ISO100 vs 400 and exposing one as the other.

Discussion in 'Beyond the Basics' started by Garbz, Jan 4, 2006.

  1. Garbz

    Garbz No longer a newbie, moving up!

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    Last time we were in the city taking night shots I started off using ISO400 film since there was an unfinished roll left in the camera. As soon as that one was finished I put the ISO100 roll in. The differences were amazing. On the ISO100 the sky was visible, and I mean visible as in wonderfull medium lit orange clouds which didn't show up at all on the ISO400 film. Everything else in the image is just as bright and the clouds were always there, they didn't blow in while I changed film.

    ISO400 film has an exposure lattitude of -1 +3 so I should be able to expose it as ISO100 or even ISO50. Will an ISO400 exposed as ISO100 look identical? I'm talking not only about the finer grain, but also the details I menioned above. The reason I ask is because I get free ISO400 film at the lab, but not ISO100.

    I'll try and post comparison pictures as soon as we get our main computer up and running again. (hopefully tonight)
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Well, the best way to find out would be to experiment and see for yourself. Night shots can be funny because of the long exposures.

    With longer exposures, you run into Reciprocity failure....and ISO 100 film may actually be more sensitive than ISO 400 in some situations.
     
  3. Garbz

    Garbz No longer a newbie, moving up!

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    well what got me is that the lights look like they are exposed roughly the same. As in the differences in the lights are so incredibly slight that the exposure times look the same for each shot (well 1/4 the time for the ISO100), but the sky:

    [​IMG]
     
  4. Rob

    Rob TPF Noob!

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    Theoretically this won't work, as the failure is based on the emulsions' need for a different exposure. However, actually, it might work as you will be changing the exposure and there's a very small chance that overexposure might solve the problem. I doubt it, I think it'll be worse!

    Rob
     
  5. Boltthrower

    Boltthrower TPF Noob!

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    I used to work at a lab people would shoot 400 @ 100 on accident and everything would be Blasted and washed out.... It was a lot of work to correct it...

    If you are going to bump it a little i wouldn't suggest going below 200 and if you are going to bump the ISO on it Please be nice and warn the lab tech :)
     
  6. Garbz

    Garbz No longer a newbie, moving up!

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    yeah I made the opposite mistake last week. I did a -1 compensation for my flash and forgot to set it back. Shot 3 rolls of ISO400 at ISO800 and where my camera metred for ISO800 correctly the lab compensated with no problem.

    I was just wondering because of the massive differences between ISO400 and ISO100 as posted above. I have since gotten 5 rolls of ISO100 for cheap so next time I need the dynamic range seen above i'll simply throw in that film.

    Boltthrower I have a question if it comes out washed out then why is it that the fujifilm Superia ISO400 has an exposure latitude of +3 according to the DX coding?

    /Edit DX coding not RX coding, Been playing with networks too long.
     

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