Does it make sense? An $1800 Full frame DSLR from Canon

[Jon Ruyle]

Hi Daniel,


Thanks again. Things are clearing up for me a bit.

Okay, so you're asserting that other things being equal, read noise is inversely proportional to the square root of the size of the pixel?

How about "read noise is directly proportional to the square area"? (e- / um^2.) I think that works.

How embarrassing. I meant "read noise (in absolute terms) is directly proportional to square root of area". If read noise was directly proportional to area, high pixel density would be better (because noise adds "in quadrature", as you say... so 4 times as many pixels 1/4 the size and 1/4 the noise gives half the noise when you add it all up... 4 times as many pixels 1/4 the size but with half the noise, though, is the same.) I *think* that's right []

Read noise is indeed the much more complicated, inconsistant, and difficult to generalize. However, I think the rule is a pretty close fit to the cameras at hand.

This makes sense. I was a little baffled by the idea that there may be some reasoning with which one could come up with "read noise is proportional to square root of area".

Generally, though, one of the exceptions seems to be that when comparing tiny inexpensive digicams to large, pricey DSLR, the DSLR has less read noise at high ISO, while the very tiny pixels in the cheap digicam have less read noise at low ISO.

I'll take low read noise at high iso any day


I measured the read noise of my 5DII (not numerically, just by taking a picure and looking at it) and, as far as I can tell, it is extremely low anyway until iso is high.


The reason I measured it was that for a long time I thought there was no point in very long exposure photography: I reasoned it is better to take many images and stack (equivalent signal and noise, but far easier for a number of reasons). But then I realized read noise is worse when you stack. But after taking my dark pictures, I concluded that at iso3200 and below, read noise is pretty much negligible unless your signal size is minute.

The 5D2, for example, has very strong and objectionable pattern noise.

True, though only regularly visible by me above iso6400. At iso3200, I can't see it (in real pictures, that is). But IMO pattern noise is the worst part of very high iso images on the 5d2.

We have a lot to look forward to in the future.

Agreed. I'm very happy with my 5D2, but I think I should start saving for the 1DsX now. []