Film Speed??? Boy am I confused!

Discussion in 'B&W: Film, Paper, Chemistry' started by BWGirl, Jul 3, 2004.

  1. BWGirl

    BWGirl Member

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    Hi!
    I am reading a few books on photography and I just cannot get something through my head...
    I keep seeing things about 'pushing' and 'pulling' film and it seems that every explanation is just a bit beyond where I am...like all the authors have so much knowledge that you cannot even conceive that someone needs to start at ground zero! :confused:
    I use Ilford Delta 100. I develop my film in Ilfosol-S and Ilford Rapid Fixer. Same with the prints (but use developer for paper there).
    Here are my questions...
    1. Why would I change the speed of the film when I put it in the camera...like setting the ISO to some other number?
    2. Would I make it higher or lower?
    3. How would making the change to the film affect developing the film? Like if I currently develop for 6 minutes, would I still do that, or pick a time that corresponds to whatever I set the ISO number to on my camera?
    4. What would I expect to see on my prints as a result of this?

    So, as you can see I am really not understanding this concept and I'd really like to! So thanks in advance for any help you can give me!
    Jeanette
     
  2. jim kirk jr.

    jim kirk jr. Member

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    Hey Jeanette,
    Hope I can help.You push film to gain extra filmm speed,ie-setting your 100 sped film to 200,400,800,1600 in low light conditions(since your using a slow film this applies)pulling film reduces speed of film,ie-setting your ISO in you case to 50,25,etc in bright light conditions which your current film sped should be okay.when you push film you need toincrease dev. times by by 20percent for each one stop increase in exposure and conversely you decrease by 20 percentif you pulled your film.the best way to avoid having to increase or decrease dev. times is to bracket your exposures,ie-along with the meter reading go one above and under therebye making three exposures for each shot.in terms of making your ISO different than what its dx coded for(100 speed)
    depending on your camera there should be an ISO marking on a dial somewhere andwhen turned on usually you cange it by turning the dial used for shutter speed but check your manual
     
  3. jim kirk jr.

    jim kirk jr. Member

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    almost forgot,pushing film will generally result in a loss of shadow detail with more contrast and pulling will reduce the contrast and give more detail to shadow areas.my suggestion is to always bracket and keep dev. times the same.

    Jim
     
  4. Ole

    Ole Moderator Staff Member Moderator

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    Because you really need a faster film - because the light is poor, for instance. Or because you need a slower film - to smoothen flowing water, or something like that. Or maybe you just don't believe what the manufacturer has put on the packet.

    Pushing is higher (you push it up), pulling is lower (you pull it down)

    When pushing you generally increase development, when pulling you decrease it. Not quite corresponding to what you set the ISO number to; Delta 100 doesn't miraculously turn into Delta 400 because you set the camera to ISO 400. Off the top of my head (which I'm sure someone is going to bite off in a moment) you increase by 20% for each stop you push, decrease by 15% for each stop you pull. Shooting ISO 100 film at ISO 200 is one stop push, shooting ISO 100 flim as ISO 50 is one stop pull.

    When pushing film you can expect deep, empty shadow areas, and exessive contrast in midtones and highlights. When pulling you can expect good shadow definition, but very "flat" negatives and possibly burned-out highlights. But sometimes those effects can help make shots possible...
     
  5. Francesco

    Francesco Member

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    The manufacturer's rated film speed is based on lab conditions for scenes of normal brightness. It is when we deviate from these conditions that we need to change the effective film speed - i.e. we increase or decrease exposure and match development accordingly. In addition, we are also trying to match the negative to the end result - the paper we shall be using. The kind of paper we will be using also determines effective film speed. More variables, more confusion. Test, test, test! Eventually you will find yourself saying "One Scene, One Shot".
     
  6. gma

    gma Member

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    You certainly received answers from very experienced and accomplished photographers. I noticed that you shoot 35mm. That means that you will have to expose and develop the entire roll the same. In the event that you encounter a different situation halfway through you have to decide whether to load a new roll or compromise the previous shots. One of the obvious benefits of using LF is that you can expose and develop every sheet as you choose.

    On other threads I have noticed that some photographers use a lower EI than published for b&w film to gain more detail in the shadows.
     
  7. David R Munson

    David R Munson Member

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    For normal use, I essentially never expose anything outside of color transparency film at the manufacturer's stated ISO. I have found that I essentially cannot get an ideal negative out of a negative film at the stated ISO. Tri-X gets rated at 200, Bergger at 100, HP5 at 250, NPS at 100. You get the idea. Learning this was one of those things that did more to improve the technical quality of my images than most other things. For a long, long time I always shot at the stated ISO and not an EI that I arrived at myself through testing. Looking back, those negatives are thin and lack shadow detail.
     
  8. BWGirl

    BWGirl Member

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    Thanks everyone!

    I think I am understanding this a little better, now. I think I will experiment with my next roll. (Yeah, I can see how using roll film sort of limits what you can do from shot to shot since the whole toll must be developed at the same rate.

    Thanks again!
    Jeanette
     
  9. mark

    mark Member

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    When shooting roll film B/W I find that if I shoot for the highs and develope normally then I get some pretty good negatives. I found I like delta 100 at 100

    When shooting roll film I shoot the same combination you do. I really like how easy a combination it is. Try rating Delta 100 at 50 for one roll and shoot the same scene with anther roll at 100. Develope both normal. Contact them together so you can see the difference. You can do the same with a roll exposed at 200. This gives you one set of negs that are exposed with one extra stop of light the 50, one normal the 100, and one with less light the 200. See which makes a neg you like the most. Like I said I like it at 100. To each their own.
     
  10. gma

    gma Member

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    Jeanette,

    Personal experience is the best teacher. Mark's recommendation to test your usual 100 speed film using 50,100 and 200 sounds like a great idea. Rather than use three separate rolls, why not just meter for 100, shoot, then expose 1 stop more then 1 stop less on the same 36 exp roll. I think it will be well worth your time. You could read photo magazines for years and not learn as much as from this one simple experiment. I hope you will take his advise . If you do please report the results.

    gma
     
  11. Les McLean

    Les McLean Subscriber

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    Calculating your own film speed is not an easy task and bracketing as has been suggested here is certainly not the way to go. You are bound to get one exposure correct in the bracket but depending on the contrast range in the subject you are not certain to give the film the correct development. The factors that govern the quality of information on the negative are both exposure, which determines how much information you get in the shadows, and development which controls contrast and the density of the highlights. hence the old addage "expose for the shadows and develop for the highlights"

    The Zone System is one way to go but it can get complicated and is not necessarily the best way for 35mm or roll film. The subject of personal film speed is quite involved and too long to explain in simple terms here and I ask your indulgence, for I would suggest that you have a look at my book, Creative Black and White Photography where I have given a detailed, but relatively simple description of working out your own film speed and how to deal with extreme high or low contrast situations. Please forgive the plug for the book for I don't believe that members of photographic forums should use them for personal publicity.
     
  12. Shesh

    Shesh Member

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    I do not mean to step on Les's toes. One other website that has some information regarding this is Barry Thornton's website. http://www.barry-thornton.co.uk/pfs.htm refers to the task of finding your own film speed. Read this article after you read the article on the zone system on the same website.
     
  13. photomc

    photomc Member

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    There are actually several sites and many books that discuss personal film speed. Know because I went through this earlier this year, it is not hard to do, but requires preparation, attention to details and burning some film up on test shots. Les, I don't feel that you were plugging your book at all (keep looking for it, quess I will have to order it)..the whole concept of a personal EI is something some grasp and other do not - at leat right away.

    Since I do not have Les's book, I can't say if his explanation is easier than some of the ones I have seen...some become way to complicated. LooK around, find an explanation that makes sense to YOU and then go for it ...it is the basic building block for exposure/film development and printing.

    Good Luck..
     
  14. gma

    gma Member

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    Please excuse the long pause between replies. I was just looking over the comments again and I noticed that you use Ilford Delta 100 film. I think traditional grain films are better for pushing and pulling than the "T grain" emulsion films. Precise exposure and development are critical to obtain good negatives with the "T grain" films. Traditional emulsion films such as Ilford FP4 or HP5, Kodak Tri-X, J&C Classic 200 or 400, EFKE 100 or Foma 400 can be pushed and pulled easily for better and more consistent results in my opinion.
     
  15. gainer

    gainer Subscriber

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    The film speed that is appropriate for you depends on the shape of the characteristic curve, how you do your metering, and what you expect to see in a print. Bracketting exposures for a given test scene will show you how to develop when you shoot a scene with that same brightness range. Your tests for film speed thus should include a set of bracketted exposures for each of a set of scene brightness ranges.
     
  16. Helen B

    Helen B Member

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    Patrick's brief reply is the best explanation I have ever read - so complete, and only three sentences. The first sentence is a gem that should replace the inadequate 'Expose for the shadows, develop for the highlights'.

    Best,
    Helen
     
  17. harveyje

    harveyje Subscriber

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    One advantage of the chromogenic films (XP2, etc) is that you can expose at different exposure indices on the same roll and usually get good to satisfactory results. At 100 you get finer grain but less sharpness, at 800 you have better stopping ability for action but slightly increased grain, etc. These films print very similar to conventional films.
     
  18. Juraj Kovacik

    Juraj Kovacik Subscriber

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    It is only my opinion, but I like Delta 100 at 100. It is a great film. I've used it at 200 and 50, but at 100 it fit me best. I develope it in ID 11, slightly, very very slightly below rewcomandet time. JK