Sony A550 Viewfinder

The Sony A550 features a digital SLR design, so the optical viewfinder offers a true, through-the-lens (TTL) display. A dioptric adjustment dial to the right of the eyepiece accommodates eyeglass wearers, letting them adjust the viewfinder optics between -2.5 to +1.0 diopters. The viewfinder eyepiece has a fairly typical eyepoint (specified at 19mm from the eyepiece, 15mm from the eyepiece frame with the dioptric adjustment set to -1 diopter), though the articulating LCD makes it difficult to get your eye close enough to see the entire viewfinder and status display all at once. Magnification is pretty low at only 0.80x for a 50mm lens and -1 diopter of dioptric correction, but an improvement over the A380's 0.74x magnification. Coverage is specified at 95%, typical for non-pro SLRs.

The Sony A550's viewfinder uses a pentamirror design. The advantage of a pentamirror is it's lighter and less expensive; however an all-glass pentaprism design delivers more light to the viewfinder eyepiece, thanks to its more efficient internal reflection. A solid pentaprism isn't compatible with Sony's tilting-mirror Quick AF Live View mechanism, though.

The Sony A550's fairly extensive information display features a series of focus target marks in the center of the view that highlight briefly when the AF system is activated. The focus dots found inside the AF targets on A230, A330 and A380 are no longer present. Markers are provided for 16:9 shooting area, as well as spot metering area. They only appear when the associated feature is enabled. All markers are LCD overlays (as opposed to being etched on the focusing screen), so when the camera is shut off, none of them appear.

Camera information appears beneath the image area in a small strip, and reports the camera's major settings, such as shutter speed, aperture, flash mode, EV compensation, etc. To the far right side of the strip is the SteadyShot (anti-shake) scale, indicating the degree of stabilization whenever anti-shake mode is activated. The information readout in the viewfinder activates whenever you half-press the Shutter button, and remains active for a few seconds afterward.

A pair of horizontal infrared sensors just below the viewfinder detect your eye as it approaches the viewfinder, and deactivates the LCD information display if you have the Auto Off w/ VF option enabled in the Custom menu. (Note: our camera picked-up the IR beam in the image at right. The beam is invisible to the naked eye.) You can also set these sensors to initiate autofocus whenever your eye is in range of the eyepiece (Eye-Start AF), which makes the A550's autofocus seem even more responsive.


Viewfinder Test Results

Good accuracy from the optical viewfinder, but Quick AF Live View mode was less accurate. Manual Focus Check mode was very accurate.

Optical Viewfinder
LCD (Quick AF Live View)
LCD (Manual Focus Check Live View)

The Sony Alpha 550's optical viewfinder showed about 95 percent coverage accuracy with our Sigma 70mm f/2.8 prime lens, matching Sony's specification. The image does however appear slightly tilted and shifted relative to the imaging sensor, which we're unfortunately seeing more and more frequently in consumer SLRs these days. The amount of tilt and shift on the Sony A550's finder isn't as bad as many we've seen, though.

Quick AF Live View mode had slightly less coverage at about 92%, but was also tilted and shifted very slightly. We're used to seeing close to 100% coverage from cameras' LCDs in Live View mode, but Sony's approach of using a secondary image sensor for Quick AF Live View rather than the main imager means that lower coverage and minor misalignments like this can occur. (The upside, of course, is much faster shutter response than most Live-View SLRs that use the main image sensor for the Live View viewfinder display.)

Coverage in Manual Focus Check Live View mode, which displays an image derived from the main imaging sensor, is 100%, however we found this mode to be somewhat limiting in usefulness, as it only displays for a few seconds then shuts off. It really is only meant for a quick focus check.


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