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Tuesday, November 2, 2010

Camera Tech You Need To Know About

These days, a lot of innovation in photography is starting out in lower-end cameras. Some of these features are going to change the way you work as a pro.

This Article Features Photo Zoom

The new pellicle mirror system in the Sony SLT-A55 is fundamentally different from previous pellicle designs.

Pro DSLRs provide a lot of vital features, many of which have been around since film days: quick, accurate autofocusing; multi-area metering (plus centerweighted and spot, when desired); rapid shooting rates; rugged, well-sealed bodies; excellent image quality, even at higher ISO settings; 100% optical viewfinders; and 3-inch, 920,000-dot LCD monitors, sensor dust removers, handy live-view operation and more.

But there are features that haven’t yet come to the pro DSLR—or that have come only recently—of which you should be aware. In this article, we look at some technologies that have been filtering their way into consumer-level cameras, but that we think will—or should—soon make their way into higher-end pro-level DSLRs. At a glance, you might dismiss some of these features as gimmicks, but look closer, and you’ll start to see serious potential.

EVFs and mirrorless designs are the wave of the future.
Pellicle Mirrors
SLRs are wonderful, showing you the image formed by the lens, regardless of focal length or shooting distance, and enabling you to see when the image is sharply focused. But along with these benefits come some drawbacks. It takes time—not a lot, but measurable—for the mirror to flip up out of the light path and then back down into viewing position once the exposure has been made. During this “blackout” period, you can’t see anything in the finder, and the camera’s phase-detection AF system can’t function—so the camera must focus, then shoot, then reacquire the subject and focus, then shoot. The mirror’s movement causes vibrations that can reduce image sharpness. And the mirror box, focusing screen and pentaprism add bulk and complexity (and cost) to the camera body.

By using a semitransparent pellicle mirror, SLR designers can provide SLR viewing without having to move the mirror. This eliminates mirror vibration and mirror blackout, as well as the bulk and cost of a moving mirror assembly and associated mechanisms, and can speed up shooting as well. The main drawback is that the pellicle mirror doesn’t transmit all the light from the lens to the image plane, so exposure must be increased to compensate, and the viewfinder image is dimmer than with a conventional SLR.

Use of a pellicle mirror in an SLR isn’t new. Canon offered the Pellix back in 1965, with a fixed pellicle mirror and the selling point of no viewfinder blackout while shooting (as well as no mirror vibration, less weight and minus the cost of a moving mirror mechanism). Of course, that was a 35mm film camera, with no motordrive. In 1972, Canon introduced the pro F-1 High Speed Motor Drive Camera, with a fixed pellicle mirror that enabled a top shooting rate of 9 fps—you could blow through a 36-exposure roll of film in four seconds! That was followed by a model in 1984, which could do 14 fps. In 1989, Canon introduced the EOS RT with a fixed pellicle mirror that reduced shutter-release lag time to just 0.008 seconds—the first AF pellicle-mirror SLR.

Fast-forward to today: Sony’s new SLT-A55 and SLT-A33 are the first digital SLRs to employ pellicle mirrors. That is, they look like DSLRs, but they do away with the pellicle-mirror, dim-viewfinder problem (and pentaprism/pentamirror finder bulk) by employing an eye-level electronic viewfinder instead of an optical SLR finder. Because the mirror doesn’t have to move, the camera can focus and shoot simultaneously for super-quick operation; in Continuous Priority AE mode, the A55 can shoot its 16.2-megapixel images at 10 fps— pro-DSLR speed. Another advantage is that you have convenient eye-level viewing when shooting videos, something the moving-mirror DSLRs don’t provide.


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