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  1. #11

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    Quote Originally Posted by Helen B View Post

    "...its relevance to metering is slight, as no speed criterion ever has been based on a mid-tone. Speeds for negative materials are based on shadow detail,..."

    Well, that's a bit of a grey area. There is a technique known as Aim Density that uses the density of a grey card exposure as the determining factor for speed. It's used in cinematography with colour negative materials, and there are a few variations. It uses midtones, because they tend to be the most important tones in most movies. Well anyway, that's what I think.
    Dear Helen,

    You are of course absolutely correct, as usual. I could be picky and say that this is not an ISO standard, but in cinematography, a mid-tone is indeed a de facto standard -- or, from what little I understand of the subject, a flesh tone, especially a highlight flesh tone on the female lead. Early books on spot metering devoted quite a lot of time to this. My understanding is that this is all in the interests of continuity from one shot to the next.

    I'd still say that even after allowing for your correction, my observation about neg speeds holds good for non-cinematographers.

    Oh: and thanks for the wonderful picture.

    Cheers,

    R.

  2. #12

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    What I do to check the meter of an unknown camera is the following.
    1. I put my Beseler computerized color head on its side and dial in all three filter to get an EV14@ISO100 at its diffuser. I check the light level using my Minolta flashmeter VI in spot mode.
    2. I point the camera at this about a couple of inches from the diffuser and with the lens focus at infinity. I check and see if the shutter speed and aperture combination on the camera is at EV14.
    3. I dial in 150cc of all three color and this should bring the brightness down to EV9@ISO100. I check it with the spotmeter.
    4. I point the camera at this target and see what the reading is.

    If at this 2 points the meter readout on camera is kinda OK then I think the meter is OK.
    The method leaves a lot to be desired but it work well enough for me.

  3. #13

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    "The film manufacturer gives you red, green and blue Status M aim densities for a grey card. You expose a grey card at different effective meter settings, using your meters, in third-stop intervals. Then you measure the Status M densities and find the setting that came closest to the recommended values for each layer. The speed is calculated by voting: eg 250, 320, 320 means 320. Then you use that as your basis for the rest of your film testing, which is a mixture of numbers and appearance, and which is the larger part of the exercise."

    Helen, I like this method as it determine the exposure accuracy overall not just the light meter or shutter speed or aperture accuracy. However, I ran into trouble using this technique recently because I can't find a reliable film processor to process my C41 film.

  4. #14
    Ed Sukach's Avatar
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    Having been involved in the calibration of Photometers - sundry different levels of sophistication - I can only recommend - for sanity's sake - to return it to the manufacturer, or a well - equipped repair shop.

    Every other "at-home" method I can think about will NOT be accurate enough to determine the meters accuracy; e.g., if it falls within the manufacturer's tolerances.

    BTW ... It is interesting to note just what the manufacturer's tolerances are, information that is may be difficult to obtain. The specifications for the Gossen "UtraPro" that I have lists +/- 1/3 "Stop". That CAN mean that two "in tolerance" meters, one towards the high side; the other toward the "low" will differ by 2/3 stop.

    I have read the treatise on "Grey Cards" in the mentioned web site - and I will confess that I felt something like a ping-pong ball - bouncing from "completely useless" to "pretty good in some circumstances."
    My opinion? A useful tool. Not perfect - but then again - nothing is (not even a "spot meter"). It is a good thing to understand the theory and variabilities involved in their use... as it is with everyhing else in photography.
    Carpe erratum!!

    Ed Sukach, FFP.

  5. #15
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    One final point - if you use the palm of your hand, and you are light skinned, and you spend a lot of time outdoors in the summers, you may need to compensate for the "tanning" effect during certain parts of the year.

    Matt

  6. #16

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    Matt,

    What's your secret? I have long desired tan palms, but they continue to elude me. One day I hope to have tan palms to match the rest of my hand.

    Jmal

  7. #17

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    Quote Originally Posted by jmal View Post
    Matt,

    What's your secret? I have long desired tan palms, but they continue to elude me. One day I hope to have tan palms to match the rest of my hand.

    Jmal
    Get enough hair on them and the luminance drops to the same level.

    I have to admit that I've never suffered from tanned palms either, even when living in Malta, one of the sunniest places on earth.

    I'll have to lend one of my West Indian chums a meter...

    Cheers,

    R.

  8. #18
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    Quote Originally Posted by jmal View Post
    Matt,

    What's your secret? I have long desired tan palms, but they continue to elude me. One day I hope to have tan palms to match the rest of my hand.

    Jmal
    Jmal:

    They are never as tanned as the back, but they are usually darker at the end of the summer then the paste-white colour they achieve by winter's end.

    Matt

  9. #19

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    Quote Originally Posted by Ed Sukach View Post
    "Grey Cards" ... Not perfect - but then again - nothing is (not even a "spot meter"). It is a good thing to understand the theory and variabilities involved in their use... as it is with everyhing else in photography.
    Well, that's it. As long as people understand that (a) grey cards aren't a panacea (b) they're not a lot more use than white paper and (c) they don't represent the reflectance of an 'average scene', they might as well buy one. I own two or three, though I seldom use them.

    As so often, people need to stop worrying that there's some Big Secret they don't know, because usually, there isn't. It's more often a matter of assembling small bits of information; beginning to have some idea of the theory behind what you're doing; and practise, practise, practise (or practise x3, in American). Totemism and its associated jargon are a short cut to lousy pictures.

    Cheers,

    R.

  10. #20

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    Roger,

    I use the hair for metering shadow detail. Mid tones and shadows on one portable device.

    Jmal

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