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  1. #161
    CPorter's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    yes, i do!
    Fog density would not be fog density if it also contained density from exposure to light, but why am I telling you that? Something is amiss.
    Last edited by CPorter; 12-29-2011 at 08:02 AM. Click to view previous post history.

  2. #162
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    Quote Originally Posted by PeterB View Post
    Originally Posted by CPorter
    come on, why should it let neglible light through, sounds like you are agreeing that where I want to read just fog must also have density from light.





    NO !!! The black tape used by CPorter as a mask should NOT let any light through. When I used the word negligible I intended it to mean "a sufficiently small amount (of light) that will not contribute to any measurable increase in density". Letting light through the tape that contributes to a density increase is contrary to the intention of using the black tape in the first place !!
    Ahh! That clears it up, forum communication can be tricky sometimes-----sorry for my contribution to that misunderstanding.

  3. #163
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    i prefer landscape photographing. for film testing as lambrecht descripes i need daylight or a daylight bulb.
    i want to use a daylight bulb because actually light conditions changes too fast.


    can you also recommend a daylight bulb for fim testing in this situation?


    whats with the setup?
    just photographing a white-sheet of paper in my room?


    best michael

  4. #164
    Bill Burk's Avatar
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    Although any light source other than real sunlight is a compromise, the repeatability of artificial light sources makes them a good compromise, if your tests don't need to result in laboratory grade accuracy. For example, my purposes I would be happy to be within 1/3 stop accuracy, 2/3 stop is tolerable. Once I get into the field to take pictures, I can't get my light meter readings to within 1/3 stop accuracy/repeatability anyway.

  5. #165
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    i work with a hasselblad 501cm.
    i put the stouffer 6x6 just into the film holder and make a contact print.
    it seams to work (did a test on one foto, the bars are fine)

    shooting 5 films with one holder costs time so i'm afraid that light conditions are changing during the test.

  6. #166
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    hello,

    after i did the first three tests with the stouffer 120 6x6 I got following results -> see pictures
    the steps 30/31 and 1/2 are missing because the stouffer wedge was displaced in the hasselblad filmholder :-(

    - why I have this "jump" on step 16 to 16 (other side of the step-wedge).
    - what do you think about those results in general?
    - should I have to repeat the whole process or should i go on with minute 13,4 and 19,5 ?

    best michael
    Attached Thumbnails Attached Thumbnails 2013-03-29_16-25-33.jpg   2013-03-29_16-27-04.jpg  

  7. #167
    Bill Burk's Avatar
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    Quote Originally Posted by Michael Hoth View Post
    hello,

    after i did the first three tests with the stouffer 120 6x6 I got following results -> see pictures
    the steps 30/31 and 1/2 are missing because the stouffer wedge was displaced in the hasselblad filmholder :-(

    - why I have this "jump" on step 16 to 16 (other side of the step-wedge).
    - what do you think about those results in general?
    - should I have to repeat the whole process or should i go on with minute 13,4 and 19,5 ?

    best michael
    Hi michael,

    Double-check your actual step wedge "calibration" densities.

    I don't think the jump is that dramatic, but it's interesting.

    When I drew a smooth dotted line between points, the "outlier" on the 9,75 curve was the point for Step 17.

    I see your calibrated value for Step 17 is 1.60. The "outlier" "fell into line" when I changed that value to 1.61. So double-check, maybe your calibrated wedge is 1.61

    Regards,

    Bill

  8. #168

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    Quote Originally Posted by Michael Hoth View Post
    - why I have this "jump" on step 16 to 16 (other side of the step-wedge).
    Michael, the jump probably means illumination onto the Stouffer was uneven. I suspect the right half of the chart got more light than the left part. If you're using an enlarger as a light-source, this could mean the film-holder was not centred under the enlarger, so that the left half was farther away from the centre, experiencing fall-off from the enlarger's lens. Or the light-output of the enlarger might be uneven.

    I suggest checking centring. You also might want to use an enlarger lens with a longer focal length and raise the head some. An easy way to test uniformity is to expose a piece of film in your film-holder, with *no* Stouffer present. Then measure density at various locations across the negative.

    Best,

    Mark Overton

  9. #169
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    thx,i used a step wedge-negative placing in the hasselblad filmholder, photographing a white card placing on zone X; did this with 5 films!

    maybe the displacing of the negativ leads to an uneven illumination (i lost steps 30/31 and 1/2)

    should i repeat shooting 5 films
    Attached Thumbnails Attached Thumbnails Foto.JPG  

  10. #170
    Bill Burk's Avatar
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    Quote Originally Posted by Michael Hoth View Post
    thx,i used a step wedge-negative placing in the hasselblad filmholder, photographing a white card placing on zone X; did this with 5 films!

    maybe the displacing of the negativ leads to an uneven illumination (i lost steps 30/31 and 1/2)

    should i repeat shooting 5 films
    No, I think it's expected to have a jump at 15-16-17 because those steps are near the edge. My edge densities are often "higher" than the inner densities. Just look at the overall trend and ignore the anomaly in the middle - consider it an artifact of the layout of the step wedge.



 

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