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Thread: Exposure variance by overall conditions

  1. #11

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    Re: Exposure variance by overall conditions

    Or your meter could simply be not as linear as you would want, resulting in more exposure in the more brightly-lit scene. If you're sure of your shutter speeds, and the exposure difference is apparent over the entire range of tones and not just the lower values, then this is the most likely explanation.

    Best,

    Doremus

  2. #12

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    Re: Exposure variance by overall conditions

    Quote Originally Posted by Ulophot View Post
    I checked Adams and Stroebel on flare last night. Adams speaks of bellows flare having potentially significant effects, but seems to indicate that the film edges may more affected, which is not my case. Perhaps it could be some overall lens flare, but I wouldn't expect this in the Komura, which, if I am not mistaken, is multicoated, and I have had it a long time; contrast appears good with no appearance of flare in subjects like a window light portrait including bright clothing, curtains, etc.
    It's flare all right. Adams doesn't address it much but he was aware of it. in one video he shows a negative of Garrapata beach and says "flare helped the shadows as expected". It reduces your negative density range, which will actually make your high-key negative easier to print.

    Imagine you are in a dark room and a friend shines a light in your eyes. No matter how you try, you will not be able to see your friend because the flare has illuminated your retina in general. It's like you lit up the whole room, there's no part of the room that's dark any more.

    I don't know if it's the right word for it but I think "aerial flare" would be a good description.

    And you could alter your EI in response to it, but I think you would be chasing a difficult to predict scenario.

  3. #13

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    Re: Exposure variance by overall conditions

    Quote Originally Posted by Ulophot View Post
    I suspect that it is my interpretations; using a spot meter is fairly new to me, and that may well be the weak link in my process chain.
    I concur. It is easy to say "I placed my shadows in Zone III" when they are actually Zone II or Zone IV. Your eye just needs to be calibrated through experience. Sounds like you have a good technical footing. Hang in there.

  4. #14

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    Re: Exposure variance by overall conditions

    Quote Originally Posted by Doremus Scudder View Post
    Or your meter could simply be not as linear as you would want, resulting in more exposure in the more brightly-lit scene. If you're sure of your shutter speeds, and the exposure difference is apparent over the entire range of tones and not just the lower values, then this is the most likely explanation.

    Best,

    Doremus
    That makes sense. I am only a bit surprised as the meter was cleaned, adjusted, and calibrated by Richard Ritter, who handled modifications of the meter for Zone VI; that, however, does not obviate your observation, a variable I had forgotten to consider. Meters have a kinship with many thermometers in this respect. Thank you.
    Philip Ulanowsky

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  5. #15

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    Re: Exposure variance by overall conditions

    You might create a "black box" - a cardboard box painted black or covered with black cloth inside with an opening cut out of the front.

    You might think this box always meters 0 or shows on film as same as unexposed film.

    But the meter will show some reading, and the film will show some exposure, and this would be due to flare.

    Your test result might have been caused by a slow shutter speed. From a distance, your spot meter may have indicated a reading that includes flare (if your reading up-close is different than the reading from camera position you can tell how much is flare).

  6. #16

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    Re: Exposure variance by overall conditions

    So many variables playing into this...and over time I have been so very thankful to threads such as this one which have served so well to help me improve my own craft.

    But there is one particular aspect of measuring light with a spot meter, which I feel deserves a bit more attention from us...which some might see as splitting hairs - and others may have already compensated for…either deliberately or intuitively.

    As much as I love my Zone-6 modified Pentax spot meter...I've also found, especially when out in the field, that its almost impossible (for me) to truly isolate a specific density in a given scene. Most of what I see - even within my light meter's one degree spot...is full of various micro-densities and/or zonal shifts (imagine anything remotely spherical) - and I truly believe that this contributes significantly to the visibly broader "zonal spectra" in my negatives than that which I'd originally been able to “evaluate” with my meter. Of course there are a host of other variables which all affect our zonal spectra…both as perceived by us and as realized in our results - which have been well covered on these threads.

    I bring up the above not only to simply add this variable to the mix of other more well established ones…but also to lament the long-ago passing of the SEI photometer…which, IMHO, provided the only truly effective means for reaching into a scene and providing an actual, isolated EV…limited only by a practitioners ability to perceive detail.

    For those unfamiliar with the SEI meter…it provides, in its field of view, a one-half degree “spot” which is actually a bulb-lit patch, the brightness of which, when aimed at the desired area of evaluation, is then adjusted with a rheostat until its intensity matches whatever detail within the patch which is of interest to the photographer. Lets imagine, for example, a fine, sunlit branch against a shadowed background…not only could the SEI isolate this branch, but…to the extent that the user could perceive this…it could allow further evaluation of any modulation of light over the branch itself - even if the branch occupied a small fraction of the area of the light patch! This is why I’d earlier placed the word spot in quotes…because the SEI's capacity to separate out EV’s extends to well within the patch itself.

    I own an SEI meter - paid 15 bucks at a yard sale…but it worked only briefly, just long enough for me to realize what a wonderful tool this could be, and long enough to truly wonder why the light measurement principle upon which this meter was based had not been embraced more broadly within the photographic industry. To be honest, the SEI, as wonderful as it was, was also large, heavy, slow, awkward. But when I think of how its technology could have been taken foreward...especially thinking of those of us for whom making accurate measurements is key - I have to wonder!

  7. #17

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    Re: Exposure variance by overall conditions

    Quote Originally Posted by John Layton View Post
    ...I own an SEI meter - paid 15 bucks at a yard sale…but it worked only briefly, just long enough for me to realize what a wonderful tool this could be, and long enough to truly wonder why the light measurement principle upon which this meter was based had not been embraced more broadly within the photographic industry...
    John – I also have an SEI meter, purchased new at my first AA Yosemite Workshop in ’66. I also got the anti-flare tube and extra bulb for it (just in case). It’s still functional. The anti-flare tube is about 3” long, black on the interior, that slips onto the meter’s telescopic optics; it has an orifice at its tip that blocks out much of the FOV around the spot. When I do my film speed tests with a white mount board target, I use a 31-step Stouffer against the film and a bellows shade to minimize camera/lens flare, then meter the board with the SEI and place the reading on Zone X. I’ve punched a hole in the step wedge to yield the Zone X density that includes fb+fog. The rebate density isolates the fog; I can then plot the characteristic curve as Net Density vs Zone.

    I certainly concur with your description as the large/heavy/slow/awkward; it rivals a 3 D-cell aluminum flashlight.

  8. #18
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    Re: Exposure variance by overall conditions

    A suggestion to increase understanding - record again the same 2 scenes with towels, foil, etc. using incident metering and constant EI.

  9. #19

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    Re: Exposure variance by overall conditions

    Chassis, an interesting suggestion, which I'll fold in to my continued explorations. My inclination at present is to try Marris's method to confirm my spot meter's linearity over the 8-stop or so range involved in my test. Ritter is such a fine technician that I suspect my own error may somehow be playing into all this more, but it could just be a chance in the meter (which was around a long time before it reached me) and this will be a useful check. Years ago as an active professional, I experimented a fair amount with my Gossen(s) between reflected and incident, and read numerous articles about tuning one's incident-reading craft in angular lighting conditions.

    By employing the flat t-shirt cloth, my test was designed to minimize potential discrepancies between what reflected and incident readings would yield; the towel, of course, responds quite differently to the side light from the window. As others above have noted, however, "micro-" reflections from fibers in a woven fabric can surprise. Were the difference not so great as my results have indicated, I wouldn't worry about it. As one who cut his proverbial teeth in 35mm journalistic work, printing "imperfect" negatives is not new to me. I look forward to continuing to hone my craft with help from the good folks in this forum.
    Philip Ulanowsky

    Sine scientia ars nihil est. (Without science/knowledge, art is nothing.)
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    https://www.flickr.com/photos/156933346@N07/

  10. #20

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    Re: Exposure variance by overall conditions

    Philip your post above reminds me of a Zone System course I taught years ago...which began with my handing out a (cheap) grey card to each student. When out in the field with these cards - I realized that results were all over the place...due to the amount of specularity exhibited by these cards - grrr! I then found a fancier one...forget who makes this, but its called "the Last Grey Card," (Bogen I think?) - which has an almost non-specular surface.

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