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Author Topic: Canon EF-S 17-85mm f/4-5.6 IS USM  (Read 3774 times)

Techdaddean

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Canon EF-S 17-85mm f/4-5.6 IS USM
« on: May 13, 2006, 12:19:11 am »

I was wondering if anyone has had any problems like this with a Canon EF-S 17-85mm f/4-5.6 IS USM. I purchased the lens new from a local dealer in July of last year. Have taken some great shots attached to my 20D. But...

I had the opportunity to go to Tucson and accompany a group of city slickers on a cattle drive...in a dust storm. At the end of the 3 hour ride the lens was a total mess. Dust had gotten into the lens and was all over the lens elements. The focus and zoom mechanisms were gritty with dust.

Now, I've had a similar Pentax lens on a *ist-D that I've taken on the Baja 500, through the silt-beds and all, with nothing of the sort every happening. Of course Canon didn't cover this under warranty, even though it's under a year old. Yes, I know that my Canon is not an L-series lens, but is this really what I paid nearly $600 for? Anyone else have similar experiences? Would the 24-105 4.0L have faired better?

Thanks,
Dean
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gochugogi

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Canon EF-S 17-85mm f/4-5.6 IS USM
« Reply #1 on: May 13, 2006, 02:44:20 pm »

No zoom can be totally sealed as the elements inside move during focal and zoom operations and therefore must displace air. The worst are usually the nested barrel designs as they have more cracks to suck in air. My EF 28-135 IS USM was a real vacuum. After a few bad experiences shooting in big surf with a zoom--even my mirror was coated with salt and I didn't change lenses--I stick to primes under heavy dust and salt spray conditions. My EF 200 2.8L USM and 300 4L USM don't appear to have any problems.
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jani

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Canon EF-S 17-85mm f/4-5.6 IS USM
« Reply #2 on: May 15, 2006, 08:33:04 am »

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No zoom can be totally sealed as the elements inside move during focal and zoom operations and therefore must displace air.
Huh?

It should be possible to create a sealed system where you have internal movement and displacement of air, without the need of ventilation. Hydraulics and other closed-circuit systems would have a hard time working if it weren't possible with the relevant fluids and gases.

You do, however, get a problem if zooming/focusing changes the external dimensions of the lens, as with the 28-135 or the 100-400 L, unless the design can cope with changing air pressures (ref. pumps).
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abaazov

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Canon EF-S 17-85mm f/4-5.6 IS USM
« Reply #3 on: May 15, 2006, 08:55:39 am »

i've used my ef-s 17-85mm in africa, patagonia, and other somewhat dusty areas. never had a problem. other than very usual and basic lens cleaning, it hasnt required much else. very happy with this lens.
amnon
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jrayupchurch

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Canon EF-S 17-85mm f/4-5.6 IS USM
« Reply #4 on: August 12, 2006, 04:56:58 pm »

I have the same problem with dust getting between the front elements. I sent it back to Canon for repairs under warranty. It was repaired it for free with no questions asked. The other day I noticed the dust is back between the front elements. The 17-85 zoom dust problem is a poor design on Canon part. I have 2 eight year old Tamron zooms that have never had this problem.
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gochugogi

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Canon EF-S 17-85mm f/4-5.6 IS USM
« Reply #5 on: August 13, 2006, 11:49:50 pm »

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It should be possible to create a sealed system where you have internal movement and displacement of air, without the need of ventilation. Hydraulics and other closed-circuit systems would have a hard time working if it weren't possible with the relevant fluids and gases.

I invite you to design such a lens and, if it works well, is reasonably small and light and affordable, I'll be first in line to buy it!

I own two "sealed" L optics, e.g., 17-40 4L and 24-105 4L, and I can feel a blast of air out the rear when quickly zoomed or focused. The 24-105 is said to have a dust shield where the nested barrel slides in and out of the main barrel. A assume a filter-like skirt to help keep dust and moisture out but allow free movement of the barrel and some air passage (hence water and dust resistant rather than water and dust proof). I imagine a 100% sealed system would need more torque in the AF motor than a ventilated one and a larger barrel with air space around elements to allow quick displacement of air when zoomed or focused.
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jani

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Canon EF-S 17-85mm f/4-5.6 IS USM
« Reply #6 on: August 14, 2006, 07:04:45 pm »

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I invite you to design such a lens and, if it works well, is reasonably small and light and affordable, I'll be first in line to buy it!

I own two "sealed" L optics, e.g., 17-40 4L and 24-105 4L, and I can feel a blast of air out the rear when quickly zoomed or focused. The 24-105 is said to have a dust shield where the nested barrel slides in and out of the main barrel. A assume a filter-like skirt to help keep dust and moisture out but allow free movement of the barrel and some air passage (hence water and dust resistant rather than water and dust proof). I imagine a 100% sealed system would need more torque in the AF motor than a ventilated one and a larger barrel with air space around elements to allow quick displacement of air when zoomed or focused.
Hmm.

The 70-200 f/2.8L IS apparently doesn't displace any air at all.  I tried four tests to get a hint of moving air while zooming in and out very quickly, as well as changing focus very quickly, but got no indication of air moving in or out of the lens:

1) Lens next to the ear
2) Fingers with hair near the rear end of the lens
3) Wet fingers
4) Post-it note

I thought I felt something once or twice with the wet fingers, but keeping absolutely still also occasionally produced the same feeling, so I could only ascribe it to evaporation.

I repeated the experiment with my 17-40 f/4L IS, and I got the same results.

Perhaps my testing methodology is flawed, but there certainly is no blast of air with the 17-40. My guess is that you've got a bad lens there.
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Jan

RedRebel

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Canon EF-S 17-85mm f/4-5.6 IS USM
« Reply #7 on: August 23, 2006, 03:46:51 pm »

I noticed some dust in my sold 17-85 IS lens, but it wasn't a problem. However I can imagine that it can cause trouble if you are using this lens in a real dusty environment.

I don't know how canon solves this problem in their L lenses, but if the length of the lens changes, their will always be some air flow in and out the lens. The best way to solved it would be to seal the moving lens elements and create a small air release hole with a small hydrofobic filter. This is the way used in medical equipment. This way the air has a controlled way to enter/leave then lens and the filter avoids dust and water comming in.
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