Quick question concerning low-light photography

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Originally Posted by Dave Humphries

I may be wrong Ed, but being pragmatic, I'd say it's the larger photosites that result in less noise that allows the manufacturers to offer what seems to be a 'more efficient' sensor (by dint of how much less they need to 'amplify' the signal at base ISO).

IIRC the effect of the larger surface area of the sensor and the bigger lens required for it mean that is largely 'cancelled out'.

No doubt I may learn something from others answering. :)

Dave

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According to the literature, the efficiency (a.k.a 'quantum efficiency') of a sensor is expressed as the ratio of captured electrons to incident photons. Usually displayed as a graph of efficiency versus wavelength, for example:

http://kronometric.org/phot/sensor/fov/F7QEinclFilt.gif

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Originally Posted by xpatUSA

Sorry, Manfred.

It stands for "Standard Output Sensitivity" first introduced by the Japanese CIPA:

http://www.cipa.jp/std/documents/e/DC-004_EN.pdf

It was incorporated into the ISO Standard 12232 as of 2006.

I understand from Doug Kerr that some later Canons use it instead of saturation-based.

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Thanks Ted. Accuracy of camera metering settingshas always been a bit of "black art" with various manufacturers (back to the film days). There has been a history of some of them being a bit liberal in their settings such as deliberately underexposing by 1/3 stop to produce more saturated negatives.

I remember reading a article somewhere (I don't have the link anymore) where different camera and light meter manufacturers effectively used anything from 12% to 18% as their baseline "middle grey".

I was recently at a workshop where we were shooting studio flash. The Nikon and Sony shooters were getting "correct" exposures when using the flash meter (based on the luminosity histogram readings), but the Canon users had to open up one stop versus what the flash meter was suggesting. I wonder if your last sentence might explain why that was happening.

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Originally Posted by Manfred M

Thanks Ted. Accuracy of camera metering settingshas always been a bit of "black art" with various manufacturers (back to the film days). There has been a history of some of them being a bit liberal in their settings such as deliberately underexposing by 1/3 stop to produce more saturated negatives.

I remember reading a article somewhere (I don't have the link anymore) where different camera and light meter manufacturers effectively used anything from 12% to 18% as their baseline "middle grey".

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Have a look here, page 13 refers:

http://dougkerr.net/Pumpkin/articles...e_Metering.pdf

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I was recently at a workshop where we were shooting studio flash. The Nikon and Sony shooters were getting "correct" exposures when using the flash meter (based on the luminosity histogram readings), but the Canon users had to open up one stop versus what the flash meter was suggesting. I wonder if your last sentence might explain why that was happening.

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Can't find Kerr's take on that (it's buried somewhere on my HD) but I'd guess that the Nikon and Sony shooters were either SOS or REI*** where the camera metering gives less headroom (at the sensor) and maybe the Canonistas were toting older models, as they do ;)

*** Yet another ISO definition - the worst of them all, IMHO. Based on their own comprehensive testing, the manufacturer is allowed to pass an opinion as to what is best for you. You can imagine my opinion about that ... :(

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Originally Posted by xpatUSA

Can't find Kerr's take on that (it's buried somewhere on my HD)

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Found it, Manfred:

"For Canon digital SLR cameras, we get some insight into what has been done from an exposure control test recommended by Canon. It implies that the “standard exposure” planned for these cameras is about 17.3% of saturation exposure.

We believe that for these cameras the exposure meter calibration itself is closely in line with ISO 2721. Thus, we must conclude that Canon has rated the “ISO sensitivity” of their sensor systems at about 74% of what would be determined in accordance with ISO 12232—that is, a sensitivity that Canon rates 'ISO 100' would probably be rated as ISO 135 if actually determined in accordance with ISO 12232."

For what it's worth ...

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Originally Posted by xpatUSA

Found it, Manfred:

"For Canon digital SLR cameras, we get some insight into what has been done from an exposure control test recommended by Canon. It implies that the “standard exposure” planned for these cameras is about 17.3% of saturation exposure.

We believe that for these cameras the exposure meter calibration itself is closely in line with ISO 2721. Thus, we must conclude that Canon has rated the “ISO sensitivity” of their sensor systems at about 74% of what would be determined in accordance with ISO 12232—that is, a sensitivity that Canon rates 'ISO 100' would probably be rated as ISO 135 if actually determined in accordance with ISO 12232."

For what it's worth ...

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Interesting, but not enough to explain the difference we were seeing. The Nikon / Sony shooters were running at f/11 and the Canon shooters had to go up to f/8 to get the same histogram (at the same focal length and ISO setting). Shutter speed was irrelevant as we were shooting in a studio, with studio flash.