Accidentally pushed Fuji Acros 100!

Discussion in 'Fuji' started by Dickless Cheney, Nov 8, 2004.


  1. Since the film is already developed this is sort of moot but as a
    rule of thumb most films will push a stop by increasing the
    development time about 1.5 times. For two stops that comes out to
    somewhere around 3 to 4 times normal. Of course what you are really
    doing is increasing contrast. The assumption is that the wanted image
    is recorded in the toe region of the characteristic, which has much
    lower contrast than the normal exposure section. Increasing
    development increases the contrast of the toe enough to get some
    separation of the tones there but it also increases the overall
    contrast which may make parts of the picture which received more
    normal exposure hard to print. One stop pushing is about the same or a
    bit more than increasing contrast about one paper grade. Two stops
    push about two paper grades, maybe a little more for both. At some
    point, if the exposure falls low enough, the film simply doesn't
    record anything. No amount of pushing will recover an image. This
    limit is just about two stops for most films when using the ISO speed
    rating. Even at one stop there will be a degradation of shadow detail.
    The ISO method has virtually no safety factor (about 1.25). Up to
    1958 the method used had a 2.5X safty factor. A lot of films, like
    Tri-X, which got a reputation for being very pushable around then did
    so because the ASA speed ratings were a stop _over exposed_. You could
    get maybe three stops over the ASA speed, but this is the same as two
    stops over the ISO speed.
    Films like Kodak P3200T-Max can be pushed a lot because they have
    odd curves which result in an ISO speed much lower than the actual
    emulsion speed. The Kodak and Ilford films have ISO speeds of around
    800 to 1000 but the true speed is around 3000 to 4000 as the Kodak
    name suggests.

    Richard Knoppow
    Los Angeles, CA, USA
     
    Richard Knoppow, Nov 10, 2004
    #21
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  2. In my testing I have not found this to be the case.
     
    Uranium Committee, Nov 10, 2004
    #22
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