I was just looking at a 17-55 at the local camera shop today and taking some test shots.

From my preliminary ganders at the test shots, It is an optically terriffic lens. I'll likely wind up purchasing one.

One thing that surprised me though, is that this lens is designated as "IF" so Imagine my surprise when I noticed the front of the lens extending when zooming back and forth!

Is there more than one model of the 17-55? Also, if I'm going to be plunking that much money down for a lens that is "IF" - I want something that is entirely enclosed withing the barrel so that it is more resistant to dust/moisture etc.

I'm curious what sorts of adverse conditions people have used this lens in, and if they have experienced any problems with dust/moisture getting inside the lens.

Oobie , that backwards and forward thing is propably the zoom, which is different to the focus. I'm not completely sure what I have said is correct, but the two functions are separate and the focus is most likely internal. Gary

Usually, when a lens focuses, it may rotate and/or move front or back (you will notice that the front of your lens will extend just like 18-55 D50 kit lens) at the top portion of the lens. With internal focusing, this does not occur. Nothing extends. All the focusing is done inside and the only thing that will even cause the lens to extend is when you move the zoom ring.

Now, if you're saying that the lens barrel is extending when focusing, then that's something I was never aware of with 17-55s.

edited: I guess my first line was being misinterpreted horribly.

Edited by BryanP on Dec 26, 2005 at 11:59 PM GMT

"I have not seen any lens that zoom without having the lens barrel extending."

Uh I can think of many, the 70-200/80-200, 120-300, 28-70, the list goes on.

Yeah many lenses zoom internally as well as IF as Joshua listed some examples.

This brings me to ask if in fact the 17-55 does extend the barrel to zoom. If it does I may reconsider my decision to buy one and just get the 28-70, although I was looking forward to the wide of the 17.

Hmmmmm....

thebeephaha wrote:
"I have not seen any lens that zoom without having the lens barrel extending."

Uh I can think of many, the 70-200/80-200, 120-300, 28-70, the list goes on.

As I stated, I personally haven't /seen/ any. I didn't say they don't exist. I've been only recently buying lenses so I haven't gone through all the different types.

The 17-55 does focus internally , but the zoom does work by extending out by about an inch at 17mm and retracts for 55mm .
Buy it you won't regret it .

Brian

IF is "Internal focusing". It has nothing to do with zooming..

Thanks all for the info. I guess for some reason I thought "IF" meant the entire thing was enclosed and there were no visible moving parts.

The test shots I took really are great though, and I may wind up going for this lens anyway.

I have my 18-70 up for sale and will likely pick up a 17-55 once that goes.

oobie, it is an internal focusing design but the front element does move in and out slightly as the focal length changes. it is shortest at 35mm.

That is Coooool Norm!!!

thanks...though taken with my crappy point-and-shoot and now that i look at it, the white balance is off!

Snappy illustration

Yeah... it extends while zooming... but that's no reason not to get it (or at least a silly reason). It's an excellent lens.

FYI, the 28-70 does the same thing.

You don't notice it if you have the lens hood on. I love mine.

-jason m

The extending thing is not a problem.
The lens is SUPER sharp. You won't be sorry with it.