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Author Topic: Lens length  (Read 2598 times)
avanides
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« on: January 18, 2006, 05:52:00 PM »
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As I don't often have a chance to browse camera stores, I do most of my shopping online, which has some restrictions (as far as I'm concerned).

I have one L lens (17-40) and absolutely love that all the zoom movement is internal, without any rotation of the front element. On the cheap lenses I began photographing with, the lens would vary in lenght according to the focal length setting, and the front elements would move all over the place, making circular polarizers a pain to use.

 I can't seem to find under specifications on places like B&H saying whether a lens has this "feature" or not. I've been looking at the Canon 28-135 IS, but am stumped. Does anyone know if the lens functions similarly to my 17-40 as described above?

Sorry if this seems like a pathetic question, but sometimes its those small things that pester us.
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boku
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« Reply #1 on: January 18, 2006, 07:12:47 PM »
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If I recall, the front on that lens does not rotate, but the lens does extend appreciably as it is zoomed. Over time, there is a tendency for the mechanics of that lens to "work in" and loosen. That can lead to "zoom creep" if you point the lens upward or downward (if not hand held) due to the effect of gravity.
« Last Edit: January 18, 2006, 07:13:05 PM by boku » Logged

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61Dynamic
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« Reply #2 on: January 18, 2006, 07:49:51 PM »
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I've used that lens a few times. It does not rotate when you focus (internal rear focusing) but it does extend when you zoom in.

As boku mentioned, it does creep quite a bit.


They way you can tell is by looking at Canon's website. There will be a series of icons at the bottom that indicate the lenses features. Since their site is poorly designed, I can't find the key to those icons where you can get detailed info on what each means. I know it exists, but don't know where...
« Last Edit: January 18, 2006, 07:52:25 PM by 61Dynamic » Logged
avanides
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« Reply #3 on: January 18, 2006, 11:35:06 PM »
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Thanks a bunch.

Its not too reassuring to hear about the loosening up -- that happened with a poor poor quality Sigma lens of mine, and had some real issues when I was using it. The price increase is pretty drastic when stepping up to the 24-105 L ... maybe I should save my pennies and profit in the long run.
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francois
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« Reply #4 on: January 19, 2006, 02:38:04 AM »
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Quote
Thanks a bunch.

Its not too reassuring to hear about the loosening up -- that happened with a poor poor quality Sigma lens of mine, and had some real issues when I was using it. The price increase is pretty drastic when stepping up to the 24-105 L ... maybe I should save my pennies and profit in the long run.
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Mine also experienced creep and after a couple of years of use it became annoying, especially with a lens hood and/or a polarizer attached. The focus ring and zoom ring also developped a fair amount of play. I sold it but I would say that it was a nice walk-around lens. The 24-105 is a big step up in term of price, I agree but its contruction is really above the 28-135.
I noticed that my 28-135 produced much warmer colors than my other lenses ... a moot point with digital cameras but with film it was very noticeable.
« Last Edit: January 19, 2006, 02:39:50 AM by francois » Logged

Francois
Lisa Nikodym
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« Reply #5 on: January 19, 2006, 03:38:21 PM »
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I have the 28-135 IS lens, and never had a creep problem with it (and yes, the front element does not rotate as you zoom).  However, images taken with it were always very fuzzy in the corners (even after sending it back to Canon for repair after it got *really* bad).  Some particular 28-135 lenses seem considerably worse than others in that way, and mine was quite disappointing.  If you're thinking about buying one, check the image quality in the corners after you get it and be prepared to return it if it's not up to your standards.

Lisa
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jani
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« Reply #6 on: January 19, 2006, 06:16:59 PM »
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I also had a EF 28-135mm, and can agree with what the earlier posters have mentioned.

I'd also like to point out that the 28-135 does not have dust and moisture proofing, so after a while, it tends to accumulate dust specks inside. The main culprit is the "pump effect", from zooming in and out.

If there is much dust, this will reduce contrast, although it will only rarely be directly visible.

I sold mine with a few dust specks that didn't have any visible impact.
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Jan
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