Model Design / Appearance (7.5)
The Optio S5z is the high end of the Optio S series. The series is a moderately attractive group of cameras, and clearly Pentax has put in a fair amount of effort to make the Optio S5z a bit more attractive, or at least more sumptuous than the others. The proportions are very nicely balanced: the lens dominates the front, but that's appropriate, and it doesn't overwhelm. The contours and rounded details soften the camera's rectangular silhouette in subtle, pleasant ways. The top of the camera is rounded, from front to back, a little like a loaf of bread. The buttons are small, but they're identified with readable icons or labels.
The circular texture on the front of the camera is very striking, producing highlights that radiate from the lens, but it's hard to keep clean. Fingerprints show up on it as prominent smudges.
Size / Portability (6.5)
The Optio S5z is a mere 3.3 x 2.2 x 0.8 inches and 4.2 ounces, smaller than a typical computer mouse, and easy to carry in a pocket. When it's turned off, the surfaces are relatively smooth, and the lens retracts all the way into the camera, where it is well-protected.
The Optio S5z's metal shell offers good protection against pressure and torsion that the camera is likely to sustain, but the exterior casing is not sealed well against dust. The lens cover’s two halves butt up against each other, rather than overlap, and there is no seal around the edge of the opening they cover.
The sliding port covers for the data and power jacks don't seal tightly, and the seams between the front and back of the camera aren't tight. It's wise to protect any camera from dust, but the Optio S5z has a few prominent paths which dust might follow into the camera's internal components. If you want a camera to carry in a pocket or backpack, you probably ought to get one that's more dust-resistant than the Optio S5z.
Handling Ability (6.0)
The Optio S5z is a small pocket-sized camera. While small size is an advantage when you're carrying or storing a camera, it can be a problem when you use one. Both size and weight can be useful means of stability. Cameras as small as the Optio S5z, with limited surface area, are forced to scale their controls to the size of the frame and will generally be somewhat tedious to handle. Pentax designers compensate partially with intelligent placement of controls and by leaving space on the camera for grip.

The most natural way to hold the camera is to squeeze it between the right thumb, which lands on the excellently textured spot on the back of the camera, and the first two right-hand fingers. However, other than the finely grooved surface there is no texture on the front of the camera, making it difficult to get a solid grasp on the frame. The thumb and index finger of the left hand can grip the camera from the top and bottom without hitting any controls or covering any indicator lights. As I hold the Optio S5z, my right middle finger sometimes blocks the red window in the upper left corner of the front of the camera. Fortunately, the designers anticipated that – the window is the remote control receiver, which is only useful when the camera is on a tripod, not when anyone is holding it.
Also, the slab-like shape of the Optio S5z gives it a relatively high center of gravity, while larger compact cameras are built low and spread out somewhat. While this may not affect handling much, it does make the camera far more likely to tip over if balanced on edge.
Control Button / Dial Positioning / Size (6.5)
The Optio S5z buttons are small and closer together than they should be. Following a trend in very small cameras, the designers of the Optio S5z made the camera’s essential controls fairly stiff—corresponding buttons on larger cameras respond to a lighter touch than these. It seems as though this is a response to users' frustration at accidentally activating controls. It's a reasonable solution with buttons that are essentially on/off switches, such as the Playback button, but it doesn't work well with the zoom rocker. Once you press that hard enough to get the lens moving, you have zoomed quite a bit. If you try to make a small adjustment, you'll overshoot your goal more often than not.
The shutter release is nicely formed and is far less stiff than the camera’s other controls. You don't have to press it far to activate focus, but it is easy to feel when it locks.
The Optio S5z’s power switch is a button; press it once, the camera turns on, press it again, the camera shuts down. The button is recessed and requires a determined push to operate, which should cut down on the chance that the camera will accidentally be turned on in a pocket or bag. Still, sliding or turning switches are a better option than a button for turning cameras on or off. Check out the Kodak EasyShare C360, which uses its large mode dial as the power control. It would be just about impossible to accidentally turn on the C360.
The Optio S5z's “Quick” button actuates two functions that are likely to be popular with users: in shooting mode, it sets the camera to full auto, and in Playback mode, it deletes images. It's an example of good judgment by the camera's designers – such a small camera really shouldn't have any extra buttons, but it's very useful to have direct access to frequently-used controls.
It's notable that the Optio S5z designers chose not to spread out the controls on this camera. The next step down in the Optio line, the S55, has the Playback and Trash buttons on top of the camera, above the LCD. That design left more room open on the back of the camera, and meant that the two controls could be spaced well apart. The same strategy on the Optio S5z wouldn't have worked – the camera is so small that the user's left index finger would have rested on them.
Overall, the Optio S5z controls are well-implemented, given the size constraints of the camera body. The buttons don't get smaller than a fairly workable minimum size and they control the functions that are most likely to require direct access.
Menu (7.0)
The menus on the Optio S5z are attractive and easy to read. They appear in large, white type, rimmed in black, and they're superimposed over the live image feed. The menu is subdivided into two tabs, one called “Rec. Mode” for shooting options, and one called “Set-up,” for interface options and utilities. Both are fairly long submenus – Rec. Mode has 18 options and Set-up has 15, so it takes a fair amount of scrolling to reach every option. Fortunately, the most often used submenu items are placed toward the top of the list.
On the Rec. Mode list, they start with “Recorded Pixels,” or file size; Quality Level, which sets the amount of JPEG compression; White Balance; Metering Sensitivity, which sets the metering pattern; ISO; EV compensation; Movie mode, which switches the movie mode between normal and time-lapse movies; Digital Zoom; Aux AF Light; Instant Review, which sets how long images are displayed after they're shot; Memory, which controls whether custom settings are saved when the camera is turned off; Fn setting, which allows the user to customize the functions of the four-way controller; Quick Button, which sets the function of the Quick Button; Sharpness; Saturation; and Contrast.
The Set-up list begins with Format, which wipes all data from the SD memory card; Sound, which offers a range of noises for the camera to make as various functions are accomplished; Date Adjust; World Time, which sets the time zone in which the camera is being used; Language; USB connection, for choosing between connecting the camera to a computer or to a printer; Video out, for setting the analog video out signal to PAL or NTSC; Brightness, for adjusting the LCD display, not the images the camera saves; Quick Zoom, for setting a Playback magnification setting that the camera will jump to when the zoom button is hit once; Quick Delete, to directly erase images; Sleep timeout, to set the amount of time the camera will sit unused before it goes into a power-saving mode; Auto Power Off, to set the amount of time before the camera shuts off entirely, if left unattended; Guide Display, which controls what information is displayed on the LCD in shooting and Playback modes; and Reset, which returns the camera to factory settings.

In addition to the standard text menus, the Optio S5z interface includes a separate, icon-based Mode menu, which accesses image presets, movie mode, and automatic mode.
In Playback, the Mode button brings up an icon-based menu of image editing controls for both still images and video. The still image editing tools allow sizing and cropping, plus colorizing and brightness adjustment. The menu also includes direct printing controls, and the option to record voice memos attached to images. On the video side, editing options include splitting clips and cutting sections.
Ease of Use (6.5)
The Optio S5z allows easy control of its various automatic settings and functions, and also contains useful shortcuts to access frequently-used modes. The camera's layout makes the most of the limited space available, so holding the camera and operating it is as easy as it could be on such a small model.
However, the flaws inherent in the camera’s design will still be prohibitive for a number of users. The camera’s buttons are small and grouped close together. Camera size is all about tradeoffs. Optio S5z users get portability, but they give up a considerable amount of smooth handling.