I give up....
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can you boys read?
By the way, underexposing at lower ISO is precisely what Canon cameras do in the raw data when Highlight Tone Priority (HTP) is enabled; and what Nikon cameras do when Active D-Lighting (ADL) is enabled. Instead of using the ISO gain set by the user, the camera uses a lower ISO (but exposes with the indicated aperture and shutter speed), effectively underexposing the image; this provides more highlight headroom. In post-processing, the image data can be brought back up while preserving the highlights with a modified tone curve in higher exposure zones. The place where image quality suffers is in shadows at lower ISO, precisely as the above quantitative model predicts.
We could not tell any difference, apart from the DoF.
He's [...] incorrect about HTP being a linear doubling (HTP processing is application of a tone curve to boost the shadows and midtones but not the highlights).
There are certain situations where a crop delivers higher resolution than a FF with the same lens (even disregarding DoF, AF and the corners). Roger M. Clark has nice shots of the moon with the 5D2 and the 7D that show this:
The sensor does not care about iso, iso step is added after the readout.
no they are not
At 100iso with the same metering the sensor charge is under 100 % and at the read out =before overload and clipping
with 50iso your double the time or open up the lens 1 stop and therefore blow one stop of highlight.
I don't know if ACR / Lightroom does that, but most tools based off DCRAW do. I'd especially recommend Raw Photo Processor
I'm afraid I'm running good ol' Windows so that tool would be only available in a MacOSX vm and I doubt it'd be worth the hassle, esp. since I'd end up having a demosaiced 100mb tif instead of a 20mb raw dng.
But I'm hopeful that in LR's raw processing adjusting the exposure doesn't collide with tone curves either applied manually or via picture styles.
(I)f I understand you correctly you're saying that if the postprocessing software is capable of operating in raw space iso50 should be equal to ettr @iso100?
so regarding of the subject (motive with no high lights = motive with a small DR) you can overexpose and get a benefit of the over exposure in the shadows
That's great information, thanks! I'll certainly use that once I've got a 6d and am doing tripod macro focus stacks with low dr objects.
Expanded ISO means digital gain (negative gain for ISO 50). The exposure is at ISO 100, then pulled down a stop. In your example, you'd lose the highlights.