Exposure Modes
Both the Sigma DP1 and the Canon G9 offer full automatic modes for point-and-shoot use. The DP1 limits its choices of ISO to 100 and 200 in auto mode – it's a severe limitation, but we found the color performance at 400 and 800 bad enough that we can understand the decision. Canon's G9 doesn't have that limitation. In other respects, the full auto modes are pretty unremarkable – in flat lighting and typical scenes, both do fine. The cameras also offer aperture, shutter and program priority modes, with the typical sorts of controls to bias exposure up or down. Both also offer manual modes, which are a little clumsy to use, given that the same set of buttons are used to control both aperture and shutter. The user has to use a different button to toggle from one parameter to the other. Both cameras show readouts of aperture and shutter speed, as well as deviation from the metered exposure.

The Canon G9 offers a live histogram, but the Sigma DP1 does not. That's a big advantage for the G9. The DP1 has a playback histogram, but of course, that's much slower to use.

The Sigma DP1's aperture range runs from f/4 to f/11, while the Canon G9's runs from f/2.8 to f/10. We found that a limitation when we shot the two cameras with studio flash, and couldn't dial down our lights low enough for a proper exposure with the G9. Clearly, that won't be a common problem, but it points out another limitation of the G9's small sensor – to accommodate it, Canon had to put a very short focal length lens on the camera, one so small that an f/11 aperture would be such a tiny hole that diffraction would degrade the image.