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Thread: How much to push/pull

  1. #1

    How much to push/pull

    When I was reading on sheet processing I found out the the best way to "bracked" is to take two exposures, process one, see how it looks and then process the se cond with push/pull to get a "perfect" exposure. All this sounds good, I did tha t, but the question is, how do you know how much to push or pull. Let say the first sheet is slightly too dark. I obviously want to push. How much? Can u se use my spot meter somehow to meter the slide on the light box? For example, assuming I have a building in the shot and I want the wall A (dark) to look like wall B (not so dark), could I just meter both walls and push the processing wit h the difference?

  2. #2
    Kevin Kolosky
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    How much to push/pull

    Sorin

    I believe that "to push" means to develop longer than normal. You state that if your first negative was too dark you would want to push. I would think that if you have a "too dark" (dense?) negative, then you would want to do one of two things, either develop less or expose less.

    Don't forget, push processing has alot more influence on the high values (in the print, dense areas in the negative) whereas adequate exposure is critical for the low values (in the print, light areas in the negative).

    May I suggest this. Do a test to determine your working ISO. that would be found by making exposures of a black card in shade and finding out which gives you .10 density of negative base plus fog. Once you find your working ISO you can then do some tests to determine development time for zones 7 and 8 so that you can match your negatives to your paper. Then, once you get all of that done, you can do a test to see for yourself how much push processing you would require to move a zone 6 up to a zone 7 or a zone 8 , etc. or pull processing to move a zone 8 down to a zone 7. You need to get a foot on a rock before you start trying to push and pull. Kevin

  3. #3

    How much to push/pull

    I appologise, I should've been more specific. I shoot color slide film exclusivly.

  4. #4

    How much to push/pull

    I think the E6 process does not allow this kind of flexibility. Most of these ideas are strictly for b&w film (Zone System N+1, N-2 etc). They're not push/pull in the normal sense (ie a whole stop like ASA400 to 800), but are minor adjustments to developing times to compress or expand the contrast range of the negative. I know you can push or pull E6 film, as most pro labs will do it (for an extra charge). Check the data sheet for the film.

  5. #5

    How much to push/pull

    It's so obvious English is not my first language. I can hardly make myself understood. I know how to push/pull E6. I know how to correct a half a stop or a full stop or any number of stops for that matter. What I don't know is how to evaluate (when looking at a slide) how much is was over/under exposed. So, I'm looking at the one that I developed at the nominal ISO, I somehow (and this is the "how to" question) determin how much was (let say) underexposed, then I process the second sheet accordingly.

  6. #6

    How much to push/pull

    I think this is old advice, and I agree that it applies more to B&W negatives than to trannies. Modern tranny films are very good indeed, and so are modern exposure meters. If you take an INCIDENT (not reflected reading)you should not need to bracket either your exposures or your development. I never do. Incidentally, a little while ago I had to push process Provia 100 by 2 stops. My processing lab said that this was O.K. and they were right - it did not block up and the colours were fine. Contrast was slightly up, but nothing to worry about. As I see it, in theory the answer to your question of how you judge the transparency is that the exposure is correct if, assuming you are viewing them on a light box, detail is visible in both the darkest bits that are not actually black and the lightest bits that are not actually white. As the level of illumination between lightboxes varies so much you have to assess this on your own lightbox. If you are printing from the tranny then the same criteria applies, although of course there is some adjustment possible at the printing stage. So much for the theory, in practice tranny films have a very limited range compared to black and white or even to colour neg., and you often simply can't get detail at both ends. You just have to choose which is more important! Your English is fine - I just hope you can understand my answer!

  7. #7

    How much to push/pull

    Your English is fine, I re-read your question, I did not read it correctly (my fault, not yours). Unfortunately, I think the answer is experience. The only way to develop a way to measure what you want is to run a series of tests where you change the development in small amounts (maybe 5 or 10%) and record the density changes. If E6 behaves like B&W, you'll need to have frames with several values on each one, since the shadows don't expand as much as highlights, and highlights don't compress as much as shadows.

  8. #8
    Founder QT Luong's Avatar
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    How much to push/pull

    In theory, it seems that the method you suggest could work. In practice, I don't know of anybody who does that. Maybe the problem is a spot meter would not measure an area small enough.

    You end up by knowing how much you alter the processing of the second sheet by experience. What I suggest is that you ask the lab technician for his advice to begin. After you've seen the results a couple dozens of times, you'll be able to guess with good accuracy.

    A few tips: (a) to begin stick with either 1/2 or 1/3 of stops. (b) To determine the amount of push, look at the highlight areas (they can be tiny, hence a meter would be of no help), and compare them with the average tone to see how much push they can take without washing out. Since you don't push beyond +1.5 stops (results in excessive contrast and murky shadows), all you have is to decide between a few values. (c) Be careful with pulling. Film is more sensitive to pulling than to pushing. The contrast is seriously reduced, and for optimal results, you will try to avoid pulling beyond -0.5 stops. Think about that when you are exposing.

  9. #9
    Founder QT Luong's Avatar
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    How much to push/pull

    It also seems that with your suggested method the readings would be dependent on the brightess of your lightbox, not to mention problems due to its possibly non-uniform illumination. It's surprising how much of that is compensated by the brain. I measured a difference of 2 fstops across my Logan, yet to the eye it looks sort of OK.

  10. #10

    How much to push/pull

    Tuan, shouldn't the difference between the area be independent of the light intensity ? Assuming of course the light is constant across the light table. And if it's not, I guess I could move the sheet to measure above the same area or the lt.

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