23. Image Quality, Continued

Shot in aperture priority mode, aperture f/8, focal length 18mm.

Shot in aperture priority mode, aperture f/8, focal length 55mm.

100% detail of an 18mm f/3.5 shot, center of image.

100% detail of an 18mm f/3.5 shot, upper part of image.

100% detail of an 18mm f/11 shot, center of image.

100% detail of an 18mm f/11 shot, upper part of image.

100% detail of a 55mm f/5.6 shot, center of image.

100% detail of a 55mm f/5.6 shot, corner of image.

100% detail of a 55mm f/11 shot, center of image.

100% detail of a 55mm f/11 shot, corner of image.

Digital noise, as with many current digital SLRs, was very low at normal sensitivity settings (ISO 200 or ISO 400). Logically, it increased at higher sensitivities, but remained within reason up to ISO 1600. Using ISO 3200 on the Pentax istDL should be considered an option only for "impossible" shots, or to get a specific effect. Note that the graininess of an image depends heavily on the type of subject being photographed and on the exposure level; more noise will be visible in an underexposed image because it will generally be necessary to make extensive corrections to get a picture that's enjoyable to look at. In fact it's a little like using a sensitivity setting that's two or three times as high as the one you selected. So don't be surprised at the graininess.