Sony A330 Viewfinder
The Sony A330 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 -3.0 to +1.0 diopters. The viewfinder eyepiece has a fairly typical eyepoint (specified at 19.7mm from the eyepiece, 14.1mm from the eyepiece frame with the dioptric adjustment set to -1 diopter). Magnification is pretty low at only 0.74x for a 50mm lens and -1 diopter of dioptric correction. This is due to the room needed for the Live View sensor, and results in a noticeably smaller than average view through the optical viewfinder. Coverage is specified at 95%, typical for non-pro SLRs.
Like the Sony A300, the A330'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 Live View mechanism, though.
The Sony A330's information display features a series of focus target marks in the center of the view that highlight briefly when the AF system is activated. Note that the line-type AF-Point displays from previous generations of Sony SLRs have been replaced by boxes, however only the center AF sensor is a cross-type. Markers are provided for 16:9 shooting area, as well as the general AF area.
Camera information appears beneath the image area in a small strip, and reports all of the major camera settings, such as shutter speed, aperture, flash mode, EV compensation, etc. To the far right side of the strip is the Super 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 A330's autofocus seem even more responsive.
Viewfinder Test Results
Coverage
Good accuracy from the optical viewfinder, but the LCD was less accurate.
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70mm, Optical
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70mm, LCD (Live View)
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The Sony Alpha 330's optical viewfinder showed about 96 percent coverage accuracy with our Sigma 70mm f/2.8 prime standard test lens. This is quite good for an entry-level digital SLR, beating Sony's specification of 95% by just a bit. The image does however appear tilted (about 0.7 degrees) and shifted relative to the imaging sensor, which we're unfortunately seeing more and more frequently in consumer SLRs these days. Live View mode had slightly less coverage at about 93%, but was also tilted and shifted somewhat, although the tilt wasn't quite as bad as in the optical viewfinder. 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 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.)
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