Olympus OM-D (EM-5) comparison samples are now.. (continued)

Started Mar 17, 2012 | Discussions thread
bobn2
bobn2 Forum Pro • Posts: 61,073
Re: Olympus OM-D (EM-5) comparison samples are now.. (continued)

Andy Westlake wrote:

Simon Cowell wrote:

Based on the answer above, how valid is it to present the comparison results in terms of the manufacturers's ISO settings when it is known that the ISO 12232:2006 standard allows the manufacturers to set the ISO values arbitrarily

That's something of a misapprehension. While the REI definition within ISO12232:2006 sort-of says that, our testing is essentially based on using the Standard Output Specification definition.

But what matters is not what your testing is based on, but how the manufacturers have set up their cameras.

That's what we report on, and that's how all of our tests are conducted. Most cameras conform to it pretty well in practice.

But, if they don't, then your test method fails. I think you are in a circular argument here. While modern cameras must use REI, because they have multi pattern metering, your test assumes that they conform to SOS. You assume that they do conform to SOS because that's your test method. You are using (approximately) constant lighting, which, if all cameras conform to SOS would lead to the same EV setting to give the same exposure, yet you get very different EV values. What does that tell you?

and is applicable to sRGB output (not raw) only?

How does it make any sense to suggest a camera has a different ISO setting dependent upon whether you're shooting RAW or JPEG? The camera doesn't change its metering or anything when you change file format or color space.

Strictly, it hasn't an 'ISO' setting in raw at all. But you are forced to make the assumption that the ISO setting is the same because of that first assumption that the camera is calibrated to SOS. If you were, as you should be, testing cameras at the same exposure , ISO for ISO, then you will have no problem making the link back to raw. All you'll be saying is that for this (ISO nominal exposure) and this (camera) ISO setting, these are the results that the camera produces.

We test ISO, essentially according to the SOS method, and present the results in every review.

You are testing meter calibration there. Different thing from sensor response.

All of our further tests are implicitly based upon that, because they're exposed so particular reference grey patches are rendered at a standard brightness. You do need to pay attention to those ISO test results when comparing cameras .

If your test procedure was sound, then all cameras at the same ISO would be tested with the same exposure. Clearly they is not happening. So, you have a problem with your procedure.
--
Bob

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