Analog / Digital Converters

[scottbergerphoto]

All of the comparisons about the 20D and Rebel XT and 20D and 1DMII, got me thinking about how one thing I never see compared is the quality of the A/D Converter in the respective cameras. My understanding is the A/D Converter is one of the most important factors in determining image quality for cameras with the same sensors. Most P&S cameras have the same image sensor made by SONY, but have widely varying image quality. DPP says the reason is the A/D Converter.
Any thoughts?
Scott

[Jon]

That may be so in the P&S world, at least for same-size sensors, but for the DRXT, 20D, and 1D Mk II, they're all using different sensors (different sizes and/or resolutions) with essentially the same DiGiC II DAC, so we're seeing sensor differences. Even with the P/S, it's important to only compare cameras that are positively using the same off-the-shelf sensor, not requested variants on the same. And I still wouldn't want to rule out the sensor packaging (heat?), lens quality, metering algorithms, or the stability of the power supply. If someone blew the selections on all of those, (not likely, I'll admit) a good DAC would have to be very good to pull it out. For that matter, don't I recall Sony touting that they use "Emerald" in addition to R, G, and B on their 8 MP prosumer model?

[robertwgross]

A/D converters come in different depths, or a different number of steps. In general, the more steps, the finer it can resolve continuous tones. However, in just about everything like this, there are non-linearities that have to be fudged out somehow, things just a little more complicated than Gamma.

In a quality product, the non-linearities are well understood, and the processor can fudge them out. In a cheap product, the non-linearities are still rattling around in the image file, and good eyes can find them.

---Bob Gross---