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  1. #21
    markbarendt's Avatar
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    First, I added 2 red lines meant only to compare the steepness of the shoulders. The upper line is steeper. The steeper line means better separation of tones, it really is that simple.

    Not just the shoulder is flatter, the whole curve is flatter (compressed) with less development. Sure you then use harder paper but there is no gain in detail printed.

    Second, is the captain obvious moment. While the theory can be compared using the Tri-X curve, the real shape of the HP5 curve is different. Its shouldering characteristics are different.

    Click image for larger version. 

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    And the basic shape of the shoulder isn't absolute, it will change depending on your techniques. It can be manipulated. Below is a good article.

    http://www.apug.org/forums/forum216/...-negative.html
    Last edited by markbarendt; 05-28-2013 at 05:25 AM. Click to view previous post history. Reason: Missing words
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  2. #22

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    Quote Originally Posted by PeterB View Post
    I hope this counters claims to the contrary.
    It doesn't.

    You are comparing substantial overdevelopment (which also distorts the curve) to underdevelopment on the graph (development time for normal contrast is 7 3/4 min). A more appropriate comparison would be the bottom two curves. The lowest curve has lower contrast, and more compression of shadow detail too. Curves are not absolutes either. Changing the developer or agitation can change where the shouldering starts.

    You also need to use a curve for the right film. If there is highlight compression on this curve with normal development it is because you exposed past the straight line, which is not what you said in your original post.
    Last edited by Michael R 1974; 05-28-2013 at 07:51 AM. Click to view previous post history. Reason: typo

  3. #23
    sun of sand's Avatar
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    develop in the slowest speed developer you have/can get. Rodinal, pyro
    minimal agitation
    add in restrainers
    these in conjunction can lower your film speed by a couple stops

    I wonder exactly how much speed you can lose before too much causes no development of image

  4. #24
    PeterB's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    It doesn't.

    You are comparing substantial overdevelopment (which also distorts the curve) to underdevelopment on the graph (development time for normal contrast is 7 3/4 min). A more appropriate comparison would be the bottom two curves. The lowest curve has lower contrast, and more compression of shadow detail too.

    You also need to use a curve for the right film. If there is highlight compression on this curve with normal development it is because you exposed past the straight line, which is not what you said in your original post.
    Hi Michael, I was composing a reply to your 2nd last post when this one arrived so I thought I'd quickly chime in before a more thorough reply when I have time.

    I don't think that I have left the straight line portion of the HP5 curve but I calculate it to be right on the edge and any variations in process variables could push it into the shoulder so my goal in slightly under developing would be to ensure I don't hit the shoulder. I know in the TRI-X case I compared the two extremes of over and under development, but that was to show the effect magnified which could/should still exist (if one has a sufficient amount of overexposure) as one transitions from a lower to a higher curve. Because I am unsure if I have encroached into the shoulder at N dev time, I wanted to reduce this chance of doing so by under developing.

    Regarding your comments about HP5's shoulder being different, Ilford have not included any information in their HP5 characteristic curve so we cannot conclude anything but only assume. Even if its shoulder characteristics were different, I would be surprised if the general shape didn't generally follow that shown with TRI-X.

    I will reply more about your red lines later tonight or tomorrow morning (OZ time of course !)

    regards
    Peter

  5. #25

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    I wouldn't suggest that. Soft working developers and/or reduced agitation can make the film shoulder earlier. That's exactly what Peter doesn't want.

    Edit: this is a response to post #23.
    Last edited by Michael R 1974; 05-28-2013 at 08:55 AM. Click to view previous post history.

  6. #26
    PeterB's Avatar
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    Quote Originally Posted by markbarendt View Post

    First, I added 2 red lines meant only to compare the steepness of the shoulders. The upper line is steeper. The steeper line means better separation of tones, it really is that simple.
    Thanks for persevering with me Mark. Unfortunately I don't see why the absolute value of the steepness of the curve in the highlight/shoulder section is the thing to compare. I say this because I will be scaling the ENTIRE curve up or down based on the paper grade I select. For the sake of discussion, consider this scaling process to be proportional across the entire curves by assuming that the paper's transfer function is linear (I know it isn't but just assume it is for this point). So imagine I scale the upper and lower TRI-X curves to a position mid-way between those two curves. The shoulder sections will NOT lie on top of each other, and there will still be less highlight separation in the scaled top curve. I can tell this by observing that the ratio of D2/D6 (=21.3) is less than D1/D7 (=10.9). If they would lie on top of each other those ratios would match. Ignore D3 and D4 as I extrapolated those parts of the curves.

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    As you mentioned I should be comparing the middle curve to one below it, but the effect is too small to observe with the limited data present in those curves. If there was more data in the curves showing shoulders for each dev time then it would be easy to compare two middle curves, but in lieu of that missing data it is not unreasonable to assume the effect we see at the longest dev time exists in the middle curves at their shoulders if sufficient over exposure occurs.

    Quote Originally Posted by markbarendt View Post
    Second, is the captain obvious moment. While the theory can be compared using the Tri-X curve, the real shape of the HP5 curve is different. Its shouldering characteristics are different.
    As I noted above, Ilford have not included any should information in their HP5 characteristic curve so we cannot conclude anything only assume. Even if its shoulder characteristics were different, I would be surprised if the general shape didn't generally follow that shown with TRI-X.

    Quote Originally Posted by markbarendt View Post
    And the basic shape of the shoulder isn't absolute, it will change depending on your techniques. It can be manipulated. Below is a good article.

    http://www.apug.org/forums/forum216/...-negative.html
    Very informative thank you. At least I know not to reduce my agitation lest I further compress my highlights !

    Time now to walk the dogs and get to bed.

    regards
    Peter

  7. #27
    Thomas Bertilsson's Avatar
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    If you change how you process your film, and you shot a normal contrast scene, your final negative will come out with lower contrast, and the only way you can counter that is to use a higher contrast paper.
    If you develop 'normal' with an overexposed negative, you will retain the full negative contrast, which enables you to print on a normal contrast paper. The only thing you have to do is to open up your enlarger lens, use a stronger light source, or simply just expose the paper longer.

    This gives you MORE flexibility at printing time, because you can still default to a higher grade paper if you need it for artistic reasons. But if you have already used that higher contrast to compensate for a low contrast negative, well you're out of options. Some of it can be remedied by using a high contrast print developer, like Dektol, of course.

    Anyway, if it were me, I would shoot another roll/sheet of HP5+ in similar conditions with the same gross overexposure, and then test my way to the best likely outcome before​ I processed the very important ones.
    "Often moments come looking for us". - Robert Frank

    "Make good art!" - Neil Gaiman

    "...the heart and mind are the true lens of the camera". - Yousuf Karsh

  8. #28
    markbarendt's Avatar
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    Quote Originally Posted by PeterB View Post
    I don't see why the absolute value of the steepness of the curve in the highlight/shoulder section is the thing to compare. I say this because I will be scaling the ENTIRE curve up or down based on the paper grade I select.
    A bigger real difference is easier to get more contrast from, especially if you need to burn in or are fighting against the paper's curve to get that detail printed.

    Quote Originally Posted by PeterB View Post
    As you mentioned I should be comparing the middle curve to one below it, but the effect is too small to observe with the limited data present in those curves.
    The two ideas above are related and the effect is too small to see in real life too. The point is that there is no gain to be had. It's the equivalent of moving your wallet from your left pocket to the right pocket, it doesn't change how much money is in your wallet.

    One reason that I almost never adjust film development/change the contrast rate is that my normal film development (regardless of my camera exposure placement) sets me up to get the best prints from my paper.

    I only move away from my normal paper grade as a last resort. Moving away from my normal print grade compromises the print because the the shape of the paper curve starts changing too. That doesn't mean I won't change paper grade, just that I use it sparingly.

    Quote Originally Posted by PeterB View Post
    As I noted above, Ilford have not included any should information in their HP5 characteristic curve so we cannot conclude anything only assume. Even if its shoulder characteristics were different, I would be surprised if the general shape didn't generally follow that shown with TRI-X.
    You are right that with the info at hand we are guessing a bit, but just because Tri-X 400 shoulders a certain way doesn't mean HP-5 will follow suit. Flip a couple pages from where you got your graph and look at TXP/Tri-X 320 it doesn't shoulder like Tri-X 400 and it is even made by Kodak.

    Quote Originally Posted by PeterB View Post
    Very informative thank you. At least I know not to reduce my agitation lest I further compress my highlights !

    Time now to walk the dogs and get to bed.

    regards
    Peter
    Exactly, that is why in this particular situation the compensating development schemes and developers aren't the right answer.

    A little extra agitation would mitigate a good bit of the process variables that you are worried about.

    Sleep well.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  9. #29

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    Quote Originally Posted by PeterB View Post
    As you mentioned I should be comparing the middle curve to one below it, but the effect is too small to observe with the limited data present in those curves. If there was more data in the curves showing shoulders for each dev time then it would be easy to compare two middle curves, but in lieu of that missing data it is not unreasonable to assume the effect we see at the longest dev time exists in the middle curves at their shoulders if sufficient over exposure occurs.
    You cannot assume that. Development to higher contrasts can distort the upper end of the curve.

    If you compare the two bottom curves there is no obvious shouldering in either curve. Any blips or dips or kinks are insignificant. The curves are meant to be representative averages. Depending on batch, storage conditions etc. you don't know what exact curve you're dealing with anyway.

    You cannot gain information by reducing development vs an approximately normal contrast index.

    Develop normally, or to N-1 if you prefer (we don't even know what your personal "N" contrast index is), and go forth.

  10. #30
    Bill Burk's Avatar
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    Agree that between N and N-1 will serve you well.

    The shoulder is a response of the film to light, it's not necessarily controlled by development. But some developers can create shoulders. You don't want a shoulder.

    You are going to have a dense negative. A dense flat negative may be harder to work with.

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