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Thread: Exposing BW sheet film for film/developer testing

  1. #1
    Eric Woodbury
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    Exposing BW sheet film for film/developer testing

    I've been doing some film developer combo testing. Anybody have some clever way to do this? Usually I set up a set of targets (black, grey, white cards) in the sun and take a series of test images. Right now, all we have here is clouds and mud. Sometimes I image a step wedge. This has its moments, too, but doesn't really tell you what an image will look like. Lately, I have been imaging inside under lights, but I don't really have a lot of indoor space. I can calibrate out the tungsten shift.

    What I'd like is some means to use an enlarger with a coldlight. Seems possible. I guess I could put a step wedge in the enlarger and a shutter on the enlarger, but I am worried about the light leakage and to some degree the color of the light, but I could plug up the holes and calibrate the color shift. It doesn't really tell me the quality.

    It just may be that there is no one good answer, but I thought I'd ask what others are doing --- you are a clever bunch.
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  2. #2
    ic-racer's Avatar
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    Re: Exposing BW sheet film for film/developer testing

    Actually, there are a lot of ways to do this.

    You can contact the step wedge using the enlarger. This is a makeshift sensitometer. Use a glass to get it flat for best results. If you project it you don't know your values for the x-axis (unless you have an enlarging exposure meter). If you contact, then you x-axis values can be obtained by reading your step wedge with your densitometer.
    You can also use a camera as a sensitometer by affixing the step wedge to a sheet of film (large format camera) and aiming at a uniform target. (to tedious for me, but some do it this way).

    IF you are going to do routine testing, you can just buy a sensitometer.

  3. #3
    Eric Woodbury
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    Re: Exposing BW sheet film for film/developer testing

    ic-racer

    with 400 ASA film, do you use a shutter on the enlarger?
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  4. #4
    ic-racer's Avatar
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    Re: Exposing BW sheet film for film/developer testing

    Quote Originally Posted by Eric Woodbury View Post
    ic-racer

    with 400 ASA film, do you use a shutter on the enlarger?
    Before I got my sensitometer I used the digital enlarging timer set to something less than 1 sec. Set the aperture small, enlarger column high. You could use ND filters also.

    Even with a sensitometer, you have to fiddle with the light intensity to match the film to the step wedge. Even more fiddling to fit a range of film speeds on the step wedge so you can do relative-speed comparison testing.

  5. #5
    Maris Rusis's Avatar
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    Re: Exposing BW sheet film for film/developer testing

    I test film, usually in the 8x10 format, by making a series of exposures from Zone 1 to Zone X by moving the dark-slide stepwise across the film for each exposure. My target is usually a white sheet evenly lit in sunlight.

    In the darkroom I cut the film into four equal strips with each one bearing the ten step exposure sequence. Then all four strips go into the developer at once and get routine tray agitation. At regular intervals, say 2 minutes, 4, 8, and 16 minutes, I take a film strip out of the developer tray and put it in the stop bath. After 16 minutes I take all the film strips through the usual fix, wash, dry routine.

    The end result is 10 exposures for each of four different developments. The data, plotted out in the usual D versus log Exposure format, give me four curves and everything I need to know about EI, and N-, N, and N+ development either directly or by simple interpolation.

    Total cost: a sheet of film, some chemicals, and a couple of hours.
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  6. #6

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    Re: Exposing BW sheet film for film/developer testing

    I just finished doing this with HP5, and Dektol 1:2 following Fred Picker's procedure.

    Mike

  7. #7

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    Re: Exposing BW sheet film for film/developer testing

    Quote Originally Posted by Eric Woodbury View Post

    What I'd like is some means to use an enlarger with a coldlight. Seems possible. I guess I could put a step wedge in the enlarger and a shutter on the enlarger, but I am worried about the light leakage and to some degree the color of the light, but I could plug up the holes and calibrate the color shift. It doesn't really tell me the quality.
    Phil Davis' method of testing film was based on contact printing a step wedge to film using an enlarger. Get a copy of his book, Beyond the Zone System, and there is a good description of how this is done. I used an enlarger plus a Metrolux timer (which is based on light integration) and it worked perfectly for testing film.

    One can also expose film with a sensitometer. They come up from time to time on ebay.

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    Re: Exposing BW sheet film for film/developer testing

    Quote Originally Posted by Maris Rusis View Post
    I test film, usually in the 8x10 format, by making a series of exposures from Zone 1 to Zone X by moving the dark-slide stepwise across the film for each exposure. My target is usually a white sheet evenly lit in sunlight.
    Maris,
    I like your method. However, its making my head hurt, thinking about how you might be using your darkslide to do that. Are you simply exposing the entire sheet, for say zone 1, then move your darkslide it in a bit, and then stacking the additional time that would be required for say zone 2, and then 3 etc.?
    Go buy some film, and release the magic.

  9. #9

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    Re: Exposing BW sheet film for film/developer testing

    Quote Originally Posted by Tim k View Post
    Maris,
    I like your method. However, its making my head hurt, thinking about how you might be using your darkslide to do that. Are you simply exposing the entire sheet, for say zone 1, then move your darkslide it in a bit, and then stacking the additional time that would be required for say zone 2, and then 3 etc.?
    Start with slide closed. Open a little.

    Give zone 9 exposure. (metered value opened up 4 stops)
    move slide out a little more
    Give zone 8 exposure (metered value opened up 3 stops)
    move slide out a little more
    Give zone 7 exposure (metered value opened up 2 stops)
    move slide out a little more
    Give zone 6 exposure (metered value opened up 1 stops)
    move slide out a little more
    Give zone 5 exposure (metered value)
    move slide out a little more
    Give zone 4 exposure (metered value closed down 1 stop)
    move slide out a little more
    Give zone 3 exposure (metered value closed down 2 stops)
    move slide out a little more
    Give zone 2 exposure (metered value closed down 3 stops)
    move slide out a little more
    Give zone 1 exposure (metered value closed down 4 stops)
    move slide out a little more
    Give zone 0 exposure (metered value closed down 5 stops)

    as the darkslide is pulled exposing each strip of film, the first bit of exposure that strip is given is one stop less than it will finally receive via the accumulation of subsequent exposures so that it has in total 1 stop more exposure than it got on its first exposure.
    So the very first exposure at zone 9 will end up with zone 9 + all of the exposures for zone 8 thru zone 0 which is equivalent to a zone 10 exposure.

  10. #10

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    Re: Exposing BW sheet film for film/developer testing

    Sometimes I image a step wedge. This has its moments, too, but doesn't really tell you what an image will look like.

    Here's a fairly straightforward method that will tell you what your images will look like.

    http://www.kenleegallery.com/html/tech/testing.html

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