How does one use unrated film?

Discussion in 'Alternative Techniques & Photo Gallery' started by Garbz, Oct 8, 2005.

  1. Garbz

    Garbz No longer a newbie, moving up!

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    Ok i'm not sure if this technically classes as alternative techniques but i guess i'll find out soon :)

    Last week I started with Infra red, this week it's Black and White, and i'm loving it all! The film i'm using atm is Kodak B&W 400, which is the most commonly available C-41 process film here. However a friend recomended a few others amongst them were:

    Kodak Portra 400BW
    Kodak T400CN
    and Ilford XP2

    It was interesting to hear that the Ilford and the T400CN is "unrated". Apparently it gives good results from ISO50 right up to ISO1600. And this simply doesn't make sense to me. Does this type of thing only apply in the Darkroom? I.e. If I were to develop these myself I could take a shot at ISO50 and ISO1600 and still get perfect shots?

    To me this makes no sense if sending things off to a lab where the film is thrown into a machine and it does the work? So here's my theory and can someone please tell me if this is right:

    1. Lower ISO = finer grain, Higher ISO = larger grain.
    2. Photos will need to be sent off to a pro photo lab and the lab will need to be informed at what ISO it was exposed at.
    3. The single film will all need to be shot at the same ISO to get consistent results.

    So have I hit the nail or am I so far out of the ballpark i'm playing a completely differnt sport?
     
  2. terri

    terri Administrator Staff Member Supporting Member

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    Hmmmm. Technically the points you make above are all correct. I think the recommendations you've read are simply to inform you that you can push or pull process the film. ? Strictly speaking, the film that says "400" is generally considered to be "rated 400", but that doesn't mean you can't push or pull process the stuff.

    And yes, you can't switch your ISO rating every other frame, or whatever, if you're going for consistency. Especially if you're pushing or pulling the film. Obviously we play with those ratings each time we use the exposure compensation wheel (if our cameras have one) but you do this knowing that, upon development, some of the frames will be processed spot on and some will fall where they may.

    Make any sense, or did I only manage to muddy it even more? ;)
     
  3. Hertz van Rental

    Hertz van Rental TPF Noob!

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    The films are actually rated at ISO400 but have a wide exposure latitude. The T400CN has a latitude of +4 and -2 stops, for example. Changing the ISO is just a way of telling your light meter that you want to under or over-expose your film.
    Compensation is done in development by over or under developing. C41 is colour processing so it doesn't work in quite the same way as 'traditional' B&W. For example, the image on the C41 neg contains no silver but is made up of dye formed as part of the processing.
    Like most things photographic the plus points are always balanced by the negatives, so which film you use tends to become just a matter of personal choice and what you are happiest using.
    Data sheet for XP2 can be downloaded as a PDF file here:
    www.ilford.com/html/us_english/pdf/XP2SGB_QX.pdf
    The Kodak site should have the data for their films. It's always advisable to read the data first.
     
  4. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Those are C41 process BW films. It's true; I've shot ISO 50 through 1600 on a single roll, and had it processed normally, and the shots were all printable. ISO 100 through 800 looked pretty good. It seems to me that it gets grainier at ISO 100 than at 200 or 400. I don't use it often, but it is very handy if you are going to be shooting both inside and outside on the same rolls; I like it at 200 in the sun, and 800 indoors.

    The flipside is that you lose a lot of the contrast control and tonal adjustments you get with traditional process BW films.
     
  5. Garbz

    Garbz No longer a newbie, moving up!

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    interesting that kinda contradicts what terry was saying, but then also makes sense to a degree :S

    Now i'm confused :) Maybe i'll just stick with ISO400 and let the lab do things as per their standard.
     
  6. terri

    terri Administrator Staff Member Supporting Member

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    No, I think we're all saying the same thing. It's just terminology. You were told, or read, that the films you mentioned were "not rated" and we are all saying that a film with "400" in its name is basically a 400 rated film (as opposed to, say, Kodak HIE, which really and truly is an unrated film).

    That said, that doesn't mean it can't be rated as low as 50, like ksmattfish has done, or as high as 1600, and processed normally with printable results. You just have to know your way around a darkroom, because you'll be dealing with a wide array of negative densities.

    But until you feel comfortable using it, you might indeed be happy with the results you get rating it 400 and sticking to that. :)
     
  7. Garbz

    Garbz No longer a newbie, moving up!

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    So we're back to the darkroom now. In the end I just ignore it and expose at ISO400 and send it to the lab, and if I do get into a situation where I need to expose higher or lower do the entire roll and let the lab know of the changes?
     
  8. terri

    terri Administrator Staff Member Supporting Member

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    Absolutely! If you send in a 400 rated film you've pushed or pulled, without letting them know, you'll be one sad little jack-o-lantern, cause they'll just process it normally. Always make sure you say it twice. ;)
     

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