Quote:
Originally Posted by inacar
Thank you, for all your information. I shall experiment some more, but it seems if you are over the 300 range you can enjoy the benefit of IS without question.
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Ina,
Whilst I have no direct experience of Canon's IS lenses, I have a similar system to this in my Pentax body. You can get benefits from IS at much shorter focal lengths than 300mm. With a shorter lens, you may not see the benefit unless you are a LOT slower on the shutter speed. On a sunny day in Texas, your shutter speed may be so high that you aren't seeing the difference of IS on or off. Try taking pictures in darker conditions, get the shutter speed down, even with short lenses. If your shutter is slow enough, you'll see the difference.
The normal rule of thumb for hand-held shots on a full frame film camera is that the shutter speed should not be slower than 1/focal length. With a cropped size digital sensor the crop factor should also be taken into consideration.
So, if you are using a 50mm lens, you would traditionally not have gone slower than 1/50th of a second on a film camera without IS to get an acceptable result. If you are using a dSLR with a 1.5x crop factor sensor, this would mean it takes a steady hand to get a sharp shot at slower than 1/75th (i.e. 50 x 1.5) of a second. If your experiments with and without IS have been using shutter speed/lens combinations following this kind of rule, then you may well not see a huge difference.
There is much debate about how much improvement you can get with IS, but I think it's safe to say you should start seeing marked improvements between IS on and off at 2 stops slower than the rule of thumb.
So, with a 50mm lens, you would normally get an acceptable result hand-held at 1/75th of a second on a 1.5x dSLR without IS. If you use the same camera/lens combination in darker conditions such that the shutter speed is down to 1/16th of a second, then you should see the benefits of IS on or off.
I've taken a (stabilised) hand-held shot at 30mm focal length, on a 1.5x crop sensor, at 0.5 seconds (no, I won't post it, Chris will understand
), and had a sharp picture. There was an element of luck in this and it wasn't very repeatable, I just state this to show what can be achieved at shorter focal lengths.
Perhaps you just have too much light to see the benefits of IS. The answer is to move to gloomy northern Europe.
Duncan
Oh, and P.S. If anyone wants to start arguing that the crop factor doesn't make any difference to the amount of shake on the image, start a new thread.