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 19, 2011

Great Bustard wrote:

FrankyM wrote:

Well read what he does say -

That helps us in terms of light capturing ability and increases the signal to noise ratio. In turn, that does nothing but help the dynamic range of the camera. '

Well, with a fair bit of twisting, you could make that statement true. One could say that a new, more efficient, design could not be made with smaller pixels at the current time, thus the larger pixels give more DR than smaller pixels. This gives the impression that the greater DR is a result of larger pixels rather than a more effiicent sensor with new tech. This is also likely the answer to the Canon G12 question you pose further below.

But for a given sensor efficiency , larger pixels have no DR advantage over smaller pixels.

If you're talking about sensors, pixel noise performance is what it's about.

Not at all -- the number of pixels is also a key player. If the pixels can be made so that the read noise and saturation scale with the area of the pixel (equally efficient), then smaller pixels are always better (in terms of IQ).

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

If the smaller pixels cannot be made as efficient, then depending on the difference in the number of pixels and the difference in efficiency, smaller pixels will have an advantage in some circumstances, and larger pixels will have an advantage in others.

If you're talking about photos then it depends also on the processes followed after image capture. However, image SNR cannot be more than pixel SNR at the same resolution.

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.

And, as I've said elsewhere in this thread, the DR is the number of stops from the noise floor to the saturation limit. Smaller pixels have both lower noise floors and lower saturation limits, which are in proportion to the pixel area for a given efficiency, so the DR / pixel remains unchanged.

I'm not arguing the definition of DR, merely pointing out that what you say is in disagreement with Canon's spokesman.

Of course, "Canon's spokesman" is going to put a positive spin on every choice Canon makes. Now, as I've said, perhaps Canon is using a new tech, and it couldn't be made with more pixels at this time, and it indeed does have a significant advantage over an older tech with more pixels.

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.

Doesn't Chuck Westfall work as a marketing representative for Canon? He would be no more interested in hearing that smaller pixels have no IQ advantage than hearing that lens IS has no advantage over sensor IS.

I don't know who Chuck Westfall is but his title is given as "Technical Advisor in Canon USA's Pro Engineering and Solutions Division" by DPR. It doesn't sound like marketing to me.

Perhaps "US advisors sent to Uganda" doesn't sound like "fully armed soldiers" to you, either.

Perhaps it doesn't but it's not much of an argument...

Then I misunderstood you. I consider that a 'technical' rather than operational consideration (normally operational refers to the actual operation of a business - so if, for example, not enough 36mp sensors could be manufactured in time for a fixed date product launch, that would be an operational reason to go with something else).

I call anything that involves the operation of the camera as "operational", e.g. AF, frame rate, etc.

Nevertheless, that's just conjecture on your part.

Of course -- it's not as if Canon sent me the specs and asked my advice. But, my "conjecture" is based on solid, and well understood, principles.

You may be right but it's still conjecture.

Well the history with their G series is one of increasing pixels and then decreasing them. So the question is why?

I hope my explanation above (first paragraph) answered that question to your satisfaction.

Well, thanks for trying...

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