A bit confused about film speed...

Discussion in 'Exposure Discussion' started by Ishotharold, May 31, 2006.

  1. Ishotharold

    Ishotharold Member

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    Coming from digital (I'm sorry, I have seen the light in only 2 rolls and I apologize for my many digital sins over the past 2 years :wink:) I'm a bit confused about film speed, it seems much more subjective in metering, perhaps I am missing something but when I shot with my digis it was always set the ISO and meter for what its set. However I seem to be reading all kinds of stuff aobut people exposing at a different film speed then the listed, what is the reason for this? Is it coupled with expanding and contracting in development? I had thought that epanding and contracting delt only with contrast and though required slight exposure adjustment I dont think thats what this is. Is it simply finding what the "acctual speed is with your meter/lens/bellows etc.? Or is there something else I'm misisng? Any recomendations would be appreciated, I'm am working my way through AA series, finnsihed the camera and aobut halfway through the neg. In the appendix he tests for effective film speed (I think he uses a different term) but once that speed is found, is there still reason to shoot at a different speed (pushing and pulling in development would be one I suppose but if I have the light I need to get the exposure I want at the shutter I need would this ever be superior?) I guess I'm getting the feeling that film speed is mroe subjective in analog than in digital, is that true? If so why? Thanks for the help.
     
  2. Jim Jones

    Jim Jones Subscriber

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    The ISO speed of negative film is biased towards underexposure. For better shadow detail many of us shoot at an exposure index lower than the ISO speed. Negative film has more latitude than digital, so it can be more subjective. Most film makers say that the ISO is a starting point to be modified according to the photographer's preferences. By the time you've finished the AA series and applied that knowledge to practice, you should be able to confidently alter exposure and developing as situations require.
     
  3. Markok765

    Markok765 Member

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    Use the box speed and dev as normal, or rate at one stop lower and cut dev by 15%. i belive when you do this you get the tonal range compressed and it is flat. if you push you get higher contrast and you lose detail
     
  4. roteague

    roteague Member

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    Ishotharold, keep in the mind the two responses you have concern B&W film, color film is a different ballgame.
     
  5. Ishotharold

    Ishotharold Member

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    thanks for the quick responses guys, sounds like I'm not missing anything "too" major and I will learn for myself with time what my preference is. Guess I better buy and shoot lots more film to test with :-D.
     
  6. HerrBremerhaven

    HerrBremerhaven Member

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    Lots of people like to set the exposure slightly different than the speed on the box. Sometimes an image result can be more pleasing if slightly underexposed, or slightly overexposed. You have more room with colour negative films than with colour positive (transparency, or sometimes called slide). Even with transparency films, quite often you can find many films are fine within 1/2 stop of proper exposure.

    A separate issue is that some people have cameras that are not super precise on exposure settings. Then they might find that always setting the film speed lower/higher might work better for them.

    Outside of that is push or pull, terms you might see used in different ways. A very generalized way to look at this: say you have ISO 100 transparency film, and you set your camera to ISO 200, then you have the film processed as if it were ISO 200 film. What you would find in such a push situation would often be slightly higher contrast, at least with transparency films. Pull processing is done less often by some people, though in a very general sense you could expect slightly less contrast. You would notice more of this using colour transparency films; you could have this done with colour negative, though some labs don't do that, and you might not notice much difference.

    Now for B/W films, the only film I have ever had pull processed was TriX. I would set my exposure meter for ISO 200, shoot accordingly, then process the film as if it were ISO 200 film; resulting in a somewhat lesser contrast. I have more often push processed, especially films like Ilford Delta 3200 (B/W), Kodak P1600 (transparency), and Kodak E200 (transparency). The E200 is an odd film for this, since the pushis not linear, and much exposure compensation is needed for each step; though I have worked out settings and processing to 4 2/3 stops push.

    Anyway, hopefully I was not too oversimplifying things. This type of discussion could probably be much more technical in nature, especially with some films.

    Ciao!

    Gordon
     
  7. JBrunner

    JBrunner Moderator Staff Member Moderator

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    Transparency film is (or was) sometimes slightly underrated to increase color saturation, but I would defer to Robert on this point.

    With B&W
    To add to the confusion, you do not get box speed with some film/developer combinations. You could change the developing accordingly, but often you get better results by underrating speed for that particular combination. Also, a particularly thick negative for some printing methods is desireable,
    and film is sometimes rated with that result in mind.
     
  8. Roger Hicks

    Roger Hicks Member

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    Slide and digital speeds are determined with reference to the highlights, because if you over-expose you will get 'blown' highlights (lots of pure white, plus washed-out colours).

    Black and white speeds are determined with reference to the shadows, to be sure you get adequate shadow detail: it's quite hard to blow the highlights with negatives (mono or colour) though at the printing stage you may need to burn in to get the highlight detail you want from the denser parts of the negatives.

    Mono ISO speeds for the same ISO 400 film can run from ISO 200 or below in a fine grain developer to ISO 650 or even a little above in a speed increasing developer such as Ilford Microphen.

    There's a free module on ISO film speeds in the Photo School at www.rogerandfrances.com.

    Cheers,

    Roger
     
  9. Helen B

    Helen B Member

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    For colour negative film (and chromogenic B&W negative film - ie XP2 etc), which has lots of latitude, it is common practice to set the meter to one stop or more below the box speed. The graph below illustrates one of the main reasons. For colour negative film the graininess decreases with increasing exposure. This effect is most pronounced at the low end of the film's sensitivity.

    You can see the effect in the graph below. Exposure increases from left to right.

    Conventional (ie silver-image) B&W negative film behaves the other way round, so you may want to avoid overexposure - you may even want to sacrifice shadow detail in some cases.

    Best,
    Helen
     

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  10. noseoil

    noseoil Member

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    All good answers above. One test you can do might help quite a bit here. Use a roll of film and play with exposure. Do a series of three shots of each exposure. Do one under, one at and one over the box speed. You can use a full stop for this experiment and see what happens. Use the same method each time (this is called bracketing). I think you will find it an interesting experience and may decide that "box speed" is not always correct. This should give you a better understanding of exposure (one side of the print) as it relates to film.

    Looking forward to your posts about development in a little while! tim
     
  11. naturephoto1

    naturephoto1 Subscriber

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    Also, part of the benefit of bracketing an exposure is to make up for inaccuracy in film speed rating, as well as lighting conditions, and metering inaccuracies. With transparency material bracketing is normally done in 1/2 (though is possible in 1/3) stop increments while for negatives, due to their latitude it is not uncommon to bracket in 1 stop increments.

    However, to check the accuracy of meter (particularly in board camera meter) it is recommended to check exposures using transparency material. This will let you know the accuracy of the meter since transparency material has such a narrow latitude. Since negatives have such a wide latitude it is not recommended to test meter accuracy with negatives.

    Rich
     
  12. Ishotharold

    Ishotharold Member

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    Wow, lots of great info here, I have another question now brought about by this disscussion. What is the difference between pushing/pulling and expanding contracting? Is it simply a matter of degree and intent? As I understand they both are based on developing more or less.
     
  13. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    "Pushing" film in the way most people think about it is something of a delusion. Increasing development time will push up the highlights of negative film (B&W or color), but won't do much for the shadows, and film speed is related to the density of the shadows. To increase shadow detail with underexposed film is possible to a degree with compensating developers, speed developers like Microphen or Acufine, low-agitation development techniques, flashing, and there are a few more exotic methods like "hypering."

    Expansion and contraction more accurately describe what happens when one simply increases or decreases development time, producing a corresponding increase or decrease in contrast.
     
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  15. mark

    mark Member

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    SO tell the guy what that ball game is, robert.


    I assumed he was talking about BW because of his expansion and contraction comment. As far as I know there is no expansion or contraction in slide film development to control contrast. But I could be wrong.
     
  16. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    Pushing slide film does increase contrast, so it's possible to use it in a controlled way, if you make the right tests.

    In a simple way, for instance, I like to use Provia 100F pushed one stop in flat light to improve contrast. This isn't a very precise application of the Zone System, but given what slide film can do, it's enough for my purposes.

    With neg film and slide film, exposure is based usually on the thinnest part of the film--the shadows on neg film and highlights on reversal film. If you underexpose the shadows on neg film, you lose them, just as you lose the highlights with slide film if you overexpose.
     
  17. jnanian

    jnanian Advertiser Advertiser

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    i'd love to know too. i don't shoot much color compared to b/w ... so when i do i'd like to have a better idea of what i am doing ...

    -john
     
  18. Ishotharold

    Ishotharold Member

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    I was talking about black and white, I have a few rolls of velvia that were included with the camera, plan to shoot those in wisconsin next week on sunrise, sunset and other preaty things, but for the most part I'm going to stick to b&w untill I lear as much as I can from it. Plus development is much cheaper in our darkroom then to send of color to a lab.
     
  19. mark

    mark Member

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    SO did you shoot harold?:smile: It has already been a long day and I just noticed what your name said.
     
  20. Ishotharold

    Ishotharold Member

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    Well, Harold is what someone coined the first (and only come to think of it) mule deer I shot back in 2000, and it just sorta stuck. That was before I found cameras or I prbly woulda been too busy taking pictures to shoot one :wink:.
     
  21. roteague

    roteague Member

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    Your assumption was fine Mark, I noticed the first few remarks were about B&W film, but didn't state that. Someone new would not have known that. I found nothing to comment about any of the previous remarks, and while I don't shoot B&W often (20 sheets last year), I still follow the B&W world (I am reading a magazine reprint series on B&W printing at the moment).

    Color is a different ballgame - with transparencies - you don't use expansion or contraction to control how the image comes out, you do that through the use of split neutral density filters or other techniques. As Rich was explaining before, when shooting transparencies when bracketing it will generally be in 1/2 stop increments, occasionaly in 1/3 stops. Most of the time, I find that the use of a split neutral density filter will more than compensate for anything more than a 1/2 stop difference.

    I don't push/pull transparency film. When I shoot the newer Velvia or Provia emulsions, 100, 100F, I shoot them at the rated speed, 100. When shooting the older Velvia 50 emulsion, I may shoot it at 40, depending upon what subject matter I am shooting - I've found 50 to be about right when shooting along the ocean, but I'll drop to 40 when shooting in the forests, or desert scenes.
     
  22. djkloss

    djkloss Subscriber

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    I just finished my first film speed test using AA's "The Negative". I picked up a Kodak densitometer for free. It's not digital, but it works for a 'starter'. The more you know, the easier it gets...so keep reading and pick the test that you like. (Everyone has a different method). Since I'm using Rodinal, I also had to factor in the dilution...not to add more confusion...but it was nice having that control. I'm now anxiously awaiting my first 'good' negatives to dry from my shoot using my 'personal EI'. One of the reasons I wanted to test the film was because I had never tried this film before and I found so many differing view points on how to develop it. Times and development dilutions were all different depending on which website you got your information from and what you were trying to achieve. I ended up with a (Rodinal) 1:100 dilution for 20 minutes. I didn't see that listed anywhere. The tray development looks better than the tank so I'm wondering if the amount of working solution per number of sheets has a factor in it as well.

    I'm hoping by doing this testing that I will have fewer 'bad' negatives. I got a lot of helpful suggestions from a thread I started about testing and densitometers. This may be of interest to you if you don't have one.

    Good luck to you!

    Dorothy
     
  23. DBP

    DBP Member

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    I know I trimmed down this quote and took it out of context, but it seemed like a good answer to the usual question.

    As for the subject of the thread, if one is just getting started with film, it is probably a good idea not to get too carried away with the finer aspects of the zone system, personal film speeds, and such. Black and white print film (can't speak for Scala) is extremely forgiving, as is color print film. Slide films are more forgiving than we think. Somewhere around here I have an article written back in the 50s on the subject of slide film latitude (specifically Kodachrome - which was pretty much the only game in town). If memory serves - and I may try to find the article later - they concluded that one stop either way was pretty manageable and that two stops underexposure was not fatal. Hence the "expose for the highlights rule".

    Personally, I regularly shoot Kodachrome 64 in a 1950s Argus using the 'sunny 16' rule with decent results, despite no precision in any aspect of that. There was a wonderful article by Roger Hicks (I think) a while back that talked about the cumulative margins of error between film batch, meter, shutter, and aperture to make the point that a lot of the precision we think we are applying is spurious. So I would try to get comfortable with a small set of films first (one slow, one fast, such as Plus-X and Tri-X or FP4+ and HP5) and probably one developer (something widely used like D-76), shooting at rated speeds, working on getting uniform results from your processing technique, then expand and adjust from there once you have enough experience to be able to duplicate results.

    (Roger - please forgive if I have either misattributed or misconstrued the article.)
     
  24. Roger Hicks

    Roger Hicks Member

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    Dear DBP,

    How could I possibly complain when you called it 'wonderful'? I'd take the credit even if I hadn't written it...

    Actually, I did do an article like that for Amateur Photographer two or three years back, and I'd certainly second your advice NOT to get into the Zone System and so forth when you're starting out. The neg/pos process is very flexible, and many people who think they're being really precise are actually being saved by that flexibility.

    My own view is that apart from the naming of Zones (a work of genius), the big drawback to the Zone System is that until you are a reasonably experienced photographer with a modest knowledge of sensitometry, the Zone System is merely a system of rote testing, and once you have enough experience and knowledge of sensitometry, you don't really need the Zone System anyway.

    In other words, if the Zone System works for you, great, but if it doesn't, walk away without a backward look. I expand upon this view in a free module in the Photo School at www.rogerandfrances.com, 'Why we don't use the Zone System'.

    Cheers,

    Roger
     
  25. Ishotharold

    Ishotharold Member

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    For me the zone system really helped in theroy. It made me realize exactly what is going on as far as tonal values and how they relate. I'm a long way off from seeing the world in grey scale, but it made me think about it. However, in practice, I dont think I will goto the testing that he suggests. I'm more intrested in staying consistent and adjusting if a problem develops. Seem fair?
     
  26. JBrunner

    JBrunner Moderator Staff Member Moderator

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    I think that is extremely lucid. For me, many theories and methods only begin to make sense with practical experience, even though I learned about them early on. I don't know of many photographers who actually use the zone system dogmatically, but there are some. I think most "Zoners" use a personal variation or adaptation that fits their temperament and working style. My personal zone system is always undergoing a slow evolution, as my understanding and work evolves. Consistency is the most important foundation of exposure, then when you make a change, you can be more certain that the results are not a random combination, and you remain in control of your proccess. This simple thing can be hard to learn. It was, at least, for me. On the flip side, don't let the science stifle your creativity, it is only the means to an end, and the end is important. I have seen many technically perfect pictures that lack soul, when some not so perfect pictures scream with the passion of the maker. Technical perfection with heart and soul, now there is the Holy Grail.