Engineered_Reflex wrote in post #18136409
One thing I'm curious about is iso 50. I've not had a camera before with iso which is expanded downwards. I can see a use for it when taking shots of say helicopters in bright conditions when I would want to keep the shutter speed low without closing the aperture too much. Is there a downside to using iso 50?
ISO 50 on recent Canons is ISO 100 gain and digitization with ISO 50 metering. If you are shooting it like slide film or JPEG-only, there should be no problem. It's as "real" an ISO 50 as slide film is. You can't, however, expect to expose to the right like you do at higher ISOs and pull back in a converter, because the "extra" headroom just isn't there.
The 5D4, however, is supposedly capable of reading out both dual-pixel halves, and the sensor has some extra headroom that Canon doesn't use, but shows when reading these half-pixels separately. In dual-pixel RAWs, one of the two is included. A firmware update from Canon, or Magic Lantern update, *could* conceivably give an ISO 50 (or at least 64) with as much headroom as ISO 100 normally has, and an ISO 25 (or 32) with the headroom that 50 currently has.
Current dual-pixel RAWs can give extra headroom, but with one small artifact: the bokeh of the extended headroom is like you covered one side of the lens, so the extra highlights will have different bokeh than the image with the lower tonal range.
This extra headroom is something you can "pull down" in a converter, and is generally not an important part of a default conversion. IOW, an OOC JPEG should not suffer from the lesser headroom, unless you have a picture style with low contrast that rolls in the extra highlights.