octo wrote: 1) Those are the real ISO values: all the (power 2) x 100 ISOs are exact (200, 400, 800, 1600, 3200 ... 51200) because they're full stops. The ones that are not exact are not (powers of 2) x 100, because they're either a third of a stop, or 2 thirds, and due to Math ... Pow(2, 2 + 1/3) * 100 => 503.9, and not 500 => 503 is correct, and 500 is shown in camera but actually it's really 503. Same for 251.9, etc.
Ah, I see. I should have figured that out.
So, this is still only values taken from the camera settings then? Not something measured, kind of true value or exposed and developed the same way? Of course, I don't know if it technically would be possible to compare that way... What I'm trying to say is that if the ISO values in the graphs just are what respectively camera says it is I would find it hard to believe in them.
Ah, OK. But, however it is done, applying some kind of noise reduction to raw files seems as a stupid idea.
On the site somewhere Bill Claff, discusses why he uses the camera's reported ISO rather than measured ISO, but I can't find it right now. I could find this analysis in which he did a study of DXO's measured ISOs vs. camera settings for ISO here:
And basically he find most cameras are off by about a third of a stop and he believes that is to protect highlights and not to game the system by falsifying ISO. Basically, I think he is suggesting that the camera values are a good place to start and that measuring ISO wouldn't change things much, but I may be distorting his argument.
octo wrote: 1) Those are the real ISO values: all the (power 2) x 100 ISOs are exact (200, 400, 800, 1600, 3200 ... 51200) because they're full stops. The ones that are not exact are not (powers of 2) x 100, because they're either a third of a stop, or 2 thirds, and due to Math ... Pow(2, 2 + 1/3) * 100 => 503.9, and not 500 => 503 is correct, and 500 is shown in camera but actually it's really 503. Same for 251.9, etc.
Ah, I see. I should have figured that out.
So, this is still only values taken from the camera settings then? Not something measured, kind of true value or exposed and developed the same way? Of course, I don't know if it technically would be possible to compare that way... What I'm trying to say is that if the ISO values in the graphs just are what respectively camera says it is I would find it hard to believe in them.
Ah, OK. But, however it is done, applying some kind of noise reduction to raw files seems as a stupid idea.
On the site somewhere Bill Claff, discusses why he uses the camera's reported ISO rather than measured ISO, but I can't find it right not. I could find this analysis in which he did a study of DXO's measured ISOs vs. camera settings for ISO here:
And basically he find most cameras are off by about a third of a stop and he believes that is to protect highlights and not to game the system by falsifying ISO. Basically, I think he is suggesting that the camera values are a good place to start and that measuring ISO wouldn't change things much, but I may be distorting his argument.
Dec 25, 2024 at 02:08 PM
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