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#11
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Alan Browne wrote in news:_ZqYc.14049
: From time to time you will see postings that suggest the manufacturers do not follow the ISO sensitivity very well. Yepp - the ISO sensitivity for film is rather easy to define. You can build a brand independent test equipment for the film you want to test. There are differnet definitions for negative and positive film though. But - how do you test that a digital camera follows the ISO specification? Compact digital cameras have a non removable lens. How do you know what F-stop the camera really chooses? How are you sure that the camera really chooses the correct exposure time? Then - a digital camera may make some "hokus pokus" when doing the actual translation from charges to digital values, and it probably does. It might apply some levelling of the values before converting to e.g. JPEG. Now - you can of course test wether the camera's exposure meassurement system gives the same result as a well callibrated exposure meter. But, cameras have never been so good att doing that - that was the case even for film based cameras. And, even worse, modern cameras have some kind of "intelligent" exposure meassurement, evaluating the picture. Now we are talking about serious "hokus pokus". So - in short. Yes there might be problems with what the camera call ISO 100. The G2 I have have ISO 50. Most other compact dicicams have ISO 100 as lowest. But tests - e.g. at www.dpreview.com - shows that this is the same sensitivity. So - either G2 lies about being too bad or the other lying about being too good. What do you think is the case? /Roland |
#12
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"David J. Littleboy" wrote in
: Does the "sunny 16" exposure rule apply to digicams? Yes. No. It applies to negative films where there's enough latitude that the printer can rescue your incorrect exposures. It's advisable to use the meter (and the histogram) with slide films and digital cameras, or with negative films if you care about getting the most from the film. The sunny 16 rule is very dependable in bright sunshine as our Sun is a very dependable source of light. If it was not, we would be in great trouble. Of course, a meeter is needed for the shadows. But for well lit parts, nope not at all. /Roland |
#13
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"David J. Littleboy" wrote in
: Does the "sunny 16" exposure rule apply to digicams? Yes. No. It applies to negative films where there's enough latitude that the printer can rescue your incorrect exposures. It's advisable to use the meter (and the histogram) with slide films and digital cameras, or with negative films if you care about getting the most from the film. The sunny 16 rule is very dependable in bright sunshine as our Sun is a very dependable source of light. If it was not, we would be in great trouble. Of course, a meeter is needed for the shadows. But for well lit parts, nope not at all. /Roland |
#14
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"Roland Karlsson" wrote
The sunny 16 rule is very dependable in bright sunshine as our Sun is a very dependable source of light. If it was not, we would be in great trouble. Well, the brightness of the sun at the Earth isn't a constant. It's 7% brighter in January than in July (the Earth is 3.5% closer to the sun in January). Might not make much of a difference to what shutter speed you use, but it's just one variable (among many other more important ones) that can vary the intensity of sunlight in a picture. |
#15
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"Roland Karlsson" wrote
The sunny 16 rule is very dependable in bright sunshine as our Sun is a very dependable source of light. If it was not, we would be in great trouble. Well, the brightness of the sun at the Earth isn't a constant. It's 7% brighter in January than in July (the Earth is 3.5% closer to the sun in January). Might not make much of a difference to what shutter speed you use, but it's just one variable (among many other more important ones) that can vary the intensity of sunlight in a picture. |
#16
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Roland Karlsson wrote:
Now - you can of course test wether the camera's exposure meassurement system gives the same result as a well callibrated exposure meter. But, cameras have never been so good att doing that - that was the case even for film based cameras. And, even worse, modern cameras have some kind of "intelligent" exposure meassurement, evaluating the picture. Now we are talking about serious "hokus pokus". For one thing, I would expect that if I light a grey card such that an incident meter gives me a reading (let's say f/5.6 @ 1/15) and that I shoot the the image with that setting... when I look at the image rgb channels, they should: 1) each show an equal level (or very nearly so) (R=G=B) AND that level should be 18% grey... which according to at least http://astro.umsystem.edu/apml/ARCHI.../msg00561.html is R=G=B=115 (scale of 0..255). (One fellow in the link above scanned a grey card and got 121,121,121 which is pretty close). http://www.aim-dtp.net/aim/calibration/middle_gray/ near bottom suggests that the mid point (R=G=B=128) is the correct value. In any case, if R,G,B are each in the range 110 - 130 for a properly exposed shot of a grey card, then it is likely the metering of the camera is correct. Cheers, Alan -- -- rec.photo.equipment.35mm user resource: -- http://www.aliasimages.com/rpe35mmur.htm -- e-meil: there's no such thing as a FreeLunch.-- |
#17
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"Ken Scharf" wrote in message . .. Does the "sunny 16" exposure rule apply to digicams? Only as a rough guide. You will discover that it is often too dark with either digital or slide film. You'll have to experiement with your camera. As for my 10D, 16 is usually too dark. F11 is closer--but then it varies a lot due to atmospheric conditions and other factors. |
#18
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"Ken Scharf" wrote in message . .. Does the "sunny 16" exposure rule apply to digicams? Only as a rough guide. You will discover that it is often too dark with either digital or slide film. You'll have to experiement with your camera. As for my 10D, 16 is usually too dark. F11 is closer--but then it varies a lot due to atmospheric conditions and other factors. |
#19
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"Roland Karlsson" wrote in message ... "David J. Littleboy" wrote in : Does the "sunny 16" exposure rule apply to digicams? Yes. No. It applies to negative films where there's enough latitude that the printer can rescue your incorrect exposures. It's advisable to use the meter (and the histogram) with slide films and digital cameras, or with negative films if you care about getting the most from the film. The sunny 16 rule is very dependable in bright sunshine as our Sun is a very dependable source of light. If it was not, we would be in great trouble. If you care about your exposures, you'll find that Sunny 16 is rarely correct. Of course, a meeter is needed for the shadows. But for well lit parts, nope not at all. It's not just shadows: sunny 16 simply is simply wrong too much of the time to use for slides and digital. David J. Littleboy Tokyo, Japan |
#20
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"Roland Karlsson" wrote in message ... "David J. Littleboy" wrote in : Does the "sunny 16" exposure rule apply to digicams? Yes. No. It applies to negative films where there's enough latitude that the printer can rescue your incorrect exposures. It's advisable to use the meter (and the histogram) with slide films and digital cameras, or with negative films if you care about getting the most from the film. The sunny 16 rule is very dependable in bright sunshine as our Sun is a very dependable source of light. If it was not, we would be in great trouble. If you care about your exposures, you'll find that Sunny 16 is rarely correct. Of course, a meeter is needed for the shadows. But for well lit parts, nope not at all. It's not just shadows: sunny 16 simply is simply wrong too much of the time to use for slides and digital. David J. Littleboy Tokyo, Japan |
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