Step wedge alert

Discussion in 'B&W: Film, Paper, Chemistry' started by noseoil, Jan 27, 2005.

  1. noseoil

    noseoil Member

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    For those who are interested, I've posted a short summary of step wedge testing without a densitometer in the "How to articles" section. This is a very simple method of dealing with exposure and development, just the basics with no frills. tim
     
  2. photomc

    photomc Member

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    Perfect timing Tim...just got a Stouffer 21Step wedge in this week (4x5) so will read with great interest. Since I don't have a densitometer, this is perfect timing.

    Thanks
     
  3. noseoil

    noseoil Member

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    Mike, please take it with a large pinch of salt. tim
     
  4. mikeb_z5

    mikeb_z5 Member

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    Great I got mine yesteray! Thanks :smile:

    Mike
     
  5. Gim

    Gim Subscriber

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    This is great. I appreciate your effort. I have a step wedge on the way and all kinds of things have been going through my head on how to use it and get good information from it. This really helps
     
  6. photomc

    photomc Member

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    FWIIW - Ran film test yesterday following the steps outlined in the article, the sun finally came out - :smile:

    Tested some Efke PL100 4x5, in Rodinal 1+50 and must say was very pleased with what I have seen. Left the negatives to dry over night, so hope to print them this week (actually tonight). First, went ahead and exposed one film at rated speed (100), then one at 1/2 (50) - initial impression was this is good information so one can 'See' the impact of the change. Remaining test were done using 1/2 the rated speed. Have densitometer coming in later this week, so after I work through the graph process Tim covers in the article, I will check the information against the readings from the densitometer.

    So Tim, Thanks So Very Much for the article and the assistance...hope others find the article as useful as I have.
     
  7. Jim Chinn

    Jim Chinn Member

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    Thanks for taking the time to write up the article Tim. It's a nice addition to the resources here.
     
  8. JeffD

    JeffD Member

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    Ok, I am hoping someone can help explain my results. Here are the details:

    Tmax 100, exposed as e.i. 50
    developed in a jobo drum, constantly spinning on a beseler motor roller
    developed in hc110, dilution H (half the dilution of B) for 12 minutes, 68 degrees

    I have a densitometer which is acurately calibrated against a calibrated stouffer wedge.

    For each "patch" on my stouffer wedge, I figured out what zone exposure it was allowing my film to be exposed to. For instance, "patch" number one has a density of .04, therefore, I am giving my film, behind the wedge, an equivalent to a zone exposure of 9.87.

    math: 10 - (.04 / .3)

    Ok, so, I plot out all my density results (y axis) against the derived zone exposures, (x axis), and the enclosed jpeg shows my plotted curve. The film base plus fog has already been removed from the data before plotting.

    Question:

    Aside from the exessive contrast (I should probably use a time closer to 10 minutes, for normal), why is my film speed low?

    For my purposes, I am determining film speed by thinking that zone 1 exposure should be .1 . According to my chart, this speed is not reached until nearly zone 1.8, making TMAX 100, rated at e.i. 50 still needing to be bumped down to nearly e.i. 25!!! This doesn't seem right! I don't know of anyone deducting two full stops of speed from this film.

    Any ideas?

    Thanks!!

    PS
    Here is the spreadsheet, if anyone who is going through something similar wants to use it: http://www.hiddenworld.net/misc/curve.xls
     

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    Last edited by a moderator: Feb 19, 2005
  9. dr bob

    dr bob Member

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    I can't seem to download the speadsheet.
     
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  10. JeffD

    JeffD Member

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    Not sure why.....
     
  11. noseoil

    noseoil Member

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    Jeff, not exactly sure what's going on with your test. Two things I would try:

    First, expose a sheet of film in your camera at 25 and see what results you get with the 10 minute development time. Take a real picture and evaluate it. How does it look?

    Second, I'm using an exposure setting on Efke 25 of asa6. Works great. Don't use that fancy new film at this point. tim