DP2 Merrill sensor read noise finally measured

Started Sep 5, 2012 | Discussions thread
Truman Prevatt
Truman Prevatt Veteran Member • Posts: 6,248
Re: Do you even look at images?

Kendall Helmstetter Gelner wrote:

Truman Prevatt wrote:

Real images can fool. If you don't know the light intensity in the image, then how do you know if the DR was good or bad. You don't.

When you see a mountain scene you've seen a thousand times before, yes in fact you do.

However that's irrelevant, when a camera with known good DR (the Canon) is producing an image with apparently less DR than another camera (the Sigma). You can think of the Canon as a useful frame of reference; with default metering it was unable to capture the whole scene, so we know there was more range present than the reference camera was able to handle, so it's not like the scene was a limited subset.

Actually the Canon DR is not that good when it is put on the bench and actually measured. The top end Canons (5D MarkIII, 1D Mark Iv and 5D Mark II ) are all rated below 12. That is a good two stops below the Pentax K5. Canons are over 2.5 EV's under over the Canon's.

If you look at the calibration test on DXOMark, the Canon's are only so-so for DR. In fact the Canon flagships have less DR by about an EV than the Nikon midrange cameras, the D5100, D7000. The Canons are actually even behind the previous generation of Nikons, D700, D3s, etc. It seems clear that Sony produces a sensor with superior read noise specifications to Canons.

That's not my opinion those are the results of the an independent test lab.

While DP review does not do a test on the raw data, it does do an apples to apples against other camera. What you find on the DPreview review of the SD1 is about 3 stops below the D7000 and the SD-1 with the least DR of the other three, one from Canon, one from Sony and one from Nikon.

As far as "you know it." Over his life time Adams very seldom too a shot without carefully analyzing it with his spot meter to determine accurately the illumination distribution of the scene. There was one he didn't that was Moonrise. However, he knew exactly from previous measurements he had made that the illumination of a full moon. That allowed him to set his exposure for Moonrise.

If I am doing critical work, and what I do for myself is critical work, I normally shoot manual exposure and use my digital spot meter, not the one in a camera. I also calibrate my meter to my camera to find the correct ISO to set my spot meter at for calculating stop/shutter speed.

Quite frankly, I find myself often surprised by the illumination distribution of a scene.

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