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Thread: pushing film speed - a delusion?

  1. #1

    pushing film speed - a delusion?

    I posted this on another forum, but I think I will have more informative responses here:

    Is pushing a film beyond its true speed just a delusion?

    I, for one, suspect it is!

    An emulsion has a definite speed (with a certain developer and a certain time) and while it is true this speed can vary a bit with altered developing times, I do not think there can even be as much as one stop true speed change.

    For example, should you find Tri-x to actually have 400 speed, you really cannot push Tri-x to 800, and certainly not 1600 – all you are doing is underexposing and overdeveloping.

    What I said here concerns PLACING ZONE III PROPERLY using the exposure index you think will work.

    The zone III shadow detail will not be there – and shadow detail is what film speed is all about! And you certainly aren’t going to get a speed of 3200 out of Tri-x (based on shadow detail and usual 400 speed), I don’t give a damn what you do to the film!

    It seems only 35mm photographers use pushing – and maybe some medium formatters do too – but I have never heard the large format guys talk about doing this, and THEY would be the fellows who sure could use faster film! If this were truly a viable process, I guarantee they would use it and speak of it often.

    Now, I know you guys running around shooting high contrast, dimly lit scenes and pushing your film to outrageous speeds will SWEAR it works great.

    OK – if you are pleased with what you have, then that is good. But, I’ll bet your negatives are thin and very high contrast and even your minor shadows are as black as black can be…therefore, you REALLY ARE NOT gaining film speed. You are only underexposing and overdeveloping to get printable densities in the mid-tones and high values.

    Again, FILM SPEED depends on proper shadow values! It does take a certain amount of light to excite the emulsion – if the emulsion doesn’t get that minimum amount of light then there is no density when you develop.

    THERE MAY BE certain developers that actually give, say 800 speed, to Tri-X – but probably at some ‘cost’ such as increased grain or other unwanted effects.
    But that IS the speed in that developer, and I think there can really be no ‘pushing’ done to significantly alter this established speed.

    I realize that a very flat scene can be photographed using a higher exposure index and overdeveloping and yield a good negative (essentially N+ development) – BUT, this would necessitate placing zone III on IV or higher (and what you’ve done here is actually place it properly with the proper film speed!) - again, if the important shadow value is actually placed on zone III and you UNDEREXPOSE by using a higher than actual film speed, that shadow detail is not going to be there as it should.

    I’d be interested if anyone can tell us about actually pushing a stop or more and preserving the shadows (basing exposure on proper shadow value) and tonality of a scene – that is, a full range of zones.

    So, tell me about it. Set me right if I am wrong…

  2. #2
    bob carnie's Avatar
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    pushing film speed - a delusion?

    wcwiseman

    basically I think you are correct, though under certain lighting situations one is forced to Under Expose and Overdevelop, with the shawdow detail suffering in all cases.
    But with Lith printing for example with one shot developing, this is exactly the kind of negative that gives the best result, as well for solarization I like a negative that looks like this.
    To say that a negative should be perfect, to produce good prints I would not agree. Certain situations and applications deserve different film / developer combinations.
    It would be a very boring photographic world if all we tried to do was to get the most tones out of a negative.
    Joseph Sudek did pretty well with limited tones , and Anton Corjbin made brilliant prints with underexposed/overdeveloped negatives.

  3. #3
    Resident Heretic Bruce Watson's Avatar
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    pushing film speed - a delusion?

    I actually got 4x5 Tri-X up to EI 1000 once. I misread the data sheet and was seriously overdeveloping. When I read my Zone VIII density, it was up around 2.5. This didn't bother the scanner much, but the images looked seriously burnt, and the highlights were getting to be quite grainy.

    I eventually figured it out and calmed it down and ended up with an EI of 400, and a Zone VIII of 1.3 which is about where I wanted to be.

    So... my experience says you are basically correct. A given film has to have a given amount of photons to start forming a latent image. If you don't have the light, you don't have the latent image. Developer type and useage can vary this some, but not a large amount.

    Bruce Watson

  4. #4

    pushing film speed - a delusion?

    Doesn't everyone find Little Danny Smith amusing? He must be one cool character- so intellectual and full of pertinent information! I know we all appreciate his sharing with us...

    Oh, by the way, everyone - I've just looked at Kodak's web site concerning pushing film (Tri-x particularly) and they admit "a loss of shadow detail" - so that pretty much makes my original point. You can expose at a higher EI (Tri-x @ EI1600, for example) but it is not a true speed increase.

    It's just that I have seen so much about pushing that I wondered if it really did increase film speed.
    I was just asking for other peoples' experiences here - (not asking for unwarranted sarcasm) for not everything published by the manufacturers is correct and sometimes they leave out info because it doesn't suit their purposes.

    Per Kodak it looks like they acknowledge a possible two stop push for Tri-x but with loss of shadow detail. So, to my mind, that's not really "pushing"- It's faking it.

    Perhaps it's a matter of semantics - "pushing" should perhaps be defined as "underexposing and overdeveloping to obtain good printable densities, with a loss of shadow detail." Now, that would be more clear and accurate, without implying there is an actual film speed increase.

  5. #5

    pushing film speed - a delusion?

    In reply to the first post, you're saying that someone would be shooting high contrast dimly lit scenes and then pushing the film. I'd do actually just the opposite, initially place subjects on higher zones and then underdevelop. Especially with dimly lit scenes where you need to take the reciprocity characteristics into account, the shadows will require more reciprocity compensation than the highlights, which in night time city photography may well need no correction at all. The effect you see here will be an increase in contrast already, which according to your visualization may need compasating for in development or may not. The shadow detail is an important factor in determining the exposure, but I'd say a two stop push and the resulting contrast increase within the high and mid values would be also something I'd want to anticipate when exposing the film. To properly answer to your question, you'd of course need to just try it out with the film and developer combination you're using. This is actually quite easy but time consuming. I'm not sure about Tri-X, but at least with TMX a more than two stop push and pull are "possible" (I'd think you can always force a film darker overall, but get just dark fog). I've tried this out in Rodinal only so far. What you're trying to find out is how little light on a film can produce a latent image and how high values can be brought down to reveal separation by a certain developer, all in the range of creating an actually useful (printable) negative overall. Besides, in a negative there can be subtle values you can reveal in printing your eye can't see on the negative itself that easily. How much you can bring these out depends on the practical problems you'll face making the print. I don't find it really helpful to think in film speeds, because that often means you're trying to "correctly" expose a scene, with a single reading. It should be quite obvious there's more to thinking in terms of gray shades (all in b&w that is) then just placing one dark value right. You'll learn a lot quicker what your film is capable of if you think in terms of zones and make notes. When you make a bad negative, at least you've got the notes to prove it!

  6. #6

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    pushing film speed - a delusion?

    WC, the answer to your question in my experience is "yes, it is a delusion".

    I believe the speed of a film is four stops (Zone V) up from the Threshhold Exposure (Zone I) where exposure to light (and development) begins to produce density in the emulsion. I have never been able to move that point by extending development.

    My only caveat is that I have heard persistant talk over the last four decades that one or two developers exist which tend to give slightly more "speed". Perhaps a half stop or so. But I have never had time to try any of them.

    I think the root of the issue is that 35mm photojournalists don't seem to care as much about shadow detail as we do.

  7. #7

    pushing film speed - a delusion?

    This is a much overblown issue. First, there are developers that give a real increased speed when measured with the ISO standard technique. This is usually only good for a stop at most; I can get about EI 160 out of APX 100 in medium format using TFX-2 without sacrificing shadow detail. This is not pushing.

    Pushing is a technique that exists in a context, and that context is low light. Frequently the only options are either no photograph at all, or a photograph with little shadow detail. Simply exposing for longer doesn't work very well--perhaps you are taking candid photographs of people, as is a hobby of mine. My ability to handhold bottoms out at around 1/15th of a second, 1/8th of a second, but if my subject moves, there is a very good chance they will come out blurry at those speeds. We see the same thing as large format photographers in subject motion--breezes through the grass and the like. Accordingly in low light I must push film to take those photographs.

    These considerations are essentially irrelevant to modern day large format photographers. They were quite relevant back in the days when press photographers used Speed Graphics, for exactly the same reason they are relevant to a certain sort of 35mm photographer today.

    Also, it should be noted that a modest push need not sacrifice all shadow detail. This photograph was shot on a high speed film pushed one stop, and retains a surprising amount of shadow detail. I could not possibly have taken that image without pushing.

  8. #8
    Whatever David A. Goldfarb's Avatar
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    pushing film speed - a delusion?

    In general, I agree that "pushing" is a delusion, if one is just talking about extending development time or increasing developer temperature.

    But as mentioned above, you can increase real speed measured as shadow density to some extent (about a stop or two) with certain developers, like Acufine, Microphen, Diafine, Perfection XR-1, or with techniques like stand development or compensating development, pre-flashing, or with more exotic methods like gas hypering and such.

    I often use Tri-X or J&C Classic 400 in Acufine at EI 640 for handheld 4x5" and 5x7" work. I've gotten about twice that speed with XR-1, but the overall look is a bit flat for my taste (even after trying various tweaks). It would be good for night photography under urban lighting conditions where contrast is high. I think my next speed developer test will be RAF pyro, which was designed for aerial photography and is mentioned in Haist's _Modern Photographic Processing_.

  9. #9
    bob carnie's Avatar
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    pushing film speed - a delusion?

    wcwiseman

    a very practical test to see this is to do a Black and White Ring Around. Old Kodak manuals had the proceedure and I did this first year college in 73, and I have to admit it was way over my head at the time.
    Basically one must find out first what a normal exposed and developed neg should look like. Then a series of exposure + - should be done from the normal , enough unders and overs so that you can develop under normal and over each exposure situation. * I hope you get the idea*
    The original scene should include a grey card and be lit with normal lighting ratio , lets say 1:3 .
    Then you print all the negatives to a common balance as well as you can and the resulting prints mounted in a ring around the normal exposed normal developed print.
    You could do this with any film developer combination your heart desires and make the exposure +- in th 1 stop and 2 stop range, as well make your development in the +- 1 and 2 time variations.
    Normal agitation should be considered as the normal / normal .
    If I want to test a certain film developer , this is what I do so that I can see with my eyes final prints and how the different pushes and pulls work on imagery I am taking.
    Hope this makes sense.
    Basically you should end up with fifteen prints.

  10. #10

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    pushing film speed - a delusion?

    It's really very simple. Exposure determines shadow density, development determines contrast.

    With B/W film you only need to know two things about the scene - the contrast range, in stops, of the elements you want to have detail in, and which shadows to put at ZIII. Those two things tell you exactly how to expose and develop the film.

    "Pushing" B/W film by underexposing then overdeveloping doesn't change that, the only thing you gain is higher contrast and the ability to get something usable on film at higher shutter speed or aperture than the correct one. Which is fine, I do it all the time, but like you said the "speed" of the film hasn't changed at all.

    Chrome films and E6 is a whole different animal, though. For example, if you have a 5 stop scene and expose correctly you can overdevelop to lift shadows and midtones without affecting the highlights. Basically, you've reduced contrast and made it look brighter on the light table. But if you underexpose and then overdevelop, it starts working like B/W film - contrast increases, as does color saturation. If you're shooting a low contrast scene this can really help, but do it with a high contrast scene and you get in trouble really fast! As one example, in a "normal" 5 stop scene, I've found that rating Kodak E100G at 80 then overdeveloping 1/2 stop nets a well detailed ZIII and brighter midtones than 100/normal does, with little or no affect on the highlights.

    Again though, like you said, you haven't changed the "speed" of the film at all, you've only gotten something on film that would have otherwise not been there (or been blurry). E6, unfortunately, doesn't like to be pushed more than 1 stop or so before the colors shift in irrepairable ways.

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