Although it lacks the manual exposure adjustments enthusiasts insist on, the Optio provides plenty of controls for those who want to participate more actively in the picture-taking process. For example, with the 35.6mm-to-107mm zoom lens (35mm-camera equivalent) you can choose 7-point autofocus, center spot focus, or select your own focus area from any of 49 positions. There's even a manual focus option to allow better control over sharpness and depth of field. Close-up modes take you down to 7 inches in normal macro mode and as close as 2 inches in supermacro mode. The flash was usable in close-up mode down to 8 inches and reached out to 11.5 feet at normal distances. You can set sensitivity to auto or manually select between ISO 80 and ISO 400. Shutter speeds range from 4 seconds to 1/2,000 second, and sound movies can be grabbed at a disappointing 320x240 pixels and 15fps.
Unfortunately, the Pentax Optio S5i turned in a mixed performance overall. Shutter lag was outstanding at 0.5 second under high-contrast lighting and 0.8 second under more challenging low-contrast lighting conditions, despite the lack of a focus-assist lamp. The camera took a moderate 4.2 seconds to awaken from its slumber after power-on, but delays between shots seemed interminably long: 4.8 seconds without the flash and a hair more than 7 seconds with the flash active. At full resolution, this camera's burst mode hardly merits the name. It will obligingly snap off pictures as long as the shutter release is pressed but waits 4 seconds between shots, taking 10 pictures in 40 seconds. Reducing resolution in steps picked up the pace, until it snapped 1fps at 640x480 resolution.
Pentax supplies a dock for charging the Optio's battery, which proved game for 320 shots (half with flash) during a workout that included zooming, card formatting, and other power-hungry tasks. The LCD performed well in all but the brightest light and wasn't overly susceptible to ghosting, but the optical viewfinder's perspective is a little on the small side and won't please those who like to see details as they compose their pictures.
Image quality was good but not outstanding. It delivered full, saturated colors under ordinary circumstances, although colors looked a bit muted outdoors on the overcast day when part of our tests were conducted. The S5i rendered skin tones well but had a minor tendency to wash out lighter tones and introduced some purple fringing around backlit subjects. Red-eye control seemed good, and noise at ISO 400 was noticeable but not overpowering.