"Some of Canon’s competitors have chosen to use in-body image stabilization. The technique involves moving the image sensor in a controlled fashion, based on signals from movement detecting sensors in the camera body. The obvious advantage of this system is that users have some sort of stabilization available with almost any lens they connect to the body. Short focal length lenses require smaller sensor deflections; 24 or 28 mm lenses might need only 1 mm or so. Longer lenses necessitate much greater movement; 300 mm lenses would have to move the sensor about 5.5 mm (nearly 1/4”) to achieve the correction Canon gets with its IS system at the same focal length. This degree of sensor movement is beyond the range of current technology. Short and 'normal' focal length lenses need stabilization much less often than long lenses, so the lenses that need the most help get the least."
It seems to me that there are advantages and disadvantages to each alternative, but one thing that Canon's explanation sidesteps is whether the two implementation styles are necessarily mutually exclusive. The vast majority of photographers will never buy an image-stabilized 300mm or longer lens. For those who do, is it beyond Canon's technological prowess to make an in-camera IS that simply has to be turned off if and when you mount lenses that have their own IS? Plus, with five digital SLR bodies in its current lineup (30D, 5D, Rebel XTi, 1D Mk. II and 1Ds Mk. II), it wouldn't appear to be impossible for Canon to offer an in-body IS version of one of them, and let its customers choose.
Call me cynical, but I've been observing this business a long time, and how I translate Canon's explanation is more or less like this: "We make more money on in-lens stabilization, and since we're the biggest dog in the pack we're going to stick with that. Like it or lump it." (I hope the good folks at Canon will forgive my colorful mode of expression. But you get the point.)
Another objection I'd raise to Canon's explanation is that I think you need another clause behind the statement "Short and 'normal' focal length lenses need stabilization much less often than long lenses..." to wit: "...when you're shooting in good light." When you're shooting in low light, on the other hand, image stabilization can come in just as handy, just as often, with shorter lenses as when you're using long lenses in normal daylight. That's how I use the feature, anyway.
This was taken handheld by the light of two candles at 1/3rd sec. Don't try to tell me
that Anti-Shake doesn't help when using short lenses!
that Anti-Shake doesn't help when using short lenses!
It would be just as easy for the manufacturer of an in-body IS system to point out at that when you're shooting with 300mm, 400mm, and 600mm lenses, you'll most often be shooting from a tripod. In an event, I think all these are arguments as much as they are technical considerations.
1. More effective with longer lenses
2. You don't pay for it except with the lenses you need it for
3. You see the stabilization effects through the viewfinder
1. More expensive, especially if you want the feature in more than one lens
2. Not available with all lenses
1. Works with every lens you mount to the body, and may be the only option for many shorter and faster lenses
2. Less expensive, especially if you want the feature with more than one lens
1. Progressively less effective with longer and longer lenses
2. Progressively harder to implement with larger image sensors.
The only really decisive choice consideration would be that you'd choose the in-lens type if your overriding need is to hand-hold long lenses in normal light, and you'd choose the in-body type if your overriding need is to shoot hand-held with normal and short lenses in low light. Again, probably the best eventual capability would be to have it available in both the body and in certain long lenses, then just switch off the in-body IS when mounting an IS telephoto.
Cynical again: Canon or Nikon will do this just as soon as not having an in-body IS option starts looking like an obvious sales liability.
The Pentax Option
I did make a trip to my local photo emporium, Mike Crivello's, yesterday, to take a look at the new Pentax K10D. It's particularly unsatisfactory to simply handle DSLRs at a camera counter, because you just don't know enough about how it works to feel like you've learned much about it. Apart from being a nice-looking, ergonomically well-designed body that has approximately the build quality of the Canon 30D or Nikon D80, all I can really tell you about the Pentax is that the viewfinder is much better than those of entry-level cameras, but not as good as my K-M 7D, and the shutter noise is what I'd call moderate—not loud, not soft. See, that doesn't really tell you all that much, does it?
The other camera I looked at while I was there that impressed me was the Nikon D40, of all things. It's large by digicam standards and positively wee by DSLR standards, yet it fit my large hands surprisingly comfortably. The viewfinder is of decent size and quite bright for an entry-level camera, focusing and shutter noise are remarkably quiet, and the LCD screen is big and pleasing. Barring any undetected major flaws, I don't think this would be a bad option as a main camera for many photographers, and especially if my main camera was one of the big-dog D2's I'd pick this up in a heartbeat as a small, portable, carry-all complement to the larger body.
But it did highlight (if obliquely) one of the real strengths of the Pentax. Like a draft horse switching horseflies with its tail (again, I hope the good folks at Nikon will forgive my overly colorful locution), Nikon severely limited the lens compatibility of the D40 to try to encourage D40 buyers to stay away from pesky Tokina and Sigma et al. and buy real Nikkor lenses. The K10D, on the other hand, really makes sense with in-body IS (it calls its version SR, for Shake Reduction, unless I'm confused), because Pentax has the greatest range of body-lens compatibility of any manufacturer. You can't even autofocus on the D40 with an ordinary AF-"D" Nikkor, but you can get IS on the Pentax with any Pentax lens back to, and including, M42 screwmount lenses, regardless of what other automatic functions may or may not be compromised. For this reason, it really makes sense that Pentax chose to put its IS-type SR function in the body and not in the lens.
Posted by: MIKE JOHNSTON, thanks to Scott W.