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  1. #11

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    Ahh... I've finally glommed on to a graph of the sensitivity of a CdS cell. Look at this, it's astounding. If this is the truth, then many built-in 35mm meters can be WAY off in different kinds of light.Click image for larger version. 

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  2. #12

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    Quote Originally Posted by Tom1956 View Post
    Ahh... I've finally glommed on to a graph of the sensitivity of a CdS cell. Look at this, it's astounding. If this is the truth, then many built-in 35mm meters can be WAY off in different kinds of light.Click image for larger version. 

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    Hi Tom

    Yes...
    Only the CdS cell (probably the left graph - Im on a phone) was used in cameras and light meters until superceded by silicon cells.
    The CdS meters would work in moon light and their response could be improved by a tailored filter, like Leica M8s needed.
    People used to use tables, then Selenium, then CdS, ... etc., they work good in 98 % of most peoples shots.
    You need to understand their limits for the other 2%.
    I still use a table and a Selenium.
    Before tylight I'm ODing on latte and muffins, in a WiFi cafe.
    Ansell used Selenium but his phots are better then mine.
    Dont forget about the mercury battery problem... and CdS aging...

    Noel

  3. #13
    RalphLambrecht's Avatar
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    Quote Originally Posted by dorff View Post
    Well, the obvious goal is to match the spectral response of the film and the meter..
    Is it?or ;if you believein and work withprevisualization is it the match betweeneye and meter?
    Regards

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

  4. #14
    Bill Burk's Avatar
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    Ralph, you're right.

    Visualizing - making what your mind sees... understand what spectrum your eyes are sensitive to, understand the spectral sensitivity of the film. And understand the meter's sensitivity.

    Throw filters into the mix and you have four different charts to comprehend.

    Boggles the mind if you let it. But my favorite approach is to consider the "folklore" of photography advice, and see how it fits in with the specific combination I am using.

    Then it becomes fun. I can bring out my Weston Master II and see the world in a different light.

  5. #15
    Sirius Glass's Avatar
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    Quote Originally Posted by Tom1956 View Post
    Ahh... I've finally glommed on to a graph of the sensitivity of a CdS cell. Look at this, it's astounding. If this is the truth, then many built-in 35mm meters can be WAY off in different kinds of light.Click image for larger version. 

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    This aligns with what I remember about CdS meters. They were blue sensitive and not so good for reds or IR film.
    Warning!! Handling a Hasselblad can be harmful to your financial well being!

    Nothing beats a great piece of glass!

    I leave the digital work for the urologists and proctologists.

  6. #16

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    I always thought that the obvious goal was to understand any significant interactions between the spectral response of a meter and the color of light, scene, and filter to best determine the desired exposure values. Some would call that 'visualization". I call it "anti-formularization" but that lacks panache and doesn't roll off the tongue as good.

  7. #17

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    p.s. I'm with Bill B on the "folklore" and tribal wisdom. Between that, the proven smarts of the camera/meter manufacturers (in most cases), and the smarts of a smart photographer it is possible to make good images without dissecting the minutia of engineering details surrounding well-proven historical equipment. Not that that can't be interesting, of course.

  8. #18

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    Quote Originally Posted by BrianShaw View Post
    p.s. I'm with Bill B on the "folklore" and tribal wisdom. Between that, the proven smarts of the camera/meter manufacturers (in most cases), and the smarts of a smart photographer it is possible to make good images without dissecting the minutia of engineering details surrounding well-proven historical equipment. Not that that can't be interesting, of course.
    Ignorant barbarians insensitive to the fine points (that's me) just use their equipment as directed and nearly always get good results (technically, not artistically).

    I've hit only two situations out-of-doors where having a color temperature meter and CC filters might have been useful, and then only with color film. Once upon a time in the Big Cypress at the Sweetwater Strand ... I shot an alligator in deep shade. Nikon FM2n, ISO 100 E6. Roses are red, gators are blue, and my little blue gator was well-exposed. Score one for Nikon. Once upon a time in my backyard I was trying out a B&L Tessar IIb. Acceptance testing, done with ISO 100 E6 in a N8008S. When I took the test shots the sun was behind a cloud. White subject came out a well-exposed blue. Same problem as my little blue gator. Score one for Nikon. On retest with the sun not hidden behind a cloud the blue cast didn't appear.

    When my LunaPro (= LunaSix III) and Master V were both freshly calibrated they never agreed exactly. No matter which I followed I usually got good exposures on E6. The exception was with a 160/5.6 Pro Raptar in the infamous blue-faced Rapax, top speed 1/200. Turns out that the shutter ran very very slow at its top three speeds.

    In other words, some posters here worry too much and test too little.

  9. #19

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    I'm not sure I'm gleaning what I had hoped from starting the thread. Specifically, shouldn't I start paying more attention to making allowance in my camera settings for other color temperatures of lighting than daylight, for which it is understood the film speeds are dialed in for on the meter dial? Look again at the sharp cut-off in the graph for color temps outside the peak. Until I began this research I had no idea meter cells were THIS peaked in their sensitivity. They quickly become downright insensitive outside this peak.

  10. #20
    Bill Burk's Avatar
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    Hi Tom1956,

    The vendor's chart you found seems to illustrate three different products they offer, which seem to be designed to peak at different colors.

    The reference I found in Todd-Zakia Sensitometry gives a single CdS curve, probably an average of cells available at the time, that is a little less abrupt...

    It seems to indicate CdS has 80% sensitivity or more over the range from blue to orange.

    And then the Weston (I assume Selenium Solar Cells) leans slightly more into the red.

    Folklore-wise, that tells me to use a "Tungsten" rating when evaluating indoor incandescent exposure with a Selenium-based meter.

    And it would also tell me when using that meter, I would be better off to meter without a filter and then apply a filter factor when using a deep red filter.

    And I think that will help you avoid underexposed negatives when using a deep red filter... Which is what I think should be your primary concern... It is mine.


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