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  1. #1

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    Personal film speed w/o densitometer.......and Pyrocat HD

    After several years of serious shooting, I've never done a film speed test. I do not have access to a densitometer. Up 'til now, I've typically pulled one stop, reduced dev by 30%, and gotten decent results. However, I want to give testing a try.

    Today, under an even gray overcast sky, I exposed a roll of Classic 400 roll film at 4 different speeds: 400, 320, 250, and 160. I exposed 3 frames at each speed: as metered (i.e. zone 5), -4 stops (zone 1), and +3 stops (zone 8).

    Most of the articles I've read say that, after processing the film, I want to look for a zone 1 frame that has "slightly more tone" than the clear leader. Could I not use my light meter to help with this? If I meter through the clear leader (i.e. film base and fog), then look for a zone 1 frame that is 1 stop more dense, am I on the right track?

    Pyrocat HD: I plan to take the Formualry PMK times for Tri-X (14 min.) and HP-5 (13 min.) and call it 13.5 minutes for Classic 400. Then, knock off about 20% for Pyrocat HD.
    "If You Push Something Hard Enough, It Will fall over" - Fudd's First Law of Opposition

  2. #2
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    I do mine the simple way. When doing a contact sheet for testing, I give the contact just enough exposure to just barely see the edge of the film on the paper. YMMV, but at this point, the contact sheet will now give me a better idea on what my personal EI is. I just look for the shot that looks the best for density and range of tones. The setting on that frame will say choose me for your EI!

    If the density looks good but contrast is too low or high, you can switch grades or better yet, for me anyways, adjust the film development time up (bump up contrast) or down (lower contrast) to get the 'look' you want. Cheers.

  3. #3

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    Try out this link in the apug article section. It talks about testing with your light meter. Cheers.

  4. #4

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    Hmm.... on the test roll, exposed as noted above, I have no density at all on any of the zone 1 frames.
    "If You Push Something Hard Enough, It Will fall over" - Fudd's First Law of Opposition

  5. #5
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    Doug, this is why I use a step wedge for film tests. One shot gets you film speed and development information. Easier to see these relationships on one sheet of paper after it is printed.

  6. #6

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    Quote Originally Posted by noseoil
    Doug, this is why I use a step wedge for film tests. One shot gets you film speed and development information. Easier to see these relationships on one sheet of paper after it is printed.
    I'm all ears; tell me more.
    "If You Push Something Hard Enough, It Will fall over" - Fudd's First Law of Opposition

  7. #7
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    Quote Originally Posted by Doug Bennett
    ...Most of the articles I've read say that, after processing the film, I want to look for a zone 1 frame that has "slightly more tone" than the clear leader. Could I not use my light meter to help with this? If I meter through the clear leader (i.e. film base and fog), then look for a zone 1 frame that is 1 stop more dense, am I on the right track?...
    Doug,

    This sounds to me like you would be looking at a density more like zone II 1/2 since any density blocking a full stop above fbf would have a density of 0.30 more. Your film speed should be based on achieving about 1/3 stop or 0.10-0.15 above fbf.

    A very useful thing to acquire for doing film tests without a densitometer is a Kodak wratten #96 0.10 neutral density gelatin filter. That gives you a visual comparator that you can simply lay over the film base (e.g., an intentionally unexposed blank frame) and check against an adjacent exposed frame for the standard 0.10 density above fbf upon which film speeds are generally based. IIRC, Henry Horenstein's book on black and white photography also describes a simple 35mm film speed test based on using such a filter.

    The filter although not inexpensive is a very good investment and is a lot cheaper than a transmission densitometer. Should you decide to pick up a densitometer in the future, the ND filter can also be used to calibrate the low end of the instrument.

    Joe

  8. #8

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    Quote Originally Posted by smieglitz
    Doug,

    This sounds to me like you would be looking at a density more like zone II 1/2 since any density blocking a full stop above fbf would have a density of 0.30 more. Your film speed should be based on achieving about 1/3 stop or 0.10-0.15 above fbf.
    Joe,

    First of all, I thought Zone 1 was one stop above fbf, not 1/3 stop. Am I wrong here?

    What I was calling Zone 1 was exposed at -4 stops from "as metered", or Zone 5.

    I work in the theatrical lighting industry. We have .1 ND filters in stock. I didn't know it was the same ".1". Duh. :o
    "If You Push Something Hard Enough, It Will fall over" - Fudd's First Law of Opposition

  9. #9
    lee
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    point 10 above fb+f should be the same. in my feeble head

    lee\c

  10. #10
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    Quote Originally Posted by Doug Bennett
    Joe,

    First of all, I thought Zone 1 was one stop above fbf, not 1/3 stop. Am I wrong here?

    What I was calling Zone 1 was exposed at -4 stops from "as metered", or Zone 5.

    I work in the theatrical lighting industry. We have .1 ND filters in stock. I didn't know it was the same ".1". Duh. :o
    Doug,

    The density response of a film to a set exposure (i.e., a stop) is not linear over the range of the film. You are correct that -5 stops exposure is one stop less exposure than -4 stops, but that doesn't mean the densities will correspond neatly. Density is the log of opacity (which is the reciprocal of transmission) so that a density of 0.30 represents an increase in opacity of one stop or a cut in transmission of 50% of the previous value.

    Given a set increase in exposure by one stop (and standard development) the densities of corresponding zone exposures might be something like:


    zone 00 ( -6 stops from indicated meter reading) = fbf or 0.00 net density
    zone 0 ( -5 stops from indicated meter reading) = 0.02 net density above fbf
    zone I ( -4 stops from indicated meter reading) = 0.10 to 0.15 above fbf
    zone II ( -3 stops from indicated meter reading) = 0.25 above fbf
    zone III ( -2 stops from indicated meter reading) = 0.35 above fbf
    zone IV ( -1 stop from indicated meter reading) = 0.55 above fbf
    zone V (indicated meter reading) = 0.70 above fbf
    zone VI (+1 stop from indicated meter reading) = 0.85 above fbf
    zone VII (+2 stops from indicated meter reading) = 1.00 above fbf
    zone VIII (+3 stops from indicated meter reading) = 1.20 above fbf
    zone IX (+4 stops from indicated meter reading) = 1.40 above fbf
    zone X (+5 stops from indicated meter reading) = 1.50 above fbf

    Now these target density values will vary with the type of film used, developer, type of enlarger, paper type, camera format, etc., as well as which zone system text you read so they are not set in stone and others will give you different values. But, the point is that a constant one stop exposure change (input) ranges from about 45% to 65% increase in the resultant density change (output) and the rate of that change isn't constant. If it were a perfect 1:1 relationship between exposure and density (input to output), zone X would have a 3.00 net density value. Also, the rate of density change in the midtones is typically greater than that of the shadow and highlight zones.

    (Also, if you use a pyro based developer the stain adds to the effective zone densities for ultraviolet sensitive print processes, but that is another tale...)

    Check a standard zone system book for more detail on the above. (Ansel Adams' "The Negative" is the cornerstone text.)

    Trust me though, your zone I exposure (-4 stops from the indicated meter reading) should produce a density value above fbf of ~ 0.10 for medium & large format films, and ~ 0.15 for 35mm film.

    Joe

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