Changing ISO of film

Discussion in 'Exposure Discussion' started by pacoev, May 11, 2010.

  1. pacoev

    pacoev Member

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    Hi, I started taking photos with a canon at-1 and I did put a 400 ISO film, but I set 100 ISO in the camera propeties. What happen if I change the ISO about 100 to 400, does the film will ruin? Or should I keep the 100 ISO?
     
  2. Darkroom317

    Darkroom317 Member

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    Is this B&W or color? Are you developing it yourself?
     
  3. keithwms

    keithwms Member

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    You may as well stay with the choice you had for the rest of your roll. Just tell the developer to pull one stop (pulling two is probably unnecessary, I think). It'll be overexposed but probably fine. Print films can handle one or two stops of overexposure.

    P.S. I assume that you are talking about print film, not slide film, right?
     
  4. andrewkirkby

    andrewkirkby Member

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    Which film were you using?

    Some films behave quite well under pull processing and this is a technique often used in motion picture to increase contrast.
     
  5. pacoev

    pacoev Member

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    Thank you for all your replies. I did change the iso from 100 to 400, hope the film dont get ruin. Im really new in this, Im experimenting and thats a nice way to learn things. The film is a kodak 400/27 color film. Im dying to see the final results I feel very excited.
     
  6. Existing Light

    Existing Light Member

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    one time in a studio photography class, I shot a half of a roll of portra 400 at 100. I changed the aperture of the camera to get the correct exposure as soon as I noticed it. When I got the film developed, I couldnt tell a difference in the prints. I'm sure the lab adjusted the overexposed prints using a method not suitable for discussion here :D


    Your film should be fine. At the very least, you'll have plenty of shadow detail in the overexposed negatives :smile:

    Dont worry about it too much. I tend to overlook something simple like that at least one or two rolls a month :D
     
  7. pacoev

    pacoev Member

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    thank you, I was worried. do you always feel excited to see your pictures? It's my first time taking pictures and Im very excited :D
     
  8. Existing Light

    Existing Light Member

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    I just finished reversal processing a roll of FP4+ film (processing the B&W negatives as slides), and I was excited/anxious about seeing the slides, especially during the final wash. I just started reversal processing a few weeks ago, so I'm new to it. Taking them out of the wash to dry still feels like when I processed my first B&W negtives a few years ago. It's very exciting to look at them in front of the light when I take them off the reel. I cant wait for them to dry so I can mount and project them :D

    Good luck with your roll. I hope it turns out fine (I'm sure it will) :D
     
  9. pacoev

    pacoev Member

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    Thank you! I will try to show some shoots. :smile:
     
  10. Galah

    Galah Member

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    as far as I understand it (from the theory only), the ISO of a given film is "indicative" only: all things being perfect, it will result in a negative placed around the average or "mid-gray" point on the film's characteristic curve (or density range).

    Using the film as if it were rated higher ("increasing" the nominal ISO or "pushing" the film) results in the negative densities migrating towards the toe of the films characteristic curve: i.e. a loss of shadow detail. This can be "restored" to some extent, by increasing the time the film is in the developer (or using a more active developer). This used to be a relatively common practice among professionals and keen amateurs.

    Using the film as if it were rated lower (pulling it) results in the densities migrating to the "shoulder" or upper end of the film's density range, giving "blown" highlights and well exposed/overexposed shadows. The film may be treated by reducing the time spent in the developer. Unfortunately, truly blown highlights will probably be blank and unrecoverable.

    In both cases, there are, also, corresponding actions to be taken in the Printing stage (with B&W or colour negative film)

    In either case, the colour balance is likely to be affected in unexpected ways (colours not true to life), as a large variation from "normal" exposure will affect the film's colour layers differentially.

    If developing the film yourself, the thing to do is to expose the film using the same ISO setting throughout, then you can deal with it uniformly in development (or tell your lab the problem and they can deal with it). If you realize you have made an ISO setting error and change halfway through the film, you get the worst of both worlds:tongue:.

    I expect, in your case, you overexposed (at least some) of your film by 2 stops. This would "blow" your highlights, give you well to overexposed shadows and result in washed-out (pastel) colour rendition. :smile:

    Colour negative film has a greater tolerance for exposure divergence from the norm than does colour reversal (slide) film.
     
    Last edited by a moderator: May 12, 2010
  11. 2F/2F

    2F/2F Member

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    Your film has no ISO. The ISO is an organization, not a description of your film. They determine the standards for how a film's speed is defined and determined, as well as numerous other international standards. So, ISO film speed is set in stone, because it has the "ISO" attached to it. Since they name their criteria and processes that determine a film's speed, when you change these things or use different criteria, you no longer call it "ISO" film speed.

    Re rating your film changes only one thing: exposure. Since a film rating is simply an input into your cameras exposure meter, changing this could not possibly change the actual sensitivity of the film; only what the meter does. So, since your camera thought you were using 100 film, but your film's speed is actually 400 ISO, your film is two stops more exposed than it would have been if you had set the meter at 400. Since it is negative film, it will be ok, though you may want to underdevelop the film 20 to 30 percent to make it easier to print.
     
    Last edited by a moderator: May 12, 2010