Canon X zoom (compact) vs MM zoon (dslr)?

Question

I've currently got a Canon S3 IS, which has a wonderful 12 X optical zoom (48 X digital zoom). I'm going to upgrade to a DSLR, but want an equivalent zoom. So...

What MM lens do I need to get the same zoom capabilites at 12 X???

Answer 1

Actually your Canon S3 IS has a lens that is 36mm - 432mm in 35mm equivalent. There isn't an SLR lens that has that range.   The closest I know of is the Canon EF 28 - 300mm f3.5-5.6L IS USM. Otherwise, you need multiple lenses.  Forget everything you know about 'X'.  Learn to think in focal lengths.

If you go with Canon...  

Canon EF 24-105mm f/4 L IS USM and the

Canon EF 100-400mm f/4.5-5.6 L IS USM

These are the two closest lenses that minimize redundancy and also have Image Stabilization like your S3 does.  Now look at the total you would spend.  (Either on that first lens, or the two below it.)  You can get by a lot cheaper with getting the standard kit lens EF-S 18-55mm f/3.5-5.6 IS and the EF-S 55-250mm f/4-5.6 IS.  At 250mm, the 35mm equivalent is 400mm.  This is close enough to the 432mm of your S3 IS without having to break the bank.  You could also get a EF 70-300mm f/4-5.6 IS USM instead of the 55-250mm.  This will bring your range further than the S3 IS, but you'll have a gap in-between 55 and 70mm.

Answer 2

Usually with SLR lenses you don't want to buy anything with more than a 5x zoom ratio as that usually means they've made some sacrifices in quality to cram all that zoom in one lens. There are some SLR lenses with close to 10x zoom but I'd avoid them. There are some exceptions, but this is true most of the time.

The nice thing about an SLR is that ability to change lenses. This allows you to much better suit your camera to the situation at hand.

Usually (for general photography) you'll want two or three lenses - one wide-angle, one telephoto, and maybe a portrait lens. The above poster has some good suggestions for lenses so I'd take a look at them.