more pixels are better!

Started Dec 14, 2008 | Discussions thread
ejmartin Veteran Member • Posts: 6,274
Re: SNR vs exposure

Graystar wrote:

ejmartin wrote:

There is definitely an error in the ISO calibration of DxO's data for
the LX3. My own measurements...

I see. They're wrong because you're right. Got it.

It's not just that I happen to have done independent quantitative testing (and that I also checked the ISO calibration of the LX3 against a 1D3 and 1Ds3, though not under as controlled a laboratory situation as DxO uses). It's just common sense.

Digicams have 1-3 stops worse S/N performance than DSLR's. If they were to normalize their ISO calibration the same as DSLR's, they would leave about 3-3.5 stops of the DR in highlights. Instead, typical digicams leave about 2.5 stops of headroom, so that they can devote more of what little DR they have to better performance in shadows. This is why it's so much easier to blow highlights on a digicam if you trust the metering, and why many digicam users have found they get better results if they apply at least -1/3 EC to the metering.

Now look at the DxO ISO calibration test for the G10 and LX3 in comparison to say the 1D3:

http://www.dxomark.com/index.php/eng/Image-Quality-Database/Compare-cameras/ (appareil1) 247|0 (appareil2) 188|0 (appareil3) 240|0 (onglet) 0 (brand) Canon (brand2) Canon (brand3) Panasonic

The G10 indeed comes out about 2/3 stop more sensitive than the 1D3; but the LX3 is tested at LESS sensitivity. It makes no sense. And it is not a manufacturer consistent design choice; the Panasonic FZ28 has pretty much exactly the same ISO calibration as the G10.

The combination of my own tests, together with the lack of consistency of DxO's LX3 ISO test with respect to pretty much any other digicam they have tested, leads me to disbelieve their results for the LX3.

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