Camera as Extinction Meter?

Discussion in 'Exposure Discussion' started by kintatsu, Jan 9, 2013.

  1. kintatsu

    kintatsu Member

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    I recently read in the Kodak Master Photoguide from 1951, that the camera can be used as an extinction meter.

    By focusing on a dark object and stopping down until only slight detail remains, and consulting a chart, an accurate exposure can be made. The chart shows times for Kodak Super-XX, which shows an index of 100, that would be about ISO 200, in today's scale. From what I can find about that film, the reciprocity issues normally associated with longer exposures were virtually nonexistent.

    Does anyone have any experience with this? Would only calculating the exposure from the table for your film speed and adding for reciprocity provide a correct exposure? I tried it on my digital, and got decent results.

    I just wanted to see what folks have experienced before using up some film. Thanks!
     
  2. Mustafa Umut Sarac

    Mustafa Umut Sarac Member

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    Very interesting question if I understood correctly. I think you are talking about SLRs , you look from the visor and find the darkest point , set the aperture ring to a darkest visible point for the shadow and than ? Where can we find such a chart ?
    Can you attach a scan ? What happens to highlights ?
     
  3. kintatsu

    kintatsu Member

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    The Kodak book mentions using ground glass focusing. According to the book, you focus with darkest important part in the center, and stop down until detail is just barely visible.

    The chart in the book is for super-XX, and shows in order, darkest detail seen at, then exposure time and f/stop, as follows;
    at f/8 expose 32 seconds at f/16
    at f/16 expose 8 seconds at f/16
    at f/32 expose 2 seconds at f/16
    at f/64 expose 1/2 second at f/16
    Other exposures and values can be calculated from there, IE at f/11 expose for 16 seconds at f/16.

    The book was Kodak's Master Photoguide, printed in 1951. I tried doing that with my digital, and got decent results. The correct times may need some adjustment for the newer ISO standards, as opposed to Kodak's index of 100 for film speed. Of course, reciprocity may be an issue. With the highlights, I would assume that if the exposure is longer than, say, 8 seconds, then development change would be needed.
     
  4. Mustafa Umut Sarac

    Mustafa Umut Sarac Member

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    Thank you for your answers.

    Umut
     
  5. artonpaper

    artonpaper Subscriber

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    Very interesting, I will give it a go next time my self.
     
  6. E. von Hoegh

    E. von Hoegh Member

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    This is a "rough n ready" method at best. With the current fashion of using a black T-shirt in lieu of a proper dark cloth I'd place no confidence in the results. Even using a real dark cloth, the results will depend on how well your eyeballs have adapted to the dark.

    A careful worker could get decent results, but there's that word, "careful". :wink:
     
  7. kintatsu

    kintatsu Member

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    My concern is the reciprocity. From what little I can find, Super-XX had almost 0 reciprocity effect. Knowing the reciprocity characteristics of the old film would help target a proper exposure for the film I'm using now.

    Super-xx was rated at 100, that's before the big switch, though. So the first part is calculating the speed difference, whether or not to use the stated speed or the post-change speed. After that is the reciprocity. I don't see why it wouldn't work, and do so quite reliably, once those 2 bits were known.

    Practicing with my digital camera may provide some help dialing in a chart for today's speeds, as settings are controllable and the feedback is quick, although I'd like to hear from someone who's tried it rather than resort to my other camera.
     
  8. kintatsu

    kintatsu Member

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    Yeah, careful.

    I use a thick brown blanket right now, and it still takes some time to get focus spot on, so add a couple more minutes deciphering detail and values, and it could be time consuming. With practice and the right knowledge, though, it may be worth the effort. Especially when my meter is my digital camera!
     
  9. E. von Hoegh

    E. von Hoegh Member

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    I've read of this method, but never used it. I have used an old exctintion-type "meter" and can tell you this: get a proper exposure meter. A used LunaPro can be had for $50 or so. How many sheets of film does that represent?
     
  10. kintatsu

    kintatsu Member

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    Actually, I use both the Gossen Sixtomat and the Sixtino, but they aren't spot meters. They both work incredibly well, so it's not an issue with no meter. Between the spot meter on my 7D and my 2 handheld meters, I'm ok, just curious about this and anyone's experience. Mightn't this be handy, with some modification and calculations, as a learning tool, perhaps? Even as a bit of an experiment in exposure calculation and lighting awareness, something can be gained.

    Based on your comment about having used an extinction meter, I take it they're slightly more than useless in most situations.

    I didn't mean to come across as someone who's just looking for the cheap way out, or something. I love learning something every chance I get, and learning the way things used to be done, helps bring home an awareness of the work that the old masters actually did. I even try to cook the old ways my folks made things, and teach my daughter some of it. Using old techniques and tools keeps our past richly alive for those who come after us to share in it.

    BTW- $50 is about 40 sheets of film, so yeah the potential for throwing money into a bonfire could be quite high!
     
  11. E. von Hoegh

    E. von Hoegh Member

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    I had a "Heyde's Aktino-photo-meter" and it was slightly better than nothing; actually it was sort of OK outside during the day once you figured out the film sensitivity scale.

    I didn't mean to offend with my comment about getting a meter, and I'm glad that you are approaching the craft(s) as you do - understanding what went before gives a more profound understanding of what we have now.:smile:

    E. (practitioner of obsolete technology) von Hoegh.
     
    Last edited by a moderator: Jan 10, 2013
  12. kintatsu

    kintatsu Member

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    I didn't take any offense, just trying to clarify interest and intent.

    I appreciate your comments and feedback. It's things like this that make joining this forum so enjoyable and valuable. I would like to find an old spotmeter that shows c/ft2, or even a more recent one showing lux. Having those values provides a nice reference when discussing our photos or planning our next shoot.

    Like I said previously, keeping the old ways alive is something I like. There seems to be a greater reward, not because they're difficult, but because you become involved. I've never tasted anything as good as my parents' homemade strawberry jam or pickles, and don't think I ever will, unless I make it with my daughter.
     
  13. E. von Hoegh

    E. von Hoegh Member

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    You can make a chart for any meter/spotmeter, calculating from LV or even EV @ ISO 100 to lux and/or foot-candles.
     
  14. johnielvis

    johnielvis Member

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    wait...this is based on someone's subjective opinion of "details", right? is that right? it's based on someone's eyeball perception? with no previous calibration to the particular person. Just so this is nice and sparkling clear--is this how it works?--the perception of the individual? Or is there some detail here that's not being seen?
     
  15. kintatsu

    kintatsu Member

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    Sorry for the delay in replying.

    I'm working on making up a quick reference for my 7D's meter now. The knowledge is there, I've just got to get it on paper! It comes in handy in determining the exposure and values for reference and for discussion, and allows us to better understand the work of those who came before us. Arbitrary EVs and the like often leave out bits that could help us share our experience, as those values and references change over time.

    As far as this method being subjective, isn't all our work? When we take readings and expose for our goal, aren't we subjecting the image our interpretation? Not to mention focusing based on our eyesight. I would think that using this method, you could replicate the detail at your desired level.

    I'm still curious to hear if anyone has used this method. Based on the comments, it doesn't seem viable or repeatable for real photos.
     
  16. kintatsu

    kintatsu Member

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    EV 10 @100 gives about 125 c/m2, which gives about 12 c/ft2. EV 11 would therefore be about 24 and so on.

    I've decided to get the Gossen Starlite 2, so things should be cool as far as that goes. C/m2 to C/ft2 is a simple conversion, so it shouldn't be an issue. I'll also have a way to verify this concept with a real spot meter and may get some kind of chart worked out for how the camera can be used as far as compensating for the human factor to some very small degree.

    The single biggest human factor, is that every time you photograph, the light may be the same, but the other variables will lead to improper perception, and ultimately a wide range of possible errors.
     
  17. Dan Henderson

    Dan Henderson Member

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    I hate to reveal my ignorance, but can someone explain the term "extinction meter" for me?
     
  18. kintatsu

    kintatsu Member

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    An extinction meter basically uses different density steps to determine the lowest level of light available. A chart is then consulted to determine exposure. They generally use letters or numbers in a progressively denser series of steps. They were a step up from the old actinic meters, using paper exposed to light.

    2 issues related to these meters relate to the ability of the eye to adapt to low light. One is the initial reading has to be made with the eye adapted to lower light, and the other is the eye becomes adapted to the point of compensating for lower light.

    I've never used one, so can't attest to how well they work, or how off they are when the eye is outside the "adapted range" of usability. Reading the old Kodak manual aroused my curiosity, and left me wondering.