Question about exposure time while multi-grade printing with filters

Discussion in 'Enlarging' started by BetterSense, Feb 25, 2009.

  1. BetterSense

    BetterSense Member

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    Certain multigrade filters claim an invariant exposure time between grades, or they provide a factor to calculate the new exposure time at the new contrast grades. Assume this works as it is supposed to.

    So I make a test print. If my blacks are both too grey, and my whites are too grey, I suppose you can switch to the next-highest contrast grade and use the same exposure.

    Now, suppose I make a print that needs more contrast. I find that the blacks are black enough, but the whites are grey. I switch to the next higher contrast grade. Should I change my exposure?

    Suppose my current print has fine whites, but the blacks are too grey. I could increase my exposure to make the blacks blacker, but suppose I judge that that would wash out my highlights. I changed to the next highest contrast grade. Should I change my exposure in this case?
     
  2. MattKing

    MattKing Subscriber

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    Bettersense:

    This may be why I've been enjoying the switch to split filter printing :smile:.

    The constant (invariant) exposure time between grades probably really only applies to the mid-tones.

    Usually what I do is try to arrive at a contrast and exposure time that works well with those mid-tones.

    Once I get those mid-tones coming out the way I want them, then and only then do I consider what burns or dodges I need to get the highlights and shadows where I want them. I may or may not be be adjusting the contrast filters for those burns and dodges.

    For most negatives, the burns and dodges are fairly minor, and frequently don't require any contrast adjustment. For particularly difficult negatives, the printing process can be quite complex.

    As you are new to this, I'd suggest starting out with some of the easier negatives. Look for even lighting (preferably somewhat diffused even lighting). As you gain experience, you can move to the tougher negatives, and not be as likely to get frustrated.

    One thing to remember. While a nice long range from deepest black shadows to sparkling white highlights is always impressive in a print, it is rarely mandatory, and sometimes it isn't even good.

    Good luck, and have fun!

    Matt
     
  3. Blighty

    Blighty Subscriber

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    As I understand it, this equal exposure between G.00 and G.3.5 relates only to midtones. Until or unless you start split-grade printing, it might be a better idea to get the highlights as you need them and bump up the contrast incrementally 'til you've got the dark tones you require, adjusting for exposure as necessary (you can do it the other way round if it's easier).
     
  4. bsdunek

    bsdunek Subscriber

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    I'm glad you said that, Matt. I think sometimes we make printing a technical exercise instead of an artistic one. I have seen many prints that have a really long tonal range, but, IMHO, are too dark and boding for the subject. Others, of course, are beautiful with the full range. Depends on the subject.
     
  5. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    To me, it isn't an 'either or' choice but striking a balance where I am comfortable and productive. Everybody has a different level where they like to operate.

    Photography is an art with a very high technical content. Crack open an optics textbook or a copy of Mees for a glimpse of the technology needed to place something in an "artiste's" (or hoi polloi) hands so that he need know no technology. Decrying 'too much technology' seems a bit silly.

    There are all sorts of non-artistic diversions in this hobby, gear acquisition stands out to my mind and I am guilty as any of having more stuff than I reasonably need. Some like nothing more than doing film tests. Using technology to quickly get to the visualized print with the least waste seems pretty sane to me.

    There aren't many who eschew light meters and do a five frame bracket for every shot. So why do the same in the darkroom? OTOH, sometimes bracketing is the solution.
     
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  6. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    Yes, and just which mid-tone it relates to changes when you change the paper you are using. Papers have an equal exposure point between 0.7 to 1.2 OD, (ZV/18% to ZIV-III/shadows), and some are more equal than others.
     
  7. blaze-on

    blaze-on Member

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    I tend to add about 10% exp. time for each half grade I dial in.
     
  8. Maris

    Maris Member

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    The variable contrast filter set I use goes from a grade of -1 (very soft) to 5+ (very hard) in 1/2 step increments. The exposures stay the same for all filters from -1 to 3 1/2 and need to be doubled for the range from 4 to 5+.

    The question is what does the term "exposure" refer to; the exposure for the darks, the mid-tones or the highlights? With my filter set the key exposure, the one that stays the same, is the one for the highlights.

    I do test strips until I get the highlights right. That determines the number of seconds set on the enlarger timer. If the shadows are too grey I need to select a higher contrast filter; if too black a lower grade filter.

    The alternative, pegging exposure for the mid tones is too hard because changing the contrast grade shifts two things simultaneously; the highlights and the shadows! I find it less frustrating to have one thing that stays the same while the other thing is changed up or down.
     
  9. BetterSense

    BetterSense Member

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    Excellent. Which filter set and what paper do you use?
     
  10. tiberiustibz

    tiberiustibz Member

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    The filters are sensitromadensitycorrected so that all filters between 00 and 3.5 require the same exposure and 4-5 require double that. You may have to adjust when moving up in contrast if you didn't nail the midtones in the middle of the curve on your lower contrast print.
     
  11. CPorter

    CPorter Member

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    There's way's to test the speed matching (i.e., the ability to change contrast filters and still use the same printing exposure time) claims made by manufacturers. If you care to take it that far, then I would suggest Steve Anchell's The Variable Contrast Printing Manual; I believe all you'll need is a 21-step density tablet. There's also a good section in there about split grade printing; single filter printing, and multiple filter printing.
     
  12. Photo Engineer

    Photo Engineer Subscriber

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    One thing not mentioned here is that there are two ways to design a VC paper. One can take advantage of being rather invariant to printing filter(s) particularly in the mid tones. But, another method of making a VC paper gives vastly different speeds at each contrast grade.

    The first method is more difficult than the second and therefore, you will find that top grade papers are close to being invariant with a small filter factor, but papers from 3rd tier manufacturers may vary by several stops as contrast grade varies.

    This will generally be the case with graded papers from the same companies.

    The reason is that top grade companies will design an emulsion for each grade and tailor the speeds to match, but 3rd tier companies with less R&D money will opt to use 1 emulsion and force fit contrast allowing speed to wander all over. Generally, speed goes up with contrast in these cases.

    So, result also depends on paper.

    PE
     
  13. BetterSense

    BetterSense Member

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    Wonderful information. Thank you everybody.
     
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  15. Mahler_one

    Mahler_one Member

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    Of course, you might consider doing you own tests to define the "speeds" of your own filters-either in sets, or individually. Steve Anchell's book gives good instructions for making such determinations without the use of a densitometer, and Ralph Lambrecht in his legendary and encylopedic Way Beyond Monochrome also presents a bit more technical approach to making such "filter speed" determinations. I also believe that Nicholas presents, on his web site ( Darkroom Automation ), detailed instructions for making " tone test strips" ( my words, not his )so that various tones can be easily obtained with each grade with each paper you use. There are methods to proceed should you desire, and have both the inclination and time.

    OTOH, I believe that Maris and blightly make an excellent point, and their method is the way I am currently working as well. It is the "method" taught in the wonderful book by Carson Graves. It should be pointed out, of course, that when one changes grades of paper so that the blacks are "correct", that the exposure for the highlights also changes. However, you tell us that your filter set is speed matched for the highlights, and so such highlight exposure changes are not likely to be difficult to find. Note that if the highlights and the shadows are to your liking that the intermediate tones will "fall into place" ( as explained by Mr. Graves ).
     
    Last edited by a moderator: Feb 26, 2009
  16. Mahler_one

    Mahler_one Member

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    Thus, if I might, let's consider one of your questions:

    <Suppose my current print has fine whites, but the blacks are too grey. I could increase my exposure to make the blacks blacker, but suppose I judge that that would wash out my highlights. I changed to the next highest contrast grade. Should I change my exposure in this case?>

    In the scenario envisioned by some of us, and as taught by Carson Graves, if the blacks are too grey you do not increase your exposure to make the blacks darker. As you suspected, you then reach for your filter set, and increase the contrast which will make the shadows to your liking. As Mr. Graves has taught and written, the other intermediate tones will fall into place. Since your filters are speed matched for the highlights, your exposure for the highlights will be correct. If for some reason the highlights are NOT correctly exposed, then small changes in the highlight exposure should be considered. In the scenario we espouse, always expose first for the most important highlights, then examine the print. Modify the contrast based upon the shadows....too black, decrease the contrast grade; too grey, increase the contrast grade. The nice thing about VC papers is that the contrast grades might be almost infinitely variable ( depending upon your filters, your paper, your developer ) by using small changes in the settings of your filters. Thus, you might be able to dial in a filter grade of 2 3/4 if 2 1/4 isn't to your liking and the shadows aren't quite right to your eyes. As needed, modify the exposure slighlty so that the highlights in each print are the same, or very similar to the highlights in your test strip, or first print. Those of us who like to experiment with graded paper can also try to find some intermediate grades, but we must use different developing times, or developers, or combinations of both ( ! ) in order to more finally tune the contrast we seek. Frankly, as I write about the subject, using VC paper appears to be much easier!

    I sincerely hope that we all have been of a little help to you, and I wish you much success in your endeavors.

    Ed
     
  17. Mahler_one

    Mahler_one Member

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    Great point, as usual, made by PE above. PE...how do you find all of this arcane information? So THAT'S why the exposure from about grade 1 to 3 on my brand name papers isn't all that different! Thanks.

    Ed
     
  18. Photo Engineer

    Photo Engineer Subscriber

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    My comments were based on actually making and coating the emulsions and papers. :D

    So, to me, it was not arcane. It was all in a days (paid) work.

    PE
     
  19. RalphLambrecht

    RalphLambrecht Member

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    Equal exposure time for filters aims for the paper's ISO speed point, which is at 0.6 plus b+f density. This is lighter than Zone V, which has a density of 0.75, but the whole idea of not changing the exposure time when changing contrast only works with calibrated enlarger setups anyway. And even then, it's safe to assume that exposure needs to be slightly adjusted after a contrast change.

    For most prints, I teststrip the exposure for the highlights and adjust the shadows with contrast. If you get significant highlights and shadows on one test strip, you can determine exposure and contrast in one go.
     
  20. RalphLambrecht

    RalphLambrecht Member

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    View attachment ExpCompCntrstChangeEd2.pdf
     
  21. RalphLambrecht

    RalphLambrecht Member

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  22. RalphLambrecht

    RalphLambrecht Member

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    exactly. rxpose for the highlights and correct the shadows with contrast.
     
  23. MattKing

    MattKing Subscriber

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    Thanks Ralph - another addition to my mini-library of Way Beyond Monochrome pdf excerpts :smile:.

    For when I want to read from the computer screen, rather than from my (version 1) book.
     
  24. tkamiya

    tkamiya Member

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    Here are my suggestions and reasoning behind each. This is what I would do in my own darkroom. Because of the way it was worded, I'm assuming OP's prints are reasonably close, not way off, from being good. Once I get my prints reasonably close to right and start perfecting it, more formalized process doesn't work for me.

    I'd use the next higher contrast grade and the same exposure timing to start. Tones below mid gray will move lighter and tones above mid gray will move darker - increasing contrast. Once I have the right contrast, then I'd re-evaluate the exposure timing.

    I'd use the higher contrast grade filter. Then reduce the exposure a bit. Otherwise, you'd start losing shadow details due to darker grays moving towards black.

    I'd use higher contrast grade, then increase the exposure timing. Otherwise, highlight detail will be lost.
     
  25. brian steinberger

    brian steinberger Subscriber

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    Constant exposure to me means the highlights are held constant as the filter is changed and the shadows become progressively darker. This is important because in printing we expose for the highlights and change contrast for the shadows.

    I find my highlight exposure by using a highlight test strip printer found in Ralph's book Way Beyond Monochrome. It produces a series of test strips of the same area of important highlight. Once the exposure is found for the highlight the contrast (filter) is changed to get the shadows where they need to be. Each time contrast is changed a new test strip is made as exposure usually does need changed unless it's a very small change. This is the method for single contrast printing.

    I've moved more toward split grade printing as mentioned by Matt. This is a much easier way to get to a finished exposure time and dodging and burning is much more effective this way as local contrast can be changed by burning and dodging during only one or both filter exposures.
     
  26. octofish

    octofish Member

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    Sorry to reopen an old thread, but it seems to fit here.

    I'm working towards making my process a lot more systematic to save on flailiing around with exposure and grade. I want to build up a table of exposure time multiplication factors against colour head filtration settings so I can move between grades easily without having to test strip at each grade. I've been trying to keep midtones constant but i'm finding it just too hard to be consistent.

    Most people seem to set the exposure for highlights first, and then modify shadow with contrast grade so figure I would do this too. But just for the sake of better understanding, why would you for instance not set your shadow exposure first, and modify highlights with contrast grade instead? These two approaches would give me different numbers would they not? Would both approaches work?

    Or am I missing something?