Finding correct exposure times...

Discussion in 'B&W: Film, Paper, Chemistry' started by ChristopherCoy, Sep 5, 2011.

  1. ChristopherCoy

    ChristopherCoy Member

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    When I was in high school, my photography teacher taught us how to use 'test strips'. We'd take the strips of paper, put them under the enlarger, cover them with a piece of black cardboard, and expose for 5 seconds. Then we'd move the cover down exposing more of the paper, and then expose for another 5 seconds. Then again, then again, then again, until we had exposed the entire 'test strip'. She told us to choose the exposure that gave us the 'whitest whites and the blackest blacks', and each interval represented 5 seconds.

    I'm sure that this is quite the amateur way to do things, but wondered what, if any, the best method is to find the proper exposure time.
     
  2. MattKing

    MattKing Subscriber

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    Things haven't changed a lot since high school :smile:.

    This is covered in many good books. Henry Horenstein's "Black & White Photography - A Basic Manual" comes to mind. As do many more advanced tomes, like Ralph Lambrecht and Chris Woodhouse's "Way Beyond Monochrome"

    Here is a useful internet reference from APUG member ROL: http://www.rangeoflightphotography.com/pages/making-a-fine-art-print

    Ralph Lambrecht (and others) recommend that if you can you should move the paper instead of the cover, because that results in test segments that include the same area each time.

    As for choice of exposure, I'd differ slightly with your teacher. You should choose the exposure that gives you the mid-tones you like and, hopefully the detail you want in the whites. You then adjust the contrast to achieve the blacks you want. If necessary, you can burn in the highlights to add detail.

    And as for the progression of times, I prefer the following: 6, 8, 11, 16, 22, 32 (all in seconds)

    If you are progressively uncovering more and more of the image, use this: 6, +2 more, +3 more, +5 more, +6 more, +10 more (all in seconds)

    Have fun
     
  3. Blighty

    Blighty Subscriber

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    Using a sequence such as described by Matt will give you 'equal' steps of increasing exposure and is, I think, the basis for the 'f stop' method of print exposure. 'Way beyond monochrome' explains it all rather nicely. B.
     
  4. Jeff Kubach

    Jeff Kubach Member

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    I do the same thing for years!

    Jeff
     
  5. Gerald C Koch

    Gerald C Koch Member

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    For many years Kodak used to market a handy device to make a series of test exposures all at once. It consisted of a sheet of plastic with a series of pie wedges each having an increasing density. You would expose a sheet of paper for 1 minute with the template on top of it. You would then look at the resulting print and pick the wedge with the best exposure. The times were given for each wedge.
     
  6. MattKing

    MattKing Subscriber

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    They were called the Kodak Projection Print Scale.

    They are not made any more, but can often be found used.

    There are new ones from competitors though:

    http://www.adorama.com/DKPPS.html
     
  7. piu58

    piu58 Member

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    Test strips are for getting the right exposure time and the right contrast (with variable paper). I always add ~1/3 stop at every step. I use a metronome because I find it much more comfortable for burning and dodging.
    I count with the metronome and use the times 10-13-16-20-25-32 ... seconds, which are separated 1/3 stop, rounded to the next second.
    I look for the right contrast of the following way: I always include a small strip of the blank film in my strip. I select the first exposure which gives maximum black. If the negative is not overexposed, this is in the near of the final basic time. Then I look for the highlights. If they are O.K. in the same strip - fine. I am finished. If good separated highlights are found in the strip with 1/3 less light, I have to use 1/2 a step higher graduation (more magenta or less yellow), without changing the exposure time. If I find the highlights in the strip 1/3 stop more exposed, you need half a step less graduation (more yellow or less magenta). You can expand this until 2/3 steps. If you are farther away I recommend a second strip. A don’t step the second strip but exposure it with the time and paper contrast form the first strip (the second, if your first was far away from the optimum).

    With this method I get after the first strip exposure time and paper contrast which lie quite in the near of the optimum. The second strip (mostly half a sheet for me) is for estimate the need for burning and dodging which I use in nearly every photo. Beside of this it is valuable for small corrections of the basic time.

    I wrote a text hich illustrated this, but is is in German. May be you cann see something from the images alone, or you use some internat translation program:
    Test strip method in German
     
  8. ChristopherCoy

    ChristopherCoy Member

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