Test procedure for even development?

Discussion in 'B&W: Film, Paper, Chemistry' started by Jeff Bannow, Aug 2, 2012.

  1. Jeff Bannow

    Jeff Bannow Member

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    I would like to run a test of my 4x5 sheet film development process, specifically looking for evenness from agitation. Here's my plan:

    1. Find an evenly lit wall in the sunshine and meter for middle gray. Take a picture.
    2. Develop.
    3. Examine and look for any anomalies on the light table.

    This seems so simple, that I must be missing something. Anyone have a preferred method?
     
  2. Overkill-F2

    Overkill-F2 Member

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    Are you tray developing your 4x5's?
    I might expose three sheets, zone 3, 5 and 7, contact print, then examine them.
    ...Terry
     
  3. Jeff Bannow

    Jeff Bannow Member

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    This will be inversion processing.
     
  4. wildbill

    wildbill Member

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    Jobo, expert drum.
     
  5. albada

    albada Member

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    Illumination of lenses tend to fall off near the edges and corners. Perhaps expose the film using the enlarger at f/16 instead? Or put the film on the counter and blink a light in the darkroom?
    Also, the human visual system has a hard time seeing gradual changes in luminance. I suggest using a densitomer, or placing a light meter in various places on the film to measure densities.

    Mark Overton
     
  6. Jeff Bannow

    Jeff Bannow Member

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    Sold my Jobo, Vinny. :smile:
     
  7. michael_r

    michael_r Subscriber

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    Use your enlarger - assuming it illuminates evenly. Raise the head way up and stop down so there's no falloff. Expose a sheet of film to some mid-tone density. Process it. And then contact print it.

    What kind of tank/system are you using for inversion?
     
  8. Jeff Bannow

    Jeff Bannow Member

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    Interesting - I've never exposed film via my enlarger before actually.

    So:

    Turn off safelight.
    Get the enlarger head to a point with even illumination and stop down lens.
    Use incident meter to make exposure in the multiple second range.

    I assume I could just do all of this in a normal double-darkslide 4x5 holder.
     
  9. michael_r

    michael_r Subscriber

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    Ideally I'd just put the sheet flat on a piece of black cardboard on the enlarger baseboard (to eliminate any chance of flare from the film holder along the edges of the film).

    What kind of tank/system for inversion?
     
  10. Jeff Bannow

    Jeff Bannow Member

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    Mod54 in a Patterson tank.
     
  11. Lee L

    Lee L Member

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    You might find that exposure from a sufficiently distant, possibly diffuse light source will give a more even exposure on the original neg.

    Also contact print the neg under even light on grade 5 paper or with grade 5-6 VC filter to make uneven development more apparent.

    Lee
     
  12. ic-racer

    ic-racer Member

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    Yes, I'd expose and print like Lee suggests. To quantify evenness you can check the center and 4 corners with your densitometer (or send it to one of us).
     
  13. Jeff Bannow

    Jeff Bannow Member

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    Thanks guys. Any suggestions on a light source?

    And I assume I set my light meter to f1?
     
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  15. ic-racer

    ic-racer Member

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    I'd expose the film in a film holder with a light from across the room.
     
  16. Bill Burk

    Bill Burk Subscriber

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    Haaa, Let's see... I just went through this...

    TMY-2, set enlarger so incident meter reads EV0 with the "flat" dome (at ISO 100)

    Expose for 5 seconds...

    That gives me the same amount of "light" as my sensitometer.

    Now you want something middle gray I suppose, a density around say 0.60 sound good?

    That graphs under Stouffer scale step 14 which is 1.98 density.

    So if you expose film that much less than the full 5 seconds at EV0, you will possibly get 0.60 density when developed.

    1.98 divided by 0.3 is 6.6 stops...

    So somewhere about an 1/8 or 1/15 second should do the trick...
     
  17. Mark Fisher

    Mark Fisher Subscriber

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    Is there any light fall off in your enlarger....I'd check that with a light meter before using that method. I know that I get a little fall off with my D2 in 4x5. If you do it in-camera, I'd still check the corners just to see how much light variation there might be.......also, you might defocus heavily just to remove any texture
     
  18. michael_r

    michael_r Subscriber

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    You can test for enlarger light evenness with a spot meter, aiming it at the center, corners etc from the lens axis. Don't overcomplicate this.

    Regarding the Mod54, I'm testing this product now as it happens. One thing I don't like already, the tabs that hold the film extend too far out into the image area, causing tiny scratches on the base side of the film as the film slides up and down in the holder during inversion. I'm also finding I need significantly more than 1L of developer for it to work properly (not a problem, but worth noting). Lastly, I would suggest doing only two sheets at a time in this thing rather than 6. Testing is preliminary so far, but I still find tray development in a thin wire slosher to be the easiest way to get uniform development, including Pyro. The only thing better than the slosher is doing a single sheet in a tray. Of course the Jobo is reputed to be excellent, but I've never used one.
     
  19. dpurdy

    dpurdy Member

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    I would suggest using a zone 7 density rather than zone 5 because in my experience uneveness problems will show up more.
    Back in my days of shooting products on a blank light grey it was a real headache getting it even.
    Also because it is useful to have your zone 7 processing time down.

    If using your enlarger make sure it is way out of focus from the light source.

    Dennis
     
  20. Bob Carnie

    Bob Carnie Subscriber

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    Jeff we would do a basic copy shot of a large greycard.. make sure that the original is evenly lit.
    process as normal and read the film on a densitometer.
    If all is well each film that is in different positions of the rack , or each film within the run if Jobo should read identical.
    If not your process is off.. I suspect this has to do with the nitrogen burst thread and it is a really good idea to do this, test to check for even development
    If you do not have a densitometer on hand someone in your area could read the film and sharpie the numbers.
    We measured 9 spots on each film to see how even the run is.

     
  21. ic-racer

    ic-racer Member

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    All enlargers with lenses have light falloff, unless you have a density filter/diffuser made especially for a particular magnification ratio and lens and aperture.
    Exposing a film under the enlarger is a different test. That is a test of enlarger light evenness.
    Graph shows composite results from 135 and 150mm Schneider Componon-S. The picture is a piece of film exposed under an enlarger and processed to a high gamma to accentuate unevenness.
    [​IMG]
    [​IMG]
     
    Last edited by a moderator: Aug 3, 2012
  22. Bill Burk

    Bill Burk Subscriber

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    I was going to say that is awful - makes using an enlarger for sensitometer look like a bad idea.

    Until I realized. I keep the enlarger locked at the height to make an 11x14 print from 4x5 neg. So I am only using the sweet spot near the middle.

    I placed the film squarely under the lens, but positioned the test strip on the left-hand side - so maybe I fortunately avoided the hot-spot at dead center.

    And I am using a grid light source, not condenser.

    What is your light source (does the lens really have a hot spot in the middle or do condensers play into it)?
     
  23. michael_r

    michael_r Subscriber

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    Any light source is subject to falloff off-axis.

    I raise the enlarger head (diffusion) way up for a giant print size. The little 4x5 negative is in the middle of a comparatively huge imge circle and within that 4x5 area I don't have variations of even 1/10 stop. That's good enough for me. But if someone prefers to use a softbox 30 feet from film taped to a wall that's probably good too.

    Anyhow best of luck to OP. I would be curious to hear about your results with the Mod54.
     
  24. Bob Carnie

    Bob Carnie Subscriber

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    Michael is right, he is not using the edges. I have used enlargers for this test as well as lighting on a copy board.
    I prefer the copy board method as I am tethered and can read the numbers for eveness.
     
  25. Jeff Bannow

    Jeff Bannow Member

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    Thanks everyone for the advice.
     
  26. Bill Burk

    Bill Burk Subscriber

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    That graphs under Stouffer scale step 11 which is 1.56 density.

    So if you expose film that much less than the full 5 seconds at EV0, you will possibly get 1.0 density when developed.

    1.56 divided by 0.3 is 5.2 stops...

    So somewhere about a 1/4 or 1/8 second should do the trick...