The Optio 550 is equipped with a 5X Pentax power zoom 7.8-39mm (equivalent to 37.5 - 187.5mm in 35mm format) f/2.8 - f/4.6, 9 elements in 7 groups (2 dual-sided aspherical elements.) When powered down the lens automatically retracts into the camera and is protected by a builtin lens cap.

Featuring a high speed Hybrid AF system using a TTL contrast detection system combined with an exo-passive sensor. Selectable Wide and Spot AF. User can manually select one of five AF areas. Manual and infinity focus modes.

Autofocus Range:

Normal: 1.97 ft. (0.6m) to infinity.
Macro: 5.9 in. (0.15m) to 2.13 ft. (0.65m).
Super Macro: 0.79 in. (0.02m) to 2.13 ft. (0.65m)
Manual focus: 0.79 in. (0.02m) to infinity.

The optical viewfinder has about 85% coverage and a dioptric adjustment. There are no framing or focus area indicators in the viewfinder. The two LEDs indicate auto focus and flash status.

The built-in flash has modes for auto flash, fill-flash in low lighting and backlight condition, flash-on and flash-off and "Red-eye" reduction function which employs a single discharge. The flash working range in wide angle is approx. 1.31 ft. - 17.1 ft. (0.4m - 5.2m) (7.8mm at ISO Auto); in telephoto is approx. 0.5 ft. - 10.5 ft. (0.15m - 3.2m) (39mm at ISO Auto)

There are dedicated buttons for the Flash mode (Protect/Unprotect in play mode), Drive mode (DPOF in play) and Focus mode (image Delete in play.) The zoom controls function as the image Index and Magnify buttons in play mode. The button above and to the left of the 4-way is the Play mode button, press it to review images and tap the shutter release to quickly go back to record mode again. The MENU button calls up or dismisses the onscreen menu system. The DISPLAY button turns the color LCD on/off and controls the data overlayed on it as well as the histogram and grid display modes.

The 4-way selector switch is for navigating menu options, press the OK button in the center to accept selections. Press "Right" and "Left" to change the exposure compensation. The user can assign Functions to the Up, Down, Left and Right buttons when used in conjunction with the Menu/Function button. You can assign any one of these functions to each of the 4-way's buttons: Image size, image quality, white balance, focusing area, AE metering, ISO speed, digital zoom, instant review, sharpness, saturation or contrast.

On top you'll find the power On/Off button and the shutter release in the center of the Mode Dial. The Mode Dial gives you quick access to: Metered Manual, Shutter-priority, Aperture-priority, Program AE, Picture (Scene), Movie, Panorama Assist, 3D image, Digital Filter, User and Sound Recording modes.

Images and movie clips are stored on either Secure Digital (SD) or MultiMedia Card (MMC) memory cards, Pentax provides a 16MB size SD card with the camera.

There is a miniature connector on the side to facilitate both the USB 1.1 data cable and the Audio / Video cable for connection to a TV set.

Below that is the DC IN port for an optional AC power supply or external battery pack.

The Optio 550/450 is powered by a proprietary Pentax D-LI7 lithium-ion 3.7v 1800mAh rechargeable battery pack. It is charged out of the camera with the supplied D-BC7 compact AC charger unit. Time required for a full charge is approx. 180 minutes maximum.

Pentax claims a battery life of up to 400 shots per charge (50% with flash, LCD monitor ON). Continuous playback time is 210 minutes.