable on the film! So perhaps for general use I could rate my Tmax400 at say ISO 800 or 1600 or even 3200 and still have plenty of shadow detail to play with. The additional speed could come in handy sometimes.

    I did wonder which forum group to enter this into as its really a hybrid workflow. I plumped for Digital.
    Last edited by Steve Gledhill; 11-Nov-2009 at 07:36. Reason: Added last sentence ...

  2. #2
    unexposed darr's Avatar
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    Re: 18 stop Subject Brightness Range on Tmax400

    Thanks Steve!! Your work is beautiful to say the least.

    Kind regards,
    Darr

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  3. #3
    Resident Heretic Bruce Watson's Avatar
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    Re: 18 stop Subject Brightness Range on Tmax400

    I read years ago that TMX had a range of at least 22 stops in the lab. This was before widespread use of scanning, so it was beyond any printing technique of the day to make use of this huge amount of data. It was just a laboratory exercise.

    I'm curious however about how to measure what film actually does. The thing about film and developers is that slope of the response curve. I can manipulate that slope at will using the normal tools of developer, dilution, temperature, and time. Such that an SBR of 18 stops can be crammed into a density range on film of maybe 1.5 (I have no idea what your Dmax actually is, so I'm just using 1.5 as an example).

    The question is, did I actually preserve the full separation between the stops of SBR? Or, how much separation in density do I need between the stops of SBR to record it correctly? Does it have to be a log density of 0.3? Is 0.1 enough? IDK. I never purposefully pursued answers to these questions as I don't seem to be attracted to subjects of such high SBR.

    OTOH, I have done some experiments in trying to optimize my film, exposure, and development for (drum) scanning. What I found is that reduced Dmax was better for scanning. To a point. As I reduced Dmax I got to a point there I was squeezing tonal detail too much and wasn't able to fully replicate it in scanning. IOW you can shoe horn too much SBR into a restricted density range and lose some of it in the process.

    Then came the printing. The restricted range of light reflecting off a paper print is the limiting factor in all this. And that depends mightily on the amount of light available to reflect off the print.

    Where I'm going with this ramble is that really large SBRs get compressed mightily in the final print. In part because of the limited dynamic range of the print -- the laws of physics are the laws of physics and all that. But mostly because we want a decent looking print, which means mid-tone contrast. Which in turn means compression of the shadows and the highlights -- or clipping of some of the shadows and/or highlights. So even though we can record and process so that we preserve all the SBR of the scene on the negative, we can't necessarily show it all on the print. Or even want to show it all on the print.

    But that would be where light boxes and display transparencies come in I suppose.

    Still, good work. TMY-2 is my only B&W film these days. And this is partly why.

    Bruce Watson

  4. #4
    Virtually Grey Steve Gledhill's Avatar
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    Re: 18 stop Subject Brightness Range on Tmax400

    Thank you Darr.

  5. #5
    Virtually Grey Steve Gledhill's Avatar
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    Re: 18 stop Subject Brightness Range on Tmax400

    Quote Originally Posted by Bruce Watson View Post
    I read years ago that TMX had a range of at least 22 stops in the lab. This was before widespread use of scanning, so it was beyond any printing technique of the day to make use of this huge amount of data. It was just a laboratory exercise.

    I'm curious however about how to measure what film actually does. The thing about film and developers is that slope of the response curve. I can manipulate that slope at will using the normal tools of developer, dilution, temperature, and time. Such that an SBR of 18 stops can be crammed into a density range on film of maybe 1.5 (I have no idea what your Dmax actually is, so I'm just using 1.5 as an example).

    The question is, did I actually preserve the full separation between the stops of SBR? Or, how much separation in density do I need between the stops of SBR to record it correctly? Does it have to be a log density of 0.3? Is 0.1 enough? IDK. I never purposefully pursued answers to these questions as I don't seem to be attracted to subjects of such high SBR.

    OTOH, I have done some experiments in trying to optimize my film, exposure, and development for (drum) scanning. What I found is that reduced Dmax was better for scanning. To a point. As I reduced Dmax I got to a point there I was squeezing tonal detail too much and wasn't able to fully replicate it in scanning. IOW you can shoe horn too much SBR into a restricted density range and lose some of it in the process.

    Then came the printing. The restricted range of light reflecting off a paper print is the limiting factor in all this. And that depends mightily on the amount of light available to reflect off the print.

    Where I'm going with this ramble is that really large SBRs get compressed mightily in the final print. In part because of the limited dynamic range of the print -- the laws of physics are the laws of physics and all that. But mostly because we want a decent looking print, which means mid-tone contrast. Which in turn means compression of the shadows and the highlights -- or clipping of some of the shadows and/or highlights. So even though we can record and process so that we preserve all the SBR of the scene on the negative, we can't necessarily show it all on the print. Or even want to show it all on the print.

    But that would be where light boxes and display transparencies come in I suppose.

    Still, good work. TMY-2 is my only B&W film these days. And this is partly why.
    Interesting Bruce. I suspected more that 18 is possible - but who needs it? And it is certainly true that as you squeeze more in you have less separation between tones to work with. Although I have a strong science/maths background I'm not actually interested directly in the numbers. For me it's does it look right, can I work with it, can I improve it. The one thing that is I believe implied by your response though is that all of the image gets compressed for the final print. But that's certainly not always the case. In a lot of my work I do a great deal of selective or local contrast work where I stretch the contrast in the shadows for example. Same for the highlights, and for the mid tones for that matter! This of course gets into the whole business of how well one does selections in Photoshop so as not to make the boundaries of the manipulations obvious. Having all the detail in the negative makes that all possible.

  6. #6
    hacker extraordinaire
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    Re: 18 stop Subject Brightness Range on Tmax400

    Interesting. When I think of high SBRs, I think of overexposing and then underdeveloping the film. I was surprised that you were shooting the film at 400, but then you are saying that you can retrieve information below zone 5 to such an extent that 400 is actually conservative. I also wonder what the contrast is doing at these extreme edges, I wonder what your dmax is, and I wonder how all this relates to making projection silver prints.

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    Re: 18 stop Subject Brightness Range on Tmax400

    I shoot TMY for a great deal of my medium format and large format work (5 x 7 to 8 x 20) and I am constantly amazed at what this film can do. I also expose it at 400 and have never had any problem securing the necessary shadow and highlight detail. If I was given one choice of film to shoot for the rest of my days, TMY would be it without question!

    Rick

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    Re: 18 stop Subject Brightness Range on Tmax400

    Quote Originally Posted by Steve Gledhill View Post
    Interesting Bruce. I suspected more that 18 is possible - but who needs it? And it is certainly true that as you squeeze more in you have less separation between tones to work with. Although I have a strong science/maths background I'm not actually interested directly in the numbers. For me it's does it look right, can I work with it, can I improve it. The one thing that is I believe implied by your response though is that all of the image gets compressed for the final print. But that's certainly not always the case. In a lot of my work I do a great deal of selective or local contrast work where I stretch the contrast in the shadows for example. Same for the highlights, and for the mid tones for that matter! This of course gets into the whole business of how well one does selections in Photoshop so as not to make the boundaries of the manipulations obvious. Having all the detail in the negative makes that all possible.
    You work is very nice, and thanks for sharing, but Bruce is right in that capturing a longer range is possible. Whether you need or want it is another matter. The procedure I use in exposing B&W film in scenes of very contrast is simple , just meter for the deepest shadows where you want detail and develop in a two-bath formula that automatically limits highlight contrast. Regardless of how much the scene is compressed one can scan and manipulate the image file in Photoshop with curves and other controls to increase local contrast at any point on the curve.

    My point is not to suggest that other methods are better than yours, only that there are several strategies that can be used to capture scenes of very great contrast, and assuming one is scanning and then working the file I think all of them can be efffective.

    Sandy King
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  9. #9
    ic-racer's Avatar
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    Re: 18 stop Subject Brightness Range on Tmax400

    Hard to tell from that without seeing the densities plotted out in the standard H&D curve, but in 1986, when I first tested T-max 400 I got about 14 stops of usable curve. So, I'm not sure if this represents any new information. Both my sensitometers I currently use have only 21 step wedges so I have not made a complete curve for "new" T-max.

    You mention placing the deepest shadow on zone III which puts the main image onto the straight line. I have been doing that since T-max first came out in the 80s.

  10. #10
    Kirk Gittings's Avatar
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    Re: 18 stop Subject Brightness Range on Tmax400

    Sandy, what two bath developer do you like.
    Thanks,
    Kirk

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