My coworker Lori Grunin already covered, but as somebody who's in the market for a new SLR, I thought I'd weigh in with some thoughts of my own. I'm glad Canon is investing where perhaps it counts most: the sensor. If the reviews look good, this will be the first time I've really been tempted to upgrade from my well-used Canon Rebel XT.
When it ships in October, the 50D will sport a 15.1 megapixel sensor, up from 10.1 megapixels in the current 40D. The increase in megapixels is nice for the poster-print and microstock-sales crowds, but what's most notable is the increase of the top ISO from 3,200 to 12,800.
That means Canon has done some serious work to cut down on the noise levels inside the sensor, which bodes well for image quality not just at the new extremes but also at more ordinary sensitivity settings. ISO 3,200, for example, is now part of the ordinary range, not the extended range that must be manually enabled before it's available. Canon hit some sweet spots in sensor design, for example with its earlier 20D and the full-frame 5D, and the 50D holds the potential of being another model that balances megapixels with low noise and accurate color.
Canon attributes the advance to "newly designed gapless microlenses over each pixel to reduce noise." Microlenses gather light for the light-sensitive part of the image sensor, compensating for surface area occupied by other electronics. Gapless microlenses presumably stretch across the entire pixel width. Perhaps this technology will also help out whatever model will succeed Canon's 5D, my other obvious upgrade path but one that likely would require spending twice the price for the camera body and that would require me to shell out another few hundred dollars for a new wide-angle lens to support the full-frame sensor size.
Fending off Nikon
Higher sensitivity is important for Canon. It's been losing market share to Nikon, which has pushed high sensitivity as an advantage, though with lower megapixel counts. The full-frame sensors on Nikon's D3 and D700 can reach ISO 25,600, though reaching that level was made easier through a sensor design that emphasizes a smaller number of larger pixels.
The 50D has some other features that sound promising, including a higher-resolution 3-inch display, the new Digic 4 image-processing chip, a more dust-repellant sensor coating to avoid image-degrading speckles, HDMI (High-Definition Multimedia Interface) output for nicer output on high-definition TVs, and the higher-speed UDMA CompactFlash standard. It's also got a built-in database of lens characteristics that can help correct for vignetting, the darker corners that some lenses produce.
Photography buffs who know their way around a $1,400 SLR may sneer at dummy modes for portrait, macro, and sports shots, or the new Creative Auto Mode (CA) that offers photographers English-language options such as "blur the background" and sets the camera accordingly. I think that's shortsighted, though: even if you know how to best balance depth of field and shutter speed, perhaps somebody else in your family doesn't. My complaint with the automatic settings is that at least in my camera, they only permit shooting in JPEG. I prefer raw, and even if somebody else is shooting, I'm usually the one who processes the images. (Update Oct. 9: The 50D can shoot raw even in the automatic modes. Huzzah! Another big advantage over my Rebel XT.)
Two areas concern me, though.
First is live view. Canon claims its latest attempt is better, but I remain skeptical it'll match the expectations of those with point-and-shoot cameras who've grown accustomed to framing the shots through the display rather than the viewfinder. Focusing sluggishness and pauses while a mirror flips up and down have seriously degraded live view on most SLRs.
It doesn't bother me much, since I'm happy with the viewfinder. But I have friends who demand it, and I do see its utility for taking shots while holding the camera overhead or low to the ground. Live view also is nice when you want to talk to photographic subjects rather than hide your face behind the camera.
A more personal concern is weather sealing. I'm careful with my cameras, but I shoot sometimes in light rain, San Francisco mizzle, or waterfall spray. And on hiking and camping trips, dust is a serious concern. Full weather sealing is expensive, but it's an area where Canon competitors have been leading the charge, and it's important to me.
Finally, a modern Canon ultrazoom
Another smart Canon countermove to Nikon is the EF-S 18-200mm f/3.5-5.6 IS lens, costing $700 and also due in October.
With a zoom range that long, you can bet the lens will have some serious compromises in areas such as sharpness, vignetting, distortion that can bow parallel lines into a barrel shape, or the chromatic aberration that can leave colored fringes around object edges. But that won't matter much to the large fraction of SLR buyers who don't want the expense, hassle, and bulk of multiple lenses. Nikon's 18-200mm lens has been its best-selling ever, despite a similarly steep price tag and highly limited initial availability.
It's probably not the lens for me, but I know several people waiting for something of its ilk, so Canon is smart to offer it. I'd probably rather put $700 toward a big telephoto lens if I were in a lavish spending mood.
Even then, I confess this all-purpose model is tempting for the next seven-day backpacking trip or Argentina tour when lugging lots of lenses is a huge effort. I have no such ambivalence with the 50D, though. It's aimed squarely at photography enthusiasts such as myself, and you can bet I'll be poring over the reviews to see if the 50D performance matches the promise of the press release.