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End of the line for Canon's midsize sensor?

It ain't over till it's over, but it looks like Canon's intermediate-size APS-H sensor line, found in 1D Mark III SLRs used by photojournalists, may be at the end of its life span.

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Stephen Shankland
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It looks like Canon's intermediate-size APS-H sensor line, found in the 1D Mark III SLRs used by photojournalists, may be at the end of its life span.

A silicon chip wafer from Canon can fit only 20 full-frame sensors, and there's lots of wasted real estate. Canon

The sensor is larger than the APS-C sensors used in mainstream Canon SLRs such as the EOS-40D or the new Canon EOS Rebel XSi, but it's smaller than those in a 1Ds Mark III or 5D, which is the size of a full frame of 35mm film. With Nikon now selling its first full-frame model, the D3, and Sony planning to launch its own full-frame competitor by the end of 2008, I have been curious if those developments meant momentum is shifting toward full-frame. Accordingly, at the Photo Marketing Association trade show, I asked Chuck Westfall, technical adviser for Canon USA's professional products marketing division, about the future of APS-H.

He didn't say anything definite (click here for the full Westfall Q&A), but it's hard to feel optimistic about the format's future. Westfall said the only advantage APS-H has over full-frame is price. And although that's significant, I can't help but notice that Nikon's full-frame D3 is a strong competitor to the 1D Mark III that largely matches its price.

"When we started it at the time, the idea was to compete against APS-C. In that respect it was successful...We've had a good, long run with APS-H," Westfall said. "Going forward, it remains to be seen whether it will continue to be a desirable format. We're not ready to say it's over."

With a rosier future for full-frame cameras, it's not clear to me that anyone will really miss APS-H if it goes extinct.

Chuck Westfall Canon

With Nikon showing that price doesn't need to be as much of an issue, the photojournalists who are the core market for the 1D Mark III could fare just fine with a full-frame model designed for their high-speed, low-light needs--the 1D Mark IV, perhaps. And for those photogs on the NFL sidelines who might like APS-H's slight telephoto effect, there could be an equivalent to the Nikon D3's DX crop mode that captures only central pixels from the sensor.

For background, there are some good reasons to employ different sensor sizes. Larger sensors of a given megapixel count permit larger pixels that do a better job distinguishing the signal of incoming light from electronic noise in the sensor, so photos have fewer speckles, colors remain more true, and cameras work better in low light. But large image sensors cost a lot more to build.

In the compact camera domain, there are multiple image-sensor sizes in use, but customers rarely know which because the lens is matched to it. In SLRs, though, where lenses are interchangeable, sensor size makes a difference. Lenses behave the same way as in the film era with cameras equipped with full-frame sensors, but the field of view is cropped more narrowly with APS-H and APS-C.

Because of this field-of-view crop factor, the field of view is 1.3 times narrower on an APS-H camera than a full-frame camera and 1.6 times narrower on an APS-C camera.

So for example, a 50mm lens on a full-frame 1Ds Mark III has the same field of view as a 38mm lens on an APS-H 1D Mark III and a 31mm lens on a Rebel XSi.

For telephoto shooting, smaller sensors are generally OK, in effect amplifying the ability to reach distant subjects. For wide-angle lenses, though, the arrival of SLRs with sensors smaller than full-frame initially posed problems. Now, though, camera makers have released new lenses with shorter focal lengths to cover the wider field of view.

Update 12:21 p.m. PST: Mike Baird, Ask.com's first vice president of engineering but now an avid camera buff, is one photographer who expects his 1D Mark III to be his last camera to have a sensor smaller than a full frame.

"I thoroughly expect the sub-35mm sensors to go away in the pro market," Baird said. "The APS-H 1D Mark III has replaced all of my APS-C cameras...I'd like the 1Ds Mark III, but I'm spending all my money on lenses."

Update at 8 a.m. PST on February 7: Westfall's title at Canon has changed and been duly noted.