Trying to decide between the IS USM and non-IS.

Besides the obvious IS. Am I gaining anything in optics for the increased price?

The subject matter I will most likely be shooting will be fast moving so I'm envisioning alot of panning.

I'm an "advanced amatuer" to the SLR market and trying to decide which Zoom lens will suit me best.

In case it matters, this is for the Rebel XT (350D)

$534
<IMG SRC="http://consumer.usa.canon.com/app/images/lens/70-300_isusm_586x225.jpg">
$179
<IMG SRC="http://consumer.usa.canon.com/app/images/lens/ef75-300_4-56iiiu_586x225.jpg">

The IS in mode two (for panning) works pretty good.

It feels super cheap and it's a pretty soft lens too. I used it to take pictures of basketball games and most of the time it was really dim in the gym. IS would have been nice but ya I just don't think the images look that good.

I sold it and ended up getting a Sigma 70-200EX, even without IS (Sigma doesn't have optical stabilizatio on this particular lens).

I love mine. I've never used the 75-300 version (lesser optics, older generation IS), but all accounts are the new version kills the old one.

"<a href="http://www.photozone.de/8Reviews/lenses/canon_70300_456is/index.htm">The performance of the Canon EF 70-300mm f/4-5.6 USM IS came as a total surprise.</a>"

<a href="http://www.the-digital-picture.com/Reviews/Canon-EF-70-300mm-f-4-5.6-IS-USM-Lens-Review.aspx">Another good review</a>

<a href="http://www.fredmiranda.com/reviews/showproduct.php?product=294">FM reviews</a>

Some samples:

<img src="http://panekfamily.smugmug.com/photos/56296209-M.jpg">

<img src="http://panekfamily.smugmug.com/photos/55477329-M.jpg">

<img src="http://panekfamily.smugmug.com/photos/59775217-M.jpg">

I'm now leaning towards the IS.

As for the lens, what do you plan to shoot with it? Do you need the 300mm (neither of the two is exactly stellar at the extreme end).

Can you be a bit more specific about the most common use you foresee for this lens?

I'm looking for a versatile lens that will be the only zoom lens in my case for at least a year. So, it has to be able to handle a number of situations 'well', not necessarily the best at one or the other.

&lt;EDIT&gt; The DP.com seems to like the 70-300 IS for my requirement above: "The very useful 70-300mm focal length will handle portraits, well-lit sports, wildlife and many, many other photo subjects well."

"The Digital Picture.com" seems to like the Canon EF 70-200mm f/4.0 L USM over the lense I liked if you can do w/o the IS and the extra 100 mm.
<IMG SRC="http://www.the-digital-picture.com/Images/Pic/Canon-EF-70-200mm-f-4.0-L-USM-Lens.jpg"><ul><li><a href="http://www.the-digital-picture.com/Reviews/Canon-EF-70-200mm-f-4.0-L-USM-Lens-Review.aspx">http://www.the-digital-picture.com/Reviews/Canon-EF-70-200mm-f-4.0-L-USM-Lens-Review.aspx</a</li></ul>

and plan for an 2x extender a little down the road if I can do w/o the IS?

$544
<IMG SRC="http://www.the-digital-picture.com/Images/Pic/Canon-EF-70-200mm-f-4.0-L-USM-Lens.jpg">
$289
<IMG SRC="http://www.the-digital-picture.com/Images/Pic/Canon-Extender-EF-2x-II-Teleconverter.jpg">

not to mention build quality.

But forget about using 2x with those lenses - image quality will be very disappointing, not to mention that neither of the lenses you chose will autofocus on XT with the 2x attached. Even if the converter won't report its presence to the camera, it will be too dark for XT to focus properly

I went with the 70-300 vs the 70-200/4L because:

1. IS - it can really make the difference between getting the shot and not if you're hand-holding.

2. Smaller and lighter.

3. No white "steal me" factor.

4. Only a small difference in image quality.

5. More reach.

6. Uses the same 58mm filters as my other two lenses.

Overall, for my uses, I prefer the longer reach and IS. Right now with the rebates at B&amp;H, the 70-300 is $535 and the 70-200 is $545, so price-wise, it's a wash. The L will probably hold it's value a little better. The L responds well to the 1.4x TC from what I've read, but then you're still at f/5.6 and slightly shy of the 300 and without the IS, so if it's the reach you're after, the 70-300 makes sense (to me at least).

I'd have to strongly disagree - difference is not small by any means. While a stop slower, the 70-200 f/4L produces results very similar to 70-200 2.8L, which is nothing short of excellent.

70-300 does fine for a consumer zoom, but is just not in the same league.

Color, contrast and sharpness are simply not there.

I haven't - just going by the general 'net consensus.

I've also had both the IS and non-IS 70-200 2.8L and replaced them with primes in this range.

Again, the 70-300 is a good lens for what it is, and the IS can be very useful, it's just that all 3 of Canon's 70-200 are much better in color and contrast, especially in backlit subjects and such.

Of course, that's just my subjective opinion - that's the thing about reviews on the net, everyone has his/her own criteria and requirements

always found myself at the long end of that lens. I needed the extra stop and the prime is way better in AF speed, tack sharp, smaller, not white, and image quality/color/contrast/bokeh is phenomenal. I don't use as much as I would like to but with summer approaching I plan to get out and use it at youth sporting events and portraits.