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  1. #31
    benjiboy's Avatar
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    In answer to your original question you need to buy one of these http://www.fotosense.co.uk/sekonic-e...ightmeter.html to calibrate the any particular film or digital sensor in addition to downloading the software from the Sekonic website to the L-758 meter. There is a video here http://www.youtube.com/watch?v=_7SZ58CugpY
    Last edited by benjiboy; 03-26-2010 at 03:21 PM. Click to view previous post history.
    Ben

  2. #32
    ignacj's Avatar
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    Ben,

    The video explains only digital camera calibration which I'm not really interested in. I'm looking for a film characteristic curve - say TMAX100 developed at 70F in Xtol 1:1 for 8 1/2 minutes. I guess I could scan my negatives and proceed with calibration as with a digital camera, but that would introduce scanner as an extra variable. I was hoping somebody already created film curves in more controlled lab environment that I could then use to program 758 directly. At very least I'd like to know dynamic range of any given film.

    Thanks for the links anyway.

    ig

  3. #33

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    ig, you don't have to depend on someone else to get an idea of how film X behaves in developer Y etc... Get a grey card and load your camera with the film you want to test. Place the card in a place where it's evenly lit, preferably by daylight. Get a reading with the meter and focus your lens at infinity. Now make a series of exposures from 5 stops underxposed to 5 stops overexposed. There should only be the grey card in the frame(s). If you wish to have additional precision (thirds of a stop), by all means do it, but that makes sense for the extremes of the of the exposure range, for instance between 5 and 4 stops underexposure. Process the film, let it dry and then:

    1) If you have a diffusion enlarger make a contact print of these strips, with the exposure needed for minimum time for maximum black though film base and a #2 filter.
    2) If you have a condenser enlarger you'd better make enlargements of these frames, again for the minimum for maximum black through film base, with a #2 filter. Making a contact print with a #3 filter will probably get you close, but enlargements will give more precision. After all, that's why you bought that meter for, didn't you?

    Now you can make an assessment and see what kind of results your equipment and technique will give, as long as you follow what you did in the test. If the results aren't what you'd have wished, you can repeat the test with different development for instance. In any case, everything is fine and dandy with development times etc proposed by manufacturers and anyone else out there, but it's your results that matter.

    PS Keep in mind that you have quite a bit of overexposure latitude with negative films. Just because you see a totally white frame at the contact sheet, it doesn't mean that there's no information there at all, unless you've grossly overdeveloped.

  4. #34
    KC2PED's Avatar
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    Has there been any change in the availability of downloadable film characteristic curves over the past 4 years. I have just spent next month's food money on an L-758 and am going to have to wait a few months (more if I buy film) before I can afford a target to start profiling so would be interested in a downloadable film profile to use as a starting point in the meantime.

  5. #35
    Bill Burk's Avatar
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    Hi KC2PED,

    No there isn't anything new on this frontier. I took a very simple shortcut which has made me happy because it's so plainly obvious.

    I decided to use the Zone System, and I just set the clipping points on Zones.

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