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  1. #11
    RalphLambrecht's Avatar
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    Customizing Film Speed and Development 215
    2. Fast and Practical
    Here is another way to arrive at your effective film speed and customized development time. It is a very practical approach, which considers the entire image producing process from film exposure to the final print. The results are more accurate than from the previous method, and it requires three simple tests, but no special equipment.
    a. Paper-Black Density Test
    This test will define the minimum print exposure required to produce a near-maximum paper density. Make sure to use a blank negative from a fully processed film of the same brand as to be tested. Add a scratch or a mark to it, and use it later as a focus aid.
    1. Insert the blank negative into the negative carrier.
    2. Set the enlarger height to project a full-frame 8x10 inch print and insert contrast filter 2 or equivalent.
    3. Focus accurately, then measure and record the distance from the easel to the film.
    4. Stop the lens down by 3 stops and record the f/stop.
    5. Prepare a test strip with 8, 10, 13, 16, 20, 25 and 32-second exposures.
    6. Process and dry normally.
    7. In normal room light, make sure that you have at least two but not more than five exposures, which
    relative log exposure [lx·s]
    base+fogtransmission density ISOfilm speed1.30 0.80 ±0.050.10Hm   = 0.615
    the proper exposure and development of the film. This requires adjustment of the manufacturer’s film speed (or ‘box speed’) and development suggestions.
    In general, advertised ISO film speeds are too optimistic and suggested development times are too long. It is more appropriate to establish an ‘effective film speed’ and a customized development time, which are personalized to the photographer’s materials and technique. In most literature, the effective film speed is referred to as the exposure index (EI). Exposure index was a term used in older versions of the standard to describe a safety factor, but it was dropped with the standard update of 1960. Nevertheless, the term ‘EI’ is widely used when referring to the effective film speed, and we will accept the convention.
    Still, we ask ourselves: How does one establish the effective film speed and development time to compensate for different subject brightness ranges? An organized test sequence can give you very accurate results, but even a few basic guidelines can make a big difference in picture quality. I would like to show you three different ways, with increasing amount of effort, to keep you from wasting your time on too many ‘trial and error’ methods.
    1. Quick and Easy
    Here is a simple technique, which will improve picture quality significantly and does not require any testing at all. Use it if you dislike testing with a passion, or if you just don’t have the time for a test at the moment. This method can also be used to give a new film a test drive and compare it to the one you are using now.
    For a normal contrast, bright but cloudy day, cut the manufacturer’s recommended film speed by 2/3 stop (i.e. ISO 400/27° becomes ISO 250/25°) and the recommended development time by 15%. The increased exposure will boost the shadow detail, and the reduced development time will prevent the highlights from becoming too dense. For a high-contrast, bright and sunny day, increase the exposure by an additional 2/3 stop (i.e., ISO 400/27° now becomes ISO 160/23°) and reduce the development time by a total of 30%. Stick to the ‘box speed’ and suggested development time for images taken on a low-contrast, rainy or foggy day.
    A negative processed this way will easily print with a diffusion enlarger on grade-2 or 2.5 papers. Just give it a try (fig.1). It is really that simple to make a significant improvement to negative and image quality.
    de
    velopment timefilm speed[ASA]scene contrast-- 2/3- 1 1/3low-normal- 15%high- 30%adjustmentstypical subject brightness rangerainy or foggy daybright but cloudy daybright sunny day
    fig.2 Film exposure and development in accordance with the current ISO standard.
    fig.1 It is possible to make significant improvements to negative and image quality without any testing. Use this table to deviate from the manufacture’s recommendations for film exposure and development according to overall scene contrast.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  2. #12

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    Ralph - I'm afraid your post got a bit mixed up. At point 7 above it looks like several sentences are mixed in, and I just can't follow your post beyond that point.

  3. #13
    Leigh B's Avatar
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    Hi Craig,

    Your test procedure sounds excellent to me. You certainly don't need any outside intervention.

    Now try making some enlargements to see if your assessment holds up under magnification.

    Remember, you can always burn in highlights if they lack detail on the print, as long as there is detail in the denser areas of the negative.
    You can't add detail in the shadow areas beyond what's on the negative. That's why most folks overexpose by some amount v. the film box speed.

    It appears you came to that same exact conclusion. Congratulations.

    - Leigh
    “Wise men talk because they have something to say; fools, because they have to say something.” - Plato

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