Photo from Canon A570 IS page

Sensor type: 1/2.5" CCD Pixels: 7.1 Mp, 4:3 Pixel pitch: 1.87 μm/pixel	2304 pixels 4.29 mm = 537 px/mm
3072 pixels 5.76 mm = 533 px/mm

Remote capture:  No
Remote focus control: n/a
Lens compatible with eyepieces: Yes
Raw mode: No (yes with CHDK)
Filter mount: Yes, 52 mm, with LA-DC52C adapter

No computer control ('remote capture')

The A570 does not support control of the camera from a computer via USB. When mounted on an optical device, eg., a microscope, photos need to be focused and captured using the camera.

Photographing what human eyes can see through optical instruments

The entrance pupil of this camera is similar to the human eye, so it's suitable for taking photos through optical instruments such as a microscope or binoculars. Here's a page with ideas for afocal adapters to use this camera with various optics.

When in manual focus mode, this camera displays an expanded, actual pixel view of the center of the image, as an inset into the normal view displayed on the camera's LCD. This greatly assists focusing.

JPEG compression: Fine vs Superfine

Based on MTF analysis and test photos, I'd say 'superfine' compression is about the same as 'fine' on the A570 and therefore not worth the extra file size. I presume this improvement over the Canon A75, an earlier model, is due to better JPEG compression. On more recent cameras, Canon has dropped the 'superfine' setting.

Spatial frequency response: MTF

The A570 lens is diffraction-limited at ƒ/6.0, which is inside its smallest aperture of ƒ/8. This means that photos taken with apertures smaller than ƒ/6.0 with this camera will have sharpness limited by diffraction (a 'pinhole' effect), even if the optics were perfect. Below are MTF analyses at ƒ/5.5 and ƒ/8.0 at full zoom (23.2 mm), using a slanted edge with contrast low enough to not trigger the camera's in-built image sharpening mechanisms (at least that's the presumption; at higher contrasts, there is an obvious overshoot in the edge profile created by sharpening). The target was a test pattern on an LCD display, photographed with the camera tilted 5 degrees. The JPEG compression was set at 'superfine'.

Canon A570, ƒ/5.5 at full zoom (23.2 mm), 'superfine' JPEG compression

The pale, dashed brown line marks the limit set by diffraction by the lens aperture and the pixel spacing. At ƒ/5.5, above, the MTF curve is well below the diffraction limit, and is therefore limited by the lens optics. However, below, at ƒ/8.0, the MTF is pretty much limited by diffraction -- but note that the MTF50 value is still comparable with that at ƒ/5.5. So the resolution (sharpness) of this camera is not as good as it could be given the high pixel count, but it still could be better than other cameras with fewer pixels.

Canon A570, ƒ/8.0 at full zoom (23.2 mm), 'superfine' JPEG compression

For more information about MTF and resolution, see Measuring resolution.

Focal length versus Angle of view

The camera was set 100cm from a perpendicular tape measure (measured from the back of the camera). Photos were taken at various focal lengths, and then the angle of view was calculated. It's possible the angle of view is affected by the focus distance.