HP5+ over exposed by 4 stops, will my recovery plan work ?

Discussion in 'Exposure Discussion' started by PeterB, May 26, 2013.

  1. PeterB

    PeterB Subscriber

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    Hi folks,

    I was rather annoyed at myself to discover that I over exposed a 120 roll of HP5+ by a whopping 4 stops ! The good news is that I think my highlights will not be compressed at all but I wanted to run my solution past you.

    The SBR was 7 stops from Zone II to VIII inclusive which would have otherwise lead to Normal (N) development time. In short I plan on reducing the film development time to be that for N-1 which in my process will lower the gamma from 0.5 to 0.4

    Below you can see my analysis, but I am amazed that I can still keep my scene in the straight line portion of the curve by forcing a minor reduction to its CI/gamma/slope. I will just print using 1 grade harder MG filter. What am I going to lose out on here ? This seems too easy to recover from.

    ** warning that a bit more theory and maths will now follow... **

    I have analysed the HD/characteristic curve of HP5+ and it is linear out to at least a density of 2.1 log units which has basically been my saving grace here. Normally a neg exposed for N development in my process would result in a density ranging between 0.3 and 1.35 on the neg. [gamma=(1.35-0.3)/(7x0.3)=0.5]. 1.35 is nowhere near 2.1 but 4 stops over exposing would put the density right on 2.1, however if I reduce the gamma to 0.4 and calculate the range for Zone II to IX, you will see it comfortably makes it in. I am calculating from zone II up to Zone IX (i.e. an 8 stop range) as I want to include even the last nuance of detail in my highlights. So here is the formula:

    Gamma=0.4=(D_zone_IX_end - D_zone_II_start)/((4+8)x0.3)
    0.4=(D_zone_IX_end - 0.3)/((4+8)x0.3)
    D_zone_IX_end = 1.74.​


    Now because D_zone_IX_end<2.1 , I should be OK. In fact because I still have a bit of wiggle room I could develop to N-0.5 which would give D_zone_IX_end = 1.92 Developing for N would put D_zone_IX_end right at a density of 2.1 and permit no room for any error in dev time/temperature/age/minor film exposure variations etc.


    regards
    Peter
     
  2. michael_r

    michael_r Subscriber

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    Exposure determines where the values fall on the characteristic curve. Development alters total and local contrast (ie the shape and slope(s) of the curve). So minus development compresses contrast. It does NOT move the exposure range down the curve.

    Therefore in a case where you don't need to reduce contrast, if you are going to reduce development, do it because you want to slightly offset any increased graininess associated with overexposure. Other than that it will not improve anything. All it can do is decrease local contrast, particularly in the highlights, which is exactly what you indicated you didn't want. In other words, all reduced development can do is reduce the slope (ie contrast) of the straight line, and also shorten it.

    N-1 is a pretty mild contraction, but I'd still say develop normally. From the perspective of sensitometry, you can't correct for overexposure with reduced development.
     
  3. markbarendt

    markbarendt Subscriber

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    I'd go normal too.
     
  4. PeterB

    PeterB Subscriber

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    Thanks Michael and Mark.

    Michael, have a look at figure 4 here. It shows graphically what I thought happens to the curve's shoulder with increasing development times. Basically the shoulder moves up and to the left of the HD curve (Dmax of the film eventually causes the shoulder to clip as dev time is increased). Two other examples. Here showing the HD curve for TriX and another example using AZO paper (which I assume could be applied to film in general) here in chart 3 . Both show the shoulder moving up and to the left with increasing development time. If I draw a vertical line say mid way along the straight line portion off all those curves and then start moving to the right (up) each curve, one will traverse a longer stretch of the straight line portion on the traces with less development. Note that I'm not seeking to shift the exposure range down the curve, I always lock the exposure range to the horizontal axis. Less straight line portion this means less over exposure latitude.

    Finally on p. 230-232 of WBM 2e there are also some pertinent notes on Exposure Latitude. Near the end of p.231, we read "when in doubt it is better to err on the side of under-development allowing for more exposure latitude".

    regards
    Peter
     
  5. Bill Burk

    Bill Burk Subscriber

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    In general, you take a normal scene and develop N-1 and use a higher paper grade or filter to print.

    That's a general reciprocity idea.

    You figured that you are on the straight line. So you could develop Normal and use the same paper grade or filter as if you had exposed normally. The contrast should be the same as you would have normally gotten. You would develop less if you expected a longer than normal scale subject would have shadows still at 0.3 and highlights at 2.1, but yours isn't going to have a thin shadow.

    You will have a density 1.05 to 2.1 if you develop normally, and the only difference from a perfect normal negative that you would print for 16 seconds is that you will print this one for 40 seconds.

    I am generalizing however. You will have more grain. To reduce that, your original plan to develop N-1 is fine.
     
  6. PeterB

    PeterB Subscriber

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    Thanks for your observations Bill. I didn't know that increased exposure results in more grain.
    A max density up to 2.1 is right on the cusp of HP5+'s shoulder and leaves me no room for deviations/error in other process variables which is why I am inclined to dev to N-0.5 or N-1.

    regards
    Peter
     
  7. Tom1956

    Tom1956 Inactive

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    I am nobody qualified to interject with any sensitometric evidence. Only intuition. And I'd tend to believe a lot of picture information and local contrast has been pushed up or over the shoulder. And the only hope would be undervelopment. Trading one bad thing for another in this case is the only possible hope. The first remedy that sprang to mind was pyro, but I have no experience with the stuff to back up my thought. However, "normal" development is something I'd discount immediately and close my mind to it.
     
  8. markbarendt

    markbarendt Subscriber

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    Peter I think you are thinking too hard on this.

    If these shots are really that important just shoot another roll the same way in a similar situation, cut it in half develop both ways and see which you prefer.
     
  9. PeterB

    PeterB Subscriber

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    Mark, they REALLY are that important. It will take me another 2 days to travel out and back to get the shots again ! This exercise will provide all of us with valuable insights to apply next time we accidentally overexpose a roll of film by at least 3-4 stops. If my approach turns out not to work I suppose I could spend the time taking them again, but at least I want to give this roll the best opportunity for success.
     
  10. markbarendt

    markbarendt Subscriber

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    I feel for you, many of us, me included, have already made these mistakes, we know what happens with our subject matter and our techniques and our tools. For me 4 over is an oh well got a little extra grain moment, 4 under though, now that gets me grumpy.

    There are lots of variables here, the only real way to see what you're going to end up being acceptable given your subject matter, using your techniques and your tools, is to test.
     
  11. heterolysis

    heterolysis Member

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    I recently (and accidentally) overexposed a very important roll three stops and pulled lots in development to compensate (4min instead of 9 in DD-X). I had never done anything like this before, but the shots were all passable. It worked to my advantage in the end because the contrast of the shots would have been far too high otherwise. The grain wasn't bad either.
     
  12. LJH

    LJH Member

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    I recently shot some HP5+ in the Otway Ranges (dark) at 100asa. Up to 4 minute exposures to counter reciprocity.

    I developed them at 5 minutes, down from my N of 10 minutes. Turned out fine.

    If you're really that worried and/or they're that important, perhaps shoot some more HP5+ at the same exposure and run some test times?
     
  13. PeterB

    PeterB Subscriber

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    LJH and heterolysis thanks for your feedback and ideas. And Mark yes I will test if I don't feel comfortable with my plan to dev for N-1.
     
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  15. David Allen

    David Allen Member

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    Hi Peter,

    My recommendation would be to not do a N-1 development but rather use a two-bath developer - such as Barry Thornton's. The two-bath developer will ensure that your highlights do not blow out and that the mid-tones will retain their normal contrast. You will probably need to print for longer but you will find that in 'printing down' down the negatives, the lower mid-tones and upper shadows will have more 'sparkle' or vibrancy of detail than you normally get. If you do a N-1 development you cannot be sure that this will bring the highlights down enough and will give you flatter negatives which you will then have to print on a harder grade of paper.

    Also, several people have advised you that overexposure produces more grain. This a very long standing photographic old wives tale (been around since, at least, when Victor Blackman used to write a column in the UK's Amateur Photographer magazine), often repeated and passed on to subsequent generations without anyone really thinking it through logically. To explain:

    a) On every negative that has ever made, you will have a range of tones from the shadows to the highlights. If it was a bright sunny day you will have at least 8 stops difference between the deep shadow to brightest highlight. This effectively means that the highlights have received 8 stops more exposure (i.e 'overexposed' by more than 8 stops) than the shadows. Are your highlights grainier than your mid-tone/shadows? If the concept that overexposure caused grain was correct, all of our photographs should have grainer highlights in comparison to the mid-tones/shadows - which simply is not the case. Where grain is the most noticeable in the print (especially in B&W) is in areas with a lot of brighter mid-tones (such as a blue sky, etc). This is simply because this tone is where we optically notice it more.

    b) Those of us who test for our own personal Exposure Index (EI) all achieve differing results in accordance with our own preferences. In reality that means that, where I use an EI of 200 for Delta 400 processed in my choice of developer and a friend of mine, Johann, chooses to shoot Delta 400 at an EI of 400. Therefore, my films are 'overexposed' in comparison to his films and, according to folklore, my images should be grainier than his. In reality my images are far finer grained than his. The reason is that Johann likes noticeable grain. The real difference between our negatives is that he doesn't care about detail in the deep shadows and he uses HC110 dilution A with vigorous agitation..

    The key thing with how grain appears in the final print is that it is affected by:

    Type/speed of the film's emulsion
    Type of developer used
    Temperature of the developer
    Time of development
    Agitation method
    Print developer
    Grade of paper used

    In conclusion, if you use a N-1 development you will not be sure of saving your highlights BUT you can be very sure that you will lower the film's overall contrast which will result in you needing to print on a harder grade of paper that will accentuate the appearance of grain (hence the cause of this misunderstanding that overexposure causes grain) and potentially make it harder to achieve a pleasing balance should you need to undertake dodging and burning (always trickier to get correct at higher grades).

    As other have advised, the best would be to shoot a test roll with the same degree of overexposure with a scene that has similar contrast range to your important (as yet undeveloped) films and process it in a two-bath developer. I think that you will be very pleasantly surprised at the results.

    Sorry this post ended up being so long and best luck with rescuing your important films.

    Bests,

    David
    www.dsallen.de
     
  16. michael_r

    michael_r Subscriber

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    Peter, as Mark says you're overcomplicating it, and you're also confusing developed density ranges with exposure ranges.

    Think of it this way if you want to be on the straight line: If the exposure range (x-axis on the H&D graph) of the straight line defines your lattitude, reducing development cannot lengthen it. It can either maintain it with a reduced slope, or shorten it due to increasing compression in the low and high values. As you decrease development, the straight line portion of the curve will tend to shorten. The toe gets longer and the shoulder gets longer. The shoulder (where highlight contrast begins to compress) is reached sooner.

    Another way to think about it in Zone System terms: You placed your shadows on Zone II and highlights on Zone VIII. We assume you thought you were placing that entire range on the straight line. You then overexposed the film 4 stops. This simply means you moved everything to the right by 4 stops or a relative log-H of 1.2. Your Zone VIII now falls on Zone XII. But the curve is still a straight line at Zone XII (as it should be). So the difference between your shadows and highlights doesn't change. All the values will increase in density by the same amount. You just have a denser negative - which means more graininess, and longer printing times.

    Of course this all assumes your normal contrast is the same as Ilford's. As I said before, N-1 is a relatively mild contraction and should not cause too much shortening of the straight line, but at best you gain nothing.

    The only thing you gain by reducing development is slightly reduced graininess which can slightly offset the inherent increase in graininess resulting from overexposure.

    This is one of the most common mistakes people make with the Zone System. You cannot selectively move highlights down the normal curve by reducing development. There is no free lunch. Reducing development compresses contrast by altering the overall slope and/or the shape of the curve.
     
    Last edited by a moderator: May 27, 2013
  17. markbarendt

    markbarendt Subscriber

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    This is also why I don't use reduced development. Extra exposure in the camera for me simply means extra exposure in the enlarger. Nothing more, nothing less. Mistakes in camera exposure simply can't be made "normal" by adjusting development, the damage is done when the shutter fires.

    The math involved here is a hard task master.

    For example those above who are suggesting a staining or two bath developer to "hold the highlights" are essentially suggesting modifying the shoulder to compress the highlight detail. Yes surely more detail may straight print inside the papers range but the top of the film curve has to flatten out to get you that effect. Conversely a "normal" non-compensating developer lets the film curve run out straight(er), the highlights may require burning to get them inside the papers print range, but greater local contrast is available.

    Like Michael said, there's no free lunch.
     
  18. michael_r

    michael_r Subscriber

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    I agree with what Mark is saying here.

    Minus development can help make printing easier when the scene luminance range exceeds normal, but that is not the case in Peter's situation. He doesn't have subject contrast issue, simply an overexposure issue.

    If we were in the same room it would be pretty straight forward to demonstrate on a curve without math. You can't "correct" for overexposure with reduced development without reducing total and local contrast.
     
  19. MattKing

    MattKing Subscriber

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    I'd suggest developing the film normally in whatever developer you use that gives the least amount of speed enhancement.

    Ilford Perceptol?
     
  20. jnanian

    jnanian Advertiser Advertiser

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    stand develop your film in caffenol C 25-30mins it will look completely normal
     
  21. PeterB

    PeterB Subscriber

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    OK folks, I now have pictorially constructed what I was trying to explain above. I have used Kodak's published characteristic curves for TRI-X 400 as my example (Ilford doesn't publish the same data for HP5). I suggest that if one sufficiently overexposes an image then there is a greater compression of highlight tones if one develops for longer (see the following image). I hope this counters claims to the contrary.

    Greater highlight compression with longer development times for overexposed images.png

    Of course the overall image contrast will reduce but that is the trade-off which can be corrected for with a higher grade paper/MG filter.

    Therefore if I go from N to N-1 development, any highlight compression should be reduced.

    regards
    Peter
     
  22. markbarendt

    markbarendt Subscriber

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    image.jpg

    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.

    image.jpg

    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/forum216/69617-shaping-tone-curve-rodinal-negative.html
     
    Last edited by a moderator: May 28, 2013
  23. michael_r

    michael_r Subscriber

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    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.
     
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  24. sun of sand

    sun of sand Member

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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
     
  25. PeterB

    PeterB Subscriber

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    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
     
  26. michael_r

    michael_r Subscriber

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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.
     
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