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Old Dec 28, 2008, 4:57 PM   #1
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Hello everyone. I just happened upon this site yesterday when I was looking for a simple explanation about lenses. There are some fantastic pics on this site and I look forward to learning from everyone here.

I love taking photos of birds and wildlife and had been using my Canon Power Shot S3 Is with a 12x zoom. It has many functions that I don't use and some I don't understand, but it takes great photos and I've used the zoom and the macro functions a lot.

My new camera is a Canon Rebel XSi, 12mp. It came with an 18-55mm lens and I bought a 55-250 telephoto lens too for Christmas. Now, I'm feeling a little disappointed with the zoom capability of the new lens. When I asked the clerks to explain the difference between the Power Shot's 12x zoom and the 55-250 lens, no one could explain it to me. I'm finding that my old cameratakes pics that are much closer.

I'd love some advice on what kind of telephoto lens I could buy that would take good close ups of birds...andpreferably be better than the one on my old camera.

Thanksso much!


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Old Dec 28, 2008, 6:41 PM   #2
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Hi Leslie and welcome to Steve's.

Sorry that you have found us while tring to solve an issue that has dissapointed you but hopefully you will find Steve's a good please for info and for more learning in the future.

OK, sounds like the store you went to really didn't have a grasp of the terms used in photography, you find that P&S cameras use a number such as 3x or 5x or in the case of the S3 12x. This is the relationship between the minimum and maximum focal length, and now here again there is more confusion so for the moment I'm going to refer to the 35mm equivalent as this is what a lot of people understand. The S3 has a 35mm equivalent of 36-432mm.

Now going to your new Canon, the lens you got is 55-250mm, however this is not the 35mm equivalent as the Canon XSi has a smaller sensor than a 35mm camera so you have to multiply the focal length by 1.6x. This means you get a 35mm equivalent of 88-400 so slightly shorter, but not a lot, than what you have with the 3S. If you had gone with a 70-300mm lens then you would have had 112-480mm equivalent lens.

OK so a little more information on this whole lens length thing. All lenses are measured in the same way (which is mm)but depending on the camera they are mounted on will affect the field of view that is obtained.

Now the S3 has a small sensor in relation to the XSi, but even that has a smaller sensor than a 35mm camera so let us use these 3 examples.

Now let's look at the wide end of the S3, this is a 6mm lens, to give a same filed of view (a shot that looks roughly the same) on the XSi then you would use a 22.5mm lens and on a 35mm camera you would be using a 36mm lens.

At the long end on the S3 the lens is 72mm, on the XSi you would use a 270mm lens for the same filed of view and on a 35mm camera it would be a 432mm lens.

So this is the reason that most people use a 35mm equivalent measurement as this makes it easier to compare the field of view you will get. However there are other things that are affected by different sensorssensor such as the depth of field (in basic terms how much is in focus either side of where you actually focus the camera, but I won't go into this now).

So to close let's look at the coverage you have now with the XSi, your 18-55mm lens has a 35mm equivalent of 28.8-88mm so at the wide end you are better than the S3's 36mm so this can be a lot better for landscapes, architecture etc, at with the 55-250 as already mentioned you are 88mm to 400mm so just a bit smaller than the S3. Overall this is a zoom range of 13.8x from 28.8-400mm but no one uses this term in the dSLR world really.

Don't give up on the XSi, there is a whole lot more that you can do with this over a S3 or any P&S but it does take some learning but if you spend a little time you will be very happy I'm sure.
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