Dynamic Range -- what it is, what it's good for, and how much you 'need'

Started Oct 17, 2011 | Discussions thread
FrankyM
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Re: Let's put it all together.
In reply to Great Bustard, Oct 20, 2011

Great Bustard wrote:

FrankyM wrote:

If you are talking about sensors, not images, then IMO the number of pixels has nothing to do with it at all.

As I said, I'm always talking about the final photo.

If you're talking about the photos (which I always am), then it's not how an individual pixel performs, but how the pixels perform in aggregate. For example, we wouldn't compare a single 2x2 pixel to a single 1x1 pixel, but rather four 1x1 pixels.

The pixels don't 'perform in aggregate'. You process the data. Then you're comparing the results of one process with the results of another. So for example if you reduce the resolution of a 20 Mp image to 10 Mp to compare with something else, your results will depend a great deal on how you reduced that resolution.

Well, I guess this is where the diversion into semantics begins. How about this: you don't compare (in terms of the final photo) a single 2x2 pixel to a single 1x1 pixel -- you compare to four 1x1 pixels.

No, it's not a problem of semantics but understanding what exactly we are talking about. I agree with you regarding what you compare, but what I'm saying is that the processing makes a difference to the results. For example, if I reduce those 20Mp to 10 Mp by simply throwing away 1 out of every 2 pixels, the result I get will be very different to that achieved by averaging 2 pixels to 1.

Again, coming back to DR, I have no problem personally with the DxO definition as an engineer. I don't find it particularly useful though as a photographer - I would much prefer to know how many stops of highlight headroom/shadow footroom I have.

Using the noise floor as the lower limit is OK for DxO's purpose but I think that the limit for a photographer is set by a much higher SNR (my feeling is that the SNR=1 limit is too low also) and the visual characteristics of the image noise.This means that photon shot noise plays a part in DR.

But it is not because the pixels are larger per se, but rather because Canon does not yet have the capability to make the tech with smaller pixels. However, as I said, I think it has more to do with maintaining the high frame rate than the inability to make smaller pixels.

I've no idea whether Canon has the capability or not but this is not the reason they reduced the pixel count of the G11 cf. the G10.

Well, if you have no idea, then you have no idea. But I can tell you, for a fact , that more pixels for a given sensor size and efficiency results in more IQ all the way around (although this is subject to diminishing returns, of course). The only question is if the pixels can be made smaller without adversely affecting efficiency. However, the overall trend is that pixels have been getting smaller and more efficient. Of course, that's not to say that when a new technology comes out, that it might not have to begin with larger pixels.

I said I have no idea whether or not Canon has the capability to make the tech with smaller pixels. Do you have a mathematical proof for this? I would be interested if you do.

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