Sony A900 Viewfinder

Sony A900 Viewfinder (It's big, bright and accurate)

The Sony A900 is of course, an SLR, so the optical viewfinder offers a true, through-the-lens display. A dioptric adjustment dial accommodates eyeglass wearers, letting them adjust the viewfinder optics between -3.0 and +1.0 diopters. Specified at 20mm from the eyepiece, the eyepoint is good, but not quite as high as those of some other cameras, so eyeglass-wearer Dave found he had to press the lenses of his glasses pretty firmly against the A900's eyecup in order to see the full frame area.

If you're accustomed to shooting with sub-frame SLRs, the first thing you'll notice when looking into the Sony A900's viewfinder is how huge it is. When we first shot with it, one of the Sony staff in attendance joked that we'd need to hold onto the edges of the viewfinder bezel, to keep from falling into it: He wasn't far wrong. Viewfinder specifications commonly include things like eyepoint height and magnification ratio, but don't address how much of your apparent field of view the viewfinder image covers. If they did, the A900 would come out somewhere very high on the list. In practice, a much larger viewfinder like this does a lot to connect you with your subjects: You have much more of a sense of just looking at the subjects, rather than peering down a tunnel at them.

In terms of specs, the Sony A900's viewfinder has an optical magnification of 0.74x when using it with a 50mm lens focused at infinity and the dioptric adjustment set to -1 diopter. This is the same magnification as the A350's viewfinder, a bit more than that of the Nikon D700 (0.72x), a bit less than that of the Canon EOS-1Ds Mark III (0.76x). What the viewfinder magnification factor means in practice is that objects seen through the Sony A900's viewfinder when using a 50mm lens will be about 74% as large as they'd appear to your unaided eye; with a 70mm lens, they'd appear just slightly larger than normal size. The benefit of having a high magnification number is that it makes it easier to shoot with both eyes open, as the view through the viewfinder will be close to what your other eye is seeing, unaided. Having both eyes open when shooting greatly improves your situational awareness, making it much easier to acquire and track quickly moving objects. At least for lenses in the roughly 50 - 90 mm focal length range, the Sony A900 makes two-eyed shooting relatively easy.

Besides the huge view it gives you, the Sony A900's viewfinder also sports two other desirable characteristics. First, the 100% internal reflection of its true pentaprism optical design makes for a very bright image. Secondly, the A900's viewfinder offers true 100% frame coverage, making it easy to frame subjects very precisely. (Our lab measurement put the Sony A900's viewfinder accuracy at 99% on our test sample, within the margin of testing error of the claimed 100%.)


Sony A900 Viewfinder Information Display

The illustration above shows the information that's displayed in the Sony A900's optical viewfinder. There are the usual autofocus area markers, but also marks that delineate the 16:9 aspect ratio shooting area and the corners of the APS-C shooting area, for when you're running the camera in that mode, when using a sub-frame lens.

Along the bottom of the display are the usual indicators for shutter speed, aperture, exposure compensation and shots remaining in continuous mode. There's an unusual number of indicators associated with flash operation, thanks to the sophistication of Sony's flash offerings. There's the usual flash exposure compensation and flash-charging indicators, but also icons showing wireless flash (WL) and high-speed sync (H) operation. Since the Sony A900 has no internal flash, all flash functions require the use of an external flash, with a number of Sony models to choose from. To use the wireless flash triggering and control option, you need to have one of the top-end HVL-58AM models mounted on the camera to control the remote units, but all currently-manufactured Sony flash units can work as wireless remotes. All current Sony flash units are also capable of high-speed (also called "FP") synchronization, allowing flash exposures at any shutter speed the camera is capable of.

There's one additional indicator in the Sony A900's viewfinder that we particularly like: In the lower right-hand corner, there's what amounts to a little bar graph that's active whenever the SteadyShot image stabilization is in use. This shows how much camera shake the SteadyShot system is currently seeing. By waiting for the fewest bars to be displayed, you can pick a moment when shake is at its minimum, giving the SteadyShot system the best chance at completely compensating for it. This strikes us as quite handy, and is a feature we wish were available with lens-based IS systems. We'd wager that intelligent use of this display could add a good stop or so to minimum shooting speed, and could help the effective performance of the Sony A900's IS system.

User-Interchangeable Focusing Screens

While some previous Sony DSLR models had interchangeable focusing screens, this has always in the past been an option that could only be performed by a Sony service center. The reason for this was that the camera's exposure system would have to be adjusted for the focusing screen being swapped in. In the Sony A900 though, a Focusing Screen option on the Setup menu lets you specify which screen is in use, so the camera can adjust its exposure metering as needed.

There are three different focusing screens available for the Sony A900:

  • Type G - The default screen, a good trade-off between brightness and focus discrimination

  • Type M - A "Super Spherical Acute Matte" screen. This screen provides much sharper discrimination between in-focus and out-of-focus conditions, but at the cost of some brightness. It's only intended for use with lenses having maximum apertures of f/2.8 or greater.

  • Type L - This screen is the same brightness as the default Type G type, but provides a grid to help with horizontal/vertical alignment or rule-of-thirds composition.


Viewfinder Test Results

Very good accuracy from the optical viewfinder. The A900 does not support Live View on the LCD.

70mm, Optical

The Sony Alpha A900's optical viewfinder showed about 99 percent coverage accuracy with our Sigma 70mm f/2.8 prime lens. This is very good for a semi-pro digital SLR, just slightly below Sony's 100% specification. Sony chose not to offer a Live View mode on the A900, since Sony's Live View system would require a smaller, dimmer pentamirror design.


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