Samples photos taken with the Sony Alpha DSLR-A700
The A700 handles detail degradation very well as you bump up the sensor gain. There's practically no visible noise increase until ISO 1600, where the details begin to become fuzzy, though at ISO 3200 it's more obvious.
This animated GIF simulates the burst speed of the A700. (As it's in GIF format, it in no way represents the image quality, and it runs at about five frames per second, slightly faster than the A700's tested 4.8fps.) To start the loop again, hit Shift-Refresh in your browser.
In general, the amount of noise you'll see at high ISO speeds varies widely depending upon exposure, focus and focus area. For instance, this relatively bright exposure, shot at ISO 2000 (1/40 sec, f/4.5) displays absolutely no noise in the background fabric and a surprisingly saturated (albeit inaccurate) red for Hellboy's face.
This ISO 2000 is from the same scene as the previous slide was shot about 1.3 stops darker (1/40 sec, f/7.1), and you can see a little noise and smearing on the background fabric, as well as color variation across the flat gray surface. Though the colors are still quite saturated, the noise is much more visible throughout the image.
Sony significantly enhanced its DRO technology, which applies image adjustment curves to expand the tonal range, making it a bit more useful. Now there's an Advanced DRO option that analyzes 1,200 segments in the frame for theoretically better results. In addition, there's a DRO bracketing drive mode, and you can set the strength of the adjustments. You can produce some fairly subtle results, which I like, and because the bracket mode doesn't actually shoot three photos, it's more consistent (and faster) to use than typical exposure bracketing.
By its maximum sensitivity of ISO 6400, the A700's photos develop color noise, though they hold detail reasonably well. I wouldn't crop too closely for these shots, but they hold up decently for printing--up to 12x17, if you don't mind the speckles. (This image was shot at 1/80 sec, f/4.5, ISO 6400.)