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Thread: Probable Goof

  1. #1
    Foamer
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    Probable Goof

    Was shooting TMax ISO 400 today and put a yellow filter on my lens. Realizing that would darken my exposure -1 stop I decided to adjust ISO on my meter to compensate. I think of exposure in terms of left & right, i.e. going "right" from f8--f11--f16 etc. will darken, and going "right" 1/125---1/250---1/500 will also darken one stop each step. I think I goofed by thinking ISO 400---ISO 200---ISO 100 will lighten exposure. Actually I'm reducing sensitivity which darkens. I'm slightly dyslexic and I think I went the wrong way. What I did was thinking ISO 400 with a yellow filter is darkening exposure by one stop, so to compensate set ISO to ISO 200. I now think went the wrong way and am now TWO stops underexposed, i.e. effectively ISO 100 with no filter? That's beyond the one stop pull the Massive Dev Chart shows. SO, maybe if I develop for one stop push (ISO 200) I should at least get something I can decently scan?


    Kent in SD
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  2. #2
    Vaughn's Avatar
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    Re: Probable Goof

    No. If it is 400 ISO film and you set your camera at ISO 200, the camera's meter thinks it has slower film in it then it actually does, and thus will 'over-expose' the ISO 400 film by one stop.

    So with 400 ISOfilm , setting the ISO at 200 and using a yellow filter will give you roughly the same exposure as setting it at 400 and using no filter.

    If you set ISO at 100 on the camera and used a yellow filter, that's close enough, given the latitude of B&W film. Give it a little less development if you have highlights to worry about.
    "Landscapes exist in the material world yet soar in the realms of the spirit..." Tsung Ping, 5th Century China

  3. #3
    Drew Wiley
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    Re: Probable Goof

    I wouldn't try to "push" it. Just develop normally, or perhaps a minute less. A bit of overexposure won't hurt unless your highlights are really up there. But for all practical purposes, yellow filters do have a 1 EV filter factor with TMY 400 film, effectively making it 200 speed instead. So you should be on right on target unless you initially metered through the filter itself.

  4. #4

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    Re: Probable Goof

    Quote Originally Posted by Two23 View Post
    Was shooting TMax ISO 400 today and put a yellow filter on my lens. Realizing that would darken my exposure -1 stop I decided to adjust ISO on my meter to compensate. I think of exposure in terms of left & right, i.e. going "right" from f8--f11--f16 etc. will darken, and going "right" 1/125---1/250---1/500 will also darken one stop each step. I think I goofed by thinking ISO 400---ISO 200---ISO 100 will lighten exposure. Actually I'm reducing sensitivity which darkens.
    If you're confusing yourself as you're confusing me by thinking in terms of exposure as 'darkening' and 'lightening', I can very well imagine you're scratching your head most of the time when you're out photographing.

    Expose more, or expose less. Exposing more is exposing longer or through a larger physical aperture. Exposing less is exposing shorter or through a smaller physical aperture. Overexposing is exposing more, underexposing is exposing less. Notice how neatly the terms all align in a logical fashion.

    It all gets a bit skewed of course if you realize that a larger physical aperture is a smaller f/stop number, but this can be either memorized or simply reasoned by remembering that the f/stop number is a division of focal length and physical aperture size.

    So my recommendation would be to (1) develop the negative normally and (2) work on not confusing the crap out of yourself. The latter takes some practice and granted, it may not be feasible in all areas of life, but at least in photography it's fairly manageable.

  5. #5
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    Re: Probable Goof

    Quote Originally Posted by koraks View Post
    If you're confusing yourself as you're confusing me by thinking in terms of exposure as 'darkening' and 'lightening', I can very well imagine you're scratching your head most of the time when you're out photographing.

    Expose more, or expose less. Exposing more is exposing longer or through a larger physical aperture. Exposing less is exposing shorter or through a smaller physical aperture. Overexposing is exposing more, underexposing is exposing less. Notice how neatly the terms all align in a logical fashion.

    It all gets a bit skewed of course if you realize that a larger physical aperture is a smaller f/stop number, but this can be either memorized or simply reasoned by remembering that the f/stop number is a division of focal length and physical aperture size.

    So my recommendation would be to (1) develop the negative normally and (2) work on not confusing the crap out of yourself. The latter takes some practice and granted, it may not be feasible in all areas of life, but at least in photography it's fairly manageable.

    I was shooting LF so no meter in the camera of course. Was using an incident light meter. I think what was tripping me up was I wasn't sure that lowering ISO 400 to 200 as increasing exposure. Now that I thought more about it I see it does because lowering the sensitivity of the film requires more light. By adding a -1 filter in effect what I did was lower the sensitivity of the film. OK, I'm good to process now. HC-110 Dil. H, TMax 400.



    Kent in SD
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  6. #6
    Vaughn's Avatar
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    Re: Probable Goof

    My experience with having different ISO films in my film holders and trying to keep track of which ISO to set on the meter tells me not to mess with the ISO on the meter unless required. I've messed that up enough times!

    So I do not change the ISO on the meter when I put on a filter. I just apply the filter factor after determining the base exposure without it.
    "Landscapes exist in the material world yet soar in the realms of the spirit..." Tsung Ping, 5th Century China

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