Hi all,I know this aledged problem has been discussed a number of times but has it ever been established how the dust enters the lens. I have heard several plausible explanations:1. dust is sucked in under the front seal when the lens is extending - this can be prevented/reduced by using a filter 2. dust is entering from the side when the lens extends and contracts3. dust is nested inside a bad batch of lenses and shows shortly after taken into use 4. dust is entering from the rear of the lens 5. a combination of the above..?I own a dustless copy of the lens myself but feel reluctant to skip the filter (which has been on since day 1) in case the problem is related to the front seal...Anyone knows for sure?Thanks! Thomas(..and yes, I know that dust may not affect IQ but I prefer to keep the suckers out anyway...)

...just out of curiosity: why do you care about a few dust spots in the lens? Did you experience bad photgraphic results because of that? Do you also care about some dust on the dashboard of your car?Yes, I know, dust spots disturb the perfect look and finish of a (new) lens.Greetings, Michael

Hi Michael,Well, having seen some ugly pics of dust in the 17-55 I can assure you that the dust can accumulate to a lot more than 'a few dust spots'....and having spent a lot of $$ on this lens I would like to reduce the risk of my lens beeing filled with dust...Sorry, I dont quite follow your comparison of an expensive lens and the dashboard of my car...maybe its just meBR Thomas

From what I have seen in several threads discussing this issue, it is your #1 reason, and a front filter should solve your problem. I have had mine for over 2 years with filter always on, I went to very dusty places (deserts, sulfur-filled volcanos, etc), and have not experienced any dust-related problem. Hopes this helps, Fredtfddkwrote:Hi all,I know this aledged problem has been discussed a number of times but has it ever been established how the dust enters the lens. I have heard several plausible explanations:1. dust is sucked in under the front seal when the lens is extendingthis can be prevented/reduced by using a filter2. dust is entering from the side when the lens extends and contracts 3. dust is nested inside a bad batch of lenses and shows shortly after taken into use 4. dust is entering from the rear of the lens 5. a combination of the above..?I own a dustless copy of the lens myself but feel reluctant to skip the filter (which has been on since day 1) in case the problem is related to the front seal...Anyone knows for sure?Thanks! Thomas(..and yes, I know that dust may not affect IQ but I prefer to keep the suckers out anyway...)

if it happens it happens, I'd save your worry for something a little more worrying

Hi Fred,Thanks for your reply.That would explain why I havent experienced any dust problems until now and also encourage me to keep the filter onBR Thomas

Dust doesn't just have a small optical effect. The most important problem is dust getting into the mechanical mechanisms and causing wear. The most sensitive are the aperture and IS elements. I don't know whether these are dust sealed within the lens, but it's still worrying from a long-term reliability point of view.

I got my lens without any dust in it and ever since (3 months) it has never got in. I got a bad experience where I got to a beach in a windy day and lots of sand hit the lens and it got some sand in the focus ring. Very scarring thing to listen (and to experience). I used a small vacuum cleaner around the lens and it turned out as new again. But nothing got in the front element. Yet. I can be related with the use of a filter (UV or CPL, doesn't matter here).The zoom extension mechanism gives me creeps as it seems to be able to suck so much dirt in. But nothing so far. (I guess the fact I use an air blower every once and then helps here!)Regards and good luck!

I had a filter on mine which seemed to prevent dust getting in. I subsequently dropped my lens anf broke the filter. Since 77mm filters are kind of expensive I never got around to replacing it. Well, now there's a ton of dust in my lens.If it's still under warranty, will Canon clean it for free?

I found a link here or over at POTN that linked to an interesting page where this guy busts the seals and cleans his element himself. In that article he shows a couple oval slots on the front of the element (where the screws clamp the element down) that he thought where the clear source for the intrusion. I have left my UV on since day one and currently have zero dust, used it all the way up the coast of California, took maybe 1500 shots in very dusty conditions with no problemskeep the filter on and be happy:) -- Summer in Seattle!

I had a dozen or more specs of dust in my first 17-55 and Canon told me (at 30 days) to return it to my dealer. My dealer exchanged it (didn't really want to, but did) and my second one is now 13 months old and only has about three specs. I have never used a filter on a DSLR lens. My second copy is not as sharp as my first was. I figured this all out. The dust is designed in by Canon. It is a feature and not a fault.Just, kidding, but it seems that way from my limited experience.Gordon

Thanks for all your inputs...even though you seem to have different experiences with the lens I tend to believe that the problem may be related to the front seal. At least I havent heard of any instances of heavy dust problems with lenses that had filters on them from day one...so I guess my UV stays there for now as well...

Just send it back or drive to a service center. I don't know if it would really be worth the return shipping or the wait time without the lens, but it's up to you. I'm using a UV filter on my and no dust so far.

Here is the link:http://www.pbase.com/rcicala/1755_is_surgerythatkatmatwrote:I found a link here or over at POTN that linked to an interesting page where this guy busts the seals and cleans his element himself. In that article he shows a couple oval slots on the front of the element (where the screws clamp the element down) that he thought where the clear source for the intrusion. I have left my UV on since day one and currently have zero dust, used it all the way up the coast of California, took maybe 1500 shots in very dusty conditions with no problemskeep the filter on and be happy:) -- Summer in Seattle!

I just did this and it is incredibly easy! All you need is a really tiny flathead screwdriver and really tiny phillips head screwdriver. That, and whatever you want to use to clean the elements.You use the flathead screwdriver to pry off the decorative (and I stress decorative!) ring. I mean the piece of plastic cr@p that says "Canon Zoom Lens 17-55mm" or something like that. You'll see three tiny metal screws. Unscrew them and make sure you don't drop them into the lens. Just take the lens and point the front end down and make sure to catch the front element as it will just fall right out. Clean the rear end of the front element with compressed air or some optical paper. Do the same with the next element you see. Plop the front element back in, replace the screws, and put the plastic ring back on.The plastic ring that supports the front element is FULL of holes and grooves for dust to get through. I'm guess if you're clever enough with materials, you could plug all the holes and seal up the lens yourself. I'm not that clever.By the way, I believe the pictures are from Roger Cicala, the owner of lensrentals.com. Really nice guy!And no, I don't work for him!Dzung Phamwrote: Here is the link:http://www.pbase.com/rcicala/1755_is_surgerythatkatmatwrote:I found a link here or over at POTN that linked to an interesting page where this guy busts the seals and cleans his element himself. In that article he shows a couple oval slots on the front of the element (where the screws clamp the element down) that he thought where the clear source for the intrusion. I have left my UV on since day one and currently have zero dust, used it all the way up the coast of California, took maybe 1500 shots in very dusty conditions with no problemskeep the filter on and be happy:) -- Summer in Seattle!

Wow! You have a lot more guts than I do. However, I think all of those little holes are there to allow the air pressure to equalize when zooming. Without them there would be serious problems (like sucked out of allighnment elements). What COULD be done would be to make the holes a little larger, maybe reduce their number, and put micro filters inside each hole. That way the air would get through without the dust. Canon could do this, but it would cut into their profits. Also, the filters could be vacuumed with one of those tiny computer vacuums.Gordon

Hmmm, I just tried this, and while completely easy and successful for cleaning out the dust, I couldn't help but notice that the rotational positioning of the front element is critical as its angle creates an offset for the element - try undoing the screws (take a photo of their position before you do this!) and twist the front element. It moves back and forth according to the angle.So, seeing as I didn't take the precaution of taking a photo of the screw positions before undoing them, my guess is my lens is now in need of calibration. Suck. Let this be a warning to you all! Jon

I got my 17-55 back in April/May and put a Hoya filter on it the second it came out of the box.I now have one spec of dust that is only visible through the back of the lens when I shine a light through it. But the dust is not on the rear lens element but appears to be somewhere in the middle. My guess it came in through the barrel somewhere.In any event, I will send it back to Canon for cleaning before the warranty expires.

For those that think dust on the inner elements has no effect on photos:Michael Engelenwrote:...just out of curiosity: why do you care about a few dust spots in the lens? Did you experience bad photgraphic results because of that? Do you also care about some dust on the dashboard of your car?Yes, I know, dust spots disturb the perfect look and finish of a (new) lens.Greetings, Michael

Big Handswrote:For those that think dust on the inner elements has no effect on photos:That's not dust on a lens. That's dust on a sensor.... quite a different matter.If you trust yourself, then you can put the camera in bulb mode, and with a lens off, gently blow some air in with a blower bulb, and most of that will probably go away.... else someone will chime in with a safer way to clean it out.To the OP, I've had my 17-55 for almost a year now, and there is not a single spec of dust that I can see in my lens. From my point of view, associating dust attraction with a 17-55 is the most unsubstantiated rumor related to canon gear I'm aware of.