What I learned from Gollywop -- and what I wonder

Started Mar 26, 2013 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: What I learned from Gollywop -- and what I wonder

texinwien wrote:

Anders W wrote:

texinwien wrote:

It will, however, also net you less dynamic range, tonal range and color sensitivity. That's where the tradeoff comes into play with this strategy. You have to decide whether the drop in read noise is worth the tradeoff in the loss of dynamic range, tonal range and color sensitivity that comes along with it (when bumping ISO from 200 to 400 on the E-M5 and keeping exposure the same, as an example).

But you are wrong here. Going from ISO 200 to 400 on the E-M5 under these circumstances (where, importantly, you cannot increase exposure any further and you are still at least one EV short of the clipping point if you stay at base ISO) will bring you only advantages (significantly lower read noise, and thus significantly lower shadow noise), no disadvantages.

Exactly - thanks for pointing this error out and offering a clear and concise correction. I don't want to be guilty of muddying the waters on an already complex topic.

What you must keep in mind here is that the DxO figures for dynamic range, tonal range, and color sensitivity are for a sensor exposed up to the clipping point. If you are below that point, the figures are correspondingly lower.

Funny enough, I pointed out this same error in another poster's reasoning last week. Now I'm guilty of it, myself. Not sure what it is about this topic that makes it such a minefield  

I don't really think that's a mystery either. The subject is simply complex in the sense that there are many variables/parameters involved and there is quite a bit to know, and keep in mind, about each of them. Hence, the likelihood of logical slip-ups increases signficantly.

Practice makes perfect though. That's why it is important to think and talk about it. Some people are wont to say that "theoretical" discussions of the present kind are of no help in the field. I think it's exactly the other way. Only by thinking and talking about it will you eventually know exactly what to do in the field, and do so intuitively and instantly. For example, I know "without thinking" when it's the proper time to switch from ISO 200 to ISO 400 on my E-M5 when I am out taking pictures. But I do so only because I have exercised my thinking about the matter quite a bit beforehand.

What you must also keep in mind is that things like dynamic range, tonal range, and color response are not distinct from noise. They are just different ways to index noise. We need multiple measures of noise because, as with pretty much any attempt to reduce a complex reality into a single number, none of them tells us everything we might want to know.

Thanks for the helpful explanation.


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