Upgrading my lens, can't decide what to upgrade to.

[Black_Dog]

I bought the EF-S 17-55mm f/2.8 in November. Zero regrets. It's the best all around lens I've ever used. One of these years I plan to move up to ff and I won't be able to take this lens with me. But I doubt at that time I will get rid of my crop-sensor bodies, so this lens will still have a place in my camera bag. I determined to get the best glass for the body that I own now (which is the EF-S 17-55) and cross the FF bridge when (or if) I get there.

[jrw]

17-55 f2.8 can best be thought of as an 'L' lens for IQ, but not for weather/dust&nbsp;sealing. Don't have it myself, but some people I know do and swear by it, not at it. Have played a little bit with&nbsp;theirs and found it quite&nbsp;nice, but shoot mostly FF myself. Tamron 17-50 owner I know mixes swearing by it with at it.<br><br>17-40 would not fit my definition of ideal walk around lens due to short focal range, distortion on wide end, and the previously mentioned AF curve which others have found as well so I have just assumed it is the nature of the beast. My usage is for landscapes on a full-frame body with narrower apertures. On a crop body it would still create perspective distortion of close subjects making it a non-flattering portrait choice. With the sensitivity of some subjects to their facial features it could come down to how fast can you run.<br><br>On the 70-200 front, I'd recommend the IS versions as well. Have f4 and f2.8. Won't be selling f4 version as the weight and&nbsp;size&nbsp;difference is very noticeable and it is an excellent daytime hiking and sports&nbsp;lens. Bring out the big gun for low light conditions, portraits.<br>Recommend the IS as an f4 IS lens can capture shots of still subjects with longer exposures than an f2.8 non-IS lens. If your typical&nbsp;subject with this lens&nbsp;is moving then aperture is more important to reduce shutter time. Ultimately,&nbsp;your intended&nbsp;use of&nbsp;a lens&nbsp;will be the best guide to selection.