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  1. #11
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    WayneF's Avatar

    Re: Photography stops

    Quote Originally Posted by Vincent View Post
    I talked to an oldie in the trade and he stated that the diaporama develpment on film did not have a lot of latitude, you needed a meter since being wrong will lead to not usable results.
    Reversal film (slides) don't have much latitude, but negative film had very wide latitude, if given enough exposure. That allowed Sunny 16 to work well for negatives, the dark room processing took care of the rest of it then.

    Kodak used to specify the ASA film speed of B&W negative film as half of what it actually was, for greater insurance against underexposure (in regard to Sunny 16). But in 1960, they doubled the speed rating of all their B&W negative film, since light meters were becoming more available, and meters even had started appearing built into cameras (Nikon F had no meter until 1963). No internet then, camera magazines carried most communication, and you should have seen the articles protesting meters in cameras... are we going to let our camera tell us what to do? How could a meter in the camera possibly be accurate? Same old fogy nonsense that accompanies any new technology.

    Quote Originally Posted by Stoshowicz View Post
    I always wondered why the camera couldn't expressly function as an absolute light meter rather than meter relative to exposure.
    Camera meters can read reflected light from the subject. It can be absolute in that sense. But the one in a cell phone is not in the same class as the one in a DSLR. DSLR have very special purpose meter cells built- into the viewfinder, designed for the job. Compacts and cellphone (and Live View) can only just look at some pixels in the image.


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  2. #12
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    fotojack's Avatar

    Re: Photography stops

    Quote Originally Posted by sonicbuffalo View Post
    I still can't figure out what you're saying

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  3. #13
    Happy to be Canadian
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    Marcel's Avatar

    Re: Photography stops

    Of course you can learn to do away without the light meter, the same way as you can drive a car without a speedometer. But I, for sure, wouldn't want to drive from Chicago to Los Angeles without a cruise control.

    I really wonder what you are trying to prove.
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  4. #14
    Senior Member
    Stoshowicz's Avatar

    Re: Photography stops

    [QUOTE=
    Camera meters can read reflected light from the subject. It can be absolute in that sense. But the one in a cell phone is not in the same class as the one in a DSLR. DSLR have very special purpose meter cells built- into the viewfinder, designed for the job. Compacts and cellphone (and Live View) can only just look at some pixels in the image.[/QUOTE]


    Well Im meaning absolute in terms of , ummm, the camera already calculates how much light is coming into a sensor based on a voltage accumulated over a period of time, knowing aperture and ISO,,
    Then it calculates whether that would be over or under exposed at the settings you chose.
    It seems that it should be able instead to calculate the brightness of the scene and just tell me THAT- instead of changing the output 'relative value' with each click of aperture speed or change of ISO. I could then do a sweep of my circumstance , get a basic idea of how bright the scene is irrespective of my settings , and then I could go right to whatever settings I like to use, I wouldnt have to do clicks up and down from a floating exposure value. Im in accord with the old school guys, almost never use automated exposures and half the time never even consult the meter.

    The camera appears to have the data , they just don't program it to inform in this manner.
    Last edited by Stoshowicz; 12-24-2014 at 01:46 PM.

  5. #15
    Senior Member
    Horoscope Fish's Avatar

    Re: Photography stops

    Quote Originally Posted by Stoshowicz View Post
    It seems that it should be able instead to calculate the brightness of the scene and just tell me THAT - instead of changing the output 'relative value' with each click of aperture speed or change of ISO. I could then do a sweep of my circumstance, get a basic idea of how bright the scene is irrespective of my settings...
    Are you asking why the camera's meter doesn't measure incidental light, like a hand-held light meter does, as opposed to measuring reflected light?

    I ask because the in-camera light meter *does* calculate the "brightness of the scene"; it calculates the brightness of the *entire* scene and then averages everything to expose properly at middle grey.

    ...
    Last edited by Horoscope Fish; 12-24-2014 at 02:01 PM.
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  6. #16
    Senior Member
    WayneF's Avatar

    Re: Photography stops

    Quote Originally Posted by Horoscope Fish View Post
    Are you asking why the camera's meter doesn't measure incidental light, like a hand-held light meter does, as opposed to measuring reflected light?

    I ask because the in-camera light meter *does* calculate the "brightness of the scene"; it calculates the brightness of the *entire* scene and then averages everything to expose properly at middle grey.

    ...

    I am in full agreement. Just elaborating.

    Probably very few beginners ever heard of an incident meter, so it seems important to explain. Camera meters are reflected meters (sees light reflected by the subject). Most Sekonic hand held meters can also meter incident light (sees direct light incident onto the subject). There have been early handheld reflected meters, but today, when one says "hand held meter", they most likely infer incident meter.

    Incident meters also seek a middle gray level, same as reflected meters do. That is all any light meter can do, they are just a dumb chip with no knowledge of what the subject is, or what the readings mean. No experienced human brain to think it out. That's what we use the photographer for.

    Reflected meters see very little light is reflected from the black dress, so they boost it to middle (which is overexposure). Reflected meters see a lot of light reflected from the white dress, so they pull it back to middle (which is underexposure). Both dresses come out gray. Neither is correct.

    But incident meters read the light directly, which means black dresses come out black, and white dresses come out white, relative to that gray midpoint.

    Incident meters are aimed the other direction, away from the subject towards the camera and the light source, so the subjects colors do not affect its reading. It literally measures the light. But reflected meters only see what the subjects colors can reflect.

    Surely incident meters could be built into cameras, but incident has to be metered at the subject, to see the specific light actually on that subject. Handheld meters are greatly more convenient for that.

    How Camera Light Meters Work
    Last edited by WayneF; 12-24-2014 at 07:26 PM.
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  7. #17
    Senior Member
    Challenge Team
    Eyelight's Avatar

    Re: Photography stops

    Quote Originally Posted by Horoscope Fish View Post
    That's called Exposure Reciprocity and it's one of the basic rules that used to be taught to photographers some years ago. The concept seems to baffle many but as you correctly point out once we establish a base-line for proper exposure we can adjust our settings and *know* our exposure is still correct while controlling depth of field (aperture), motion blur (shutter speed) and digital noise/grain (ISO).

    Using Sunny 16 as our baseline we know f/16 @ 1/125 (Sunny 16) = f/8 @ 1/250 = f/5.6 @1/500 = f4/@1/1000 = f/2.8 @1/2000 etc. etc. etc.

    We can do the same thing with ISO. If use "Sunny 16" at ISO 400 then f/16 @ 1/400 = f/8 @ 1/800 = f5.6 @ 1/1600 = f/4 @ 1/3200 etc. etc. etc.

    Of course now we all have preview LCD's and histograms so these base skills are becoming a sort of Lost Art.

    ....
    I can do this quicker with camera in hand, as I'm suspecting you can too. But, I think we missed f/11. Yes??
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  8. #18
    Senior Member
    Horoscope Fish's Avatar

    Re: Photography stops

    Quote Originally Posted by Eyelight View Post
    I can do this quicker with camera in hand, as I'm suspecting you can too. But, I think we missed f/11. Yes??
    That... Uh... That was a test. Glad to see you're paying attention!

    *cough, cough*

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  9. #19
    Senior Member
    Challenge Team
    Eyelight's Avatar

    Re: Photography stops

    Quote Originally Posted by Horoscope Fish View Post
    That... Uh... That was a test. Glad to see you're paying attention! *cough, cough* ....
    I appreciate your effort keeping me on my game. Every bit helps.
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  10. #20
    Senior Member
    Challenge Team
    Eyelight's Avatar

    Re: Photography stops

    There is a very slight off target in the OP related to the use of EV.

    EV is derived by a calculation that does not consider ISO or lighting . It is used to compare camera settings independent of actual light or film ISO (or digital sensor ISO sensitivity). So, aperture/shutter combinations that yield the same EV will yield the same exposure at the same ISO, but EV does not carry up or down ISO sensitivity. An EV of 15 would only be appropriate for bright sun at ISO 100.

    Quote Originally Posted by Vincent View Post
    So normal sunlight is also EV15 ISO200 1/2000s f5.6 or EV15 ISO100 1/500s f8.
    1/2000 @ f/5.6 yields an EV of 16
    1/500 @ f/8 yields an EV of 15

    These EV values will always be the same whether at ISO 100, 200, 400, etc. And what this tells us is that the two combinations are 1 stop apart. Easier to see here because the shutter speed is 2 stops difference (double-double) and the aperture is only 1 (half).

    Just remember EV is about shutter/aperture combinations. EV15, for instance, represents a series of equivalent combinations and only at ISO 100, all these combinations would yield an exposure appropriate for the proverbial Sunny 16 daylight shot. If you changed the ISO to 200 your EV (aperture/shutter combinations) would change to EV16 to yield the same Sunny 16 exposure. If you changed to ISO 800, your EV would change to EV18 (3 stops from EV15) to yield the same Sunny 16 exposure.
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