Casio EX-S770

Reviewed January 2007

Image Quality

The Casio Exilim EX-S770 maintains Casio as a leader in the area of super-compact digital cameras that fold flat and which can fit comfortably into a pocket or purse.

As with a number of similar cameras, the EX-S770 is a camera that has no optical viewfinder, but which instead provides a large 2.8-inch LCD monitor for framing and reviewing shots. As with all similarly designed cameras, the EX-S770 requires the user to hold the camera out with arms raised while looking at the monitor to frame the shot, a stance that is intrinsically less stable that holding the camera at eye-level with elbows tucked in.

While maintaining as low a sensitivity as possible to avoid noise and steadying the camera to avoid camera shake is the best course of action, that is not always possible.

The alternative is to either purposefully set the ISO sensitivity higher, or set the camera to Auto ISO, and allow it to boost the CCD sensitivity as required. Set to Auto, and without using the flash, the EX-S770 adjusts the CCD sensitivity between 50 and 200 ISO. While when the flash is used, the camera only boosts sensitivity up to 100 ISO.

At 200 ISO, the camera enters a range where noise becomes noticeable in the image when it is seen at 100% on a monitor. At 400 ISO, the "grain" is coarser, and causes a loss of definition in the image. Still, if the image is printed out at no more than 4 x 6 inch (10 x 15 cm) the quality is acceptable.

The EX-S-770 also offers a "High Sensitivity" scene mode that pushes sensitivity to 800 ISO. At this level, however, noise is pervasive in the image, limiting its usefulness.

In a similar vein, another mode called Anti-Shake also increases sensitivity, thereby allowing a faster shutter speed to prevent camera shake, but increasing noise. This mode should not, however, be confused with optical or CCD stabilization systems that do not increase sensitivity, but instead physically counteract camera shake.

Given a well-lit subject, the EX-S770 produces good results. In large part this seems to be due to two critical elements of the camera. First, the multi-segment metering is quite adept at evaluating the overall frame, and takes into account both high and low lights. Moreover, it is not easily fooled, and even subjects that contain snow are rendered properly, with the snow looking white and not grey. The second is the auto white balance. It is, like the metering, very accurate, and even adapts to incandescent lighting quite well.

The 3X zoom lens of the EX-S770 has a focal length range that is equivalent to a 38 to 114 mm, which progresses through its range in 6 clearly defined steps corresponding to 38, 47, 55, 79, 94, and 114 mm. This focal length range, popular with 3X zoom compacts, is a compromise, trading a bit at the wide end to offer a bit longer telephoto. In other words, it is a focal length range that should be useable for most common shots.

At the wide angle end, the lens is generally distortion-free, but high contrast subjects can reveal a small chromatic aberration, while the remainder of the focal length range is free of any distortion or aberration.

Similarly, the image sharpness the lens yields appears to be quite reasonable, but when photos are inspected at 100% scale on a monitor, the compression appears to sacrifice some detail.

Three compression levels are available with the EX-S770: Fine (5:1); Normal (10:1); and Economy (15:1).

Although the Fine setting applies a level compression that generally avoids artefacts, in this case it still appears to be a bit strong with some subjects, and will sometimes cause a slight smudging of the edges of objects in an image. Still, with most subjects, the Fine level is quite good and yields an image quality that is on par with comparable compact cameras.

When used with flash, the EX-S770 yields brighter images than its predecessors. Clearly, Casio has refined the Flash Assist system which is set to On by default. The system works by detecting when the flash's output was insufficient to light the farthest parts of a subject, and processes the image to increase its brightness prior to saving it. While when it was first introduced the Flash Assist system tended to make noise more visible, that is no longer the case. And, while it will not brighten a subject that is clearly out of range for the tiny flash, it is generally effective.