ISOless sensors, read noise and photography - many questions!

Started Oct 3, 2013 | Discussions thread
RussellInCincinnati
Senior MemberPosts: 3,197
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so just use an ISO a stop or two below what's "needed"
In reply to Steen Bay, Oct 31, 2013

Steen Bay wrote: Note that the graphs in the OP are a bit inaccurate at the highest ISO settings. If a camera has reached its lowest read noise (e-) at for example ISO 800, then the read noise will be the same at higher ISOs. The read noise will always decrease or remain the same if the ISO is increased, it'll never be higher at a higher ISO than it was at a lower ISO.

Now that you mention it, that must be true. Because why would the manufacturer do anything to the camera to increase its read noise at increasingly high ISO's? Wouldn't make sense. Guess the very slight bounce upward in read noise in the original post graphs is simply "noise in the data" or measurement drift. Thanks for pointing this out, it seems obvious now.

So with your observation, if you want to preserve highlights and get rid of the need for bracketing above ISO 800 on a Nex C3, all you have to do is make sure you're using an ISO that's 800 or higher, but still lower than what you need for a perfect electronic viewfinder preview and playback. By that logic, if need to take a Nex C3 raw picture at ISO 25600, leaving the ISO at 6400 would eliminate the need for bracketing, preserve highlights, and be "just as good" as leaving the ISO at 800. And by setting an ISO just a stop or two lower than what you "need", ISO 6400, for a good viewfinder image, leaves you with an usable viewfinder image without being pointlessly dim ISO 800.

Point well taken. To recap, in the field when you need a photo above ISO 800, set the camera to an ISO at least 1 and perhaps 2 stops lower than what you think is indicated. Viewfinder will still be usable, and you can fix the ISO in raw post-processing.

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