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Big news this week was the incredible benefit of Canon's image stabilization technology built into several of their telephoto lenses. More about that in a moment. The surprise for me was the significant gain in low-light photography that this translates to. For the picture above the camera was hand held for a half second exposure! Now I can't think that these 62-year-old hands are any too steady - but even were I younger, the rule of thumb has been that anything under 1/60th of a second is inadvisable for a hand-held camera - 1/30 and slower is definitely tripod time.

Keep in mind what this means to low light photography. Every halving of shutter speed gains you an F-stop in exposure. So if this picture were correctly exposed at F4.5 at 1/60, then every time you doubled the exposure time you could shut the F-stop down a notch - and each time you do that you gain depth of field and a slight improvement in overall quality so you are moving from 1/60 to 1/30, to 1/15, to 1/8, to 1/4, to 1/2. That's five F-stops.

Of course your subject has to be still. In this instance Don was sitting across the table from me at lunch and cooperated. The film speed was set at ISO 1600, I used an effective focal length of 112mm, and it was taken at F18 - the F-stop chosen by the camera which I had preset to half a second just to see what the results could be.

So - is this a little soft in focus? Yes. Blow it up and you notice this. But is it an acceptable image? Well, you be the judge. It is for me.


So what's all this about? My big buck gamble this week on lenses with image stabilization. I sent back the Quantaray 28-210 - Ritz, to their credit, gave me my money back with no hassle, less shipping costs, of course. Then I shopped around until I found the best prices on two Canon lenses - a 28-135 IS zoom and a 75-300mm IS zoom. These, combined with the Digital Rebel's standard lens - 18-55mm zoom - seem to me to cover all the territory and shooting situations I can imagine - and, of course, they double the price of the camera - but hey! ;-)

What this translates to in terms of effective focal lengths on the Rebel of 29-88, 45-216, and 120-480. (See earlier entry on why less is more in digital telephotos.) Nice amount of overlap and incredible coverage from reasonable wide angle - 29 - to (for me) unheard of telephoto - 480mm!

But the big decision here was whether or not to spend the extra bucks - and put up with the extra weight - of the image stabilization technology. This is especially true of the 75-300mm lens which Canon makes in three flavors. The stripped-down version (with the same optical quality) can be purchased for close to $100. That's a bargain! One with a quieter zoom motor and some other advantages costs about twice as much. And if you search, you'll find the IS (image stabilization) model for about $440. But right now not many folks have them in stock. The 28-135 IS can also be found for a little less - $400. I got both of mine from an outfit I have never dealt with before, but certainly came through for me - . They had the best price, had the lenses in stock, and didn't play games by either trying to sell me accessories at inflated prices, or charging me something ridiculous for shipping. (One outfit offered me normal shipping that should have cost about $16 for $80! That made their "low" price on the lens not low at all.) Buyer be very wary is the simple rule here.


When I got the lenses my first shock was their bulk and weight. I had read the specs, but I wasn't prepared for this. I had been using the stripped down 75-300 lens loaned to me by a friend and it is significantly lighter and less bulky. The extra bulk figures big when you shop for two things - filters (72mm filters are more expensive then 58mm ones) and a camera bag. (Camera bags are designed with lenses in mind that may be long, but aren't fat. These are fat. So in one of those bags with the adjustable partititions you can fit just two lenses where three are supposed to go.)

But that's the only downside I've seen so far. The IS is promoted by Canon as saving you two stops on hand-held telephoto shots. I think that's conservative. That is, the rule of thumb is that the focal length of your lens is a good indicator of the shutter speed. A 300mm lens should be used at no less than 1/300th a second - hand-held. Since that 300mm translates to 480mm on the digital camera, I am assuming 1/500th of a second as the minimum hand-held.

But with IS I could cut that 1/500th to 1/125th. And that would gain me two F-stops, and probably stop any normal subject movement.

At high noon this doesn't matter. But I want to take pictures of birds and they tend to be most active at dawn and dusk - that means low light. So while the effective focal length of 480mm may get me very close to a bird, the necessary high shutter speed of 1/500th may not work in the low light.

So i decided to try the image stabilization. I haven't had sufficient time to field test it with wildlife. But I'm sure it will deliver because what I had not anticipated was the incredible performance I would get in low light on the short end of the telephoto.

I don't pretend to understand how image stabilization works. I became a believer a few years ago when I bought Canon's 15x image-stabilized binoculars. The improvement was obvious. Press a button, the image quieted down, and the steadiness brought out detail you had missed. These are great for birds, but their real tests comes in astronomy which is always the toughest challenge for optics - how many stars can you see in the PLieades, for example - and they passed this test with flying colors. So I already had confidence in the magic of the image stabilization technology before I bought the telephotos mentioned.


But I was still pleasantly surprised. For example, before I tested it on the portrait at the beginning of this entry, I simply pointed it at a dimly lit corner of the room and got this. A little soft, perhaps - but think of those wonderful art galleries where they do allow photographs - but no flash photography and no tripods! And I've always been a big fan of available light - when Tri-X first came out with the fantastic ASA (ISO to you youngsters) of 200 I immediately went out and experiment with it by taking portraits by the light of a single candle.

Posted by Greg Stone at March 21, 2004 07:58 AM
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