How do you tell a good lens (Canon)

[bricat]

Thanks William. As soon as I finished posting off I went and read another post somewhere that spoke about IS for inside a church!!!!! no flash!!!! Point taken and remembered. I must admit I did miss seeing the 10-22 and the 60 2.8 without IS. I think my point was "is there a lack of quality(glass)in these lenses that they need to put IS with them to compensate? Where on FF you have a choice with or without IS and price of course. After all this I have become more knowledgeable so I appreciate the imput from everyone. And my decision is EF-S 17-55 f2.8 IS. Cheers AND HAPPY NEW YEAR

[Tricky]

I think my point was "is there a lack of quality(glass)in these lenses that they need to put IS with them to compensate?

Image stabilisation (IS) doesn't improve image quality in any way, it just helps compensate for handheld motion at slower shutter speeds. As such, you might struggle to hand hold a lens at 1/30sec without IS, but with IS you should be fine. Remember that the shorter the focal length, the slower the shutter speed you should be able to hand hold. A basic rule of thumb they taught me at school 25+ years ago was 1/focal length, ie with a 50mm lens you can hand hold 1/50 without a problem. As such, a 10-22mm ultra-wide lens should be OK at 1/10sec at the wide 10mm end (at which point you don't really need IS). Remember also that with a 1.6 crop camera (such as the 7D), you need to multiply by 1.6 (ie 10mm become 16mm, so slowest shutter speed would be 1/15sec). In reality, I find I can use a slower shutter speed than the above rule of thumb, particularly if I have time to regulate breathing or lean against something.

As an alternative to IS, you can buy a faster lens, eg F/2.8 rather than f/4.0. This means that your 1/30 shutter speed (difficult to hand hold) doubles to 1/60sec (which should be fine). You also get better background blur, though the downside is that you may not want to shoot at f/2.8 all the time and would prefer IS at a smaller aperture.

Have fun with the 17-55, its a well thought of lens.