100-400 f/5.6 L IS USM lens and dust

[Tom Friedel]

I just bought thiis lens used on eBay, and the inside lens is full of dust. I am told that this happens normally with this lens, because of the push/pull mechanism, and should not be a concern and should not affect the shot. The seller is offering to take back the lens. What do people think? It makes some sense that if you pull the lens, air has to enter the lens, and dust could enter.
thank you,
tom friedel

[Roger Clark]

Yes, and that means dust gets into your camera,and thus higher probability of getting onto your sensor.

I have a 100-400 (bought in film days) but no longer use it (mine is too soft too). I now use a 300 f/4 L IS: it is sharper, even with a 1.4x TC. Tomorrow I should get delivery of a 300 f/2.8 IS. ;-)

Roger

[Doug West]

Tough call. The first thing I'd do is see how sharp it is. Some of the 100-400's have been known to be soft
at 400. If the lens is sharp and the dust isn't interferring with the image, you should be okay.

On the other hand, if it really is "full of dust", that would still bother me, just because I know its there and
I would always be looking at it.

Should you send it back...yes and no...I'm such a chicken :)

Doug

[Jonathan Michael Ashton]

I have had my 100-400L IS two years plus and it isn't full of dust and it isn't soft either. I don't think I am an exceptional case.
Jon

[Ken Watkins]

I had the same problem with my 100-400 , so I had it cleaned by Canon, it soon got dust inside again. Mine was also soft at the long end. I also substituted it for a 300m F4 very sharp and very light a wonderful carry about lens for safari work, and still good with 1.4X.

[Arthur Morris]

Yes, and that means dust gets into your camera,and thus higher probability of getting onto your sensor.Roger

That is a stretch at best... I have yet to ever see dust inside that or any other lens affect an image. I have owned five 100-400s over the years. They were all sharp at the long end. I just wish that they were a bit more rugged (especially when I drop them!)

[Roger Clark]

That is a stretch at best... I have yet to ever see dust inside that or any other lens affect an image. I have owned five 100-400s over the years. They were all sharp at the long end. I just wish that they were a bit more rugged (especially when I drop them!)

Simple test:
Take the 100-400 off the camera, and with no rear lens cap hold the back end up to your cheek. Now zoom the lens back and forth and feel to air rush against your cheek. It is not dust in/on the lens elements that is a problem with the 100-400, it is the dust that gets inside the barrel and through zooming action gets pumped into the camera and then on your sensor. On my first DSLR (a Canon D60) I used the 100-400 and had continual dust problems with its use. Once I stopped using the 100-400, I rarely have dust issues, even 2 weeks in a dusty environment in Tanzania I only got a couple of dust spots having to clean me sensor (1D2) a couple of times. Of course dust on the lens elements adds to flair too.

Roger

[Arthur Morris]

I always had dust problems with my cameras before I went to all MIII bodies with whatever lens I used. Most sensor dust is comprised of almost microscopic particles and is present everywhere... I would love to see a scientific test to prove that you are right. Your experience, is however, what it is. As far as lens flair, is that when the lens does something in an extravagant manner, or did you mean "flare." :)

[Roger Clark]

I always had dust problems with my cameras before I went to all MIII bodies with whatever lens I used. Most sensor dust is comprised of almost microscopic particles and is present everywhere... I would love to see a scientific test to prove that you are right. Your experience, is however, what it is. As far as lens flair, is that when the lens does something in an extravagant manner, or did you mean "flare." :)

Artie,
Oops, of course flare! Flair is what I get when I type without my reading glasses!

All lenses have flare, even at great distances from a bright source. While it becomes most obvious when sunlight is incident on the lens, it is there in every photo and reduces contrast (part of my job on spacecraft is evaluating the performance of optical systems: I have also ray traced optical systems and hand ground my own telescope mirrors). Poor polishing methods, for example, leaving micro-pits increase flare, as does dust. Another example: pictures of stars showing brighter stars as larger is due mainly to the lens flare, not that bright stars are actually larger. Any dust on the optics is detrimental at some level.

Here is an article describing my lens changing method for minimizing dust on the sensor:
http://www.clarkvision.com/photoinfo/dslr.changing.lenses
If I adhere to this method, I rarely have dust issues, even in dusty environments, and with all the DSLR's I have routinely used (D60, 10D, 20D, 30D, 1D2). For example, I have not had to clean any dust from my 1D2 or 30D this year. and I've taken thousands of images on multiple trips in the US and Europe.

Roger

[Arthur Morris]

Thanks for sharing your thoguhts and technique with us.

[Arthur Morris]

One final thought: I have kept thousands of images created with various 100-400 lens and sold hundreds of the (both film and digital) I have never noticed a single negative effect that could be attributed to dust inside the lens. Same goes for snow (and the resulting water drops) that got inside the lens during a snowstorm at Bosque. That was of course a major inconvenience as I had to send the lens in for servicing but the images were all fine. I am a believer in results.

[Maurice Allen]

Didn't want to start a new topic, but I am on the fence. I have used the 100-400 and now the 400 5.6 prime, really would like a more experienced opinion on what lenses I should buy. I shoot wildlife, water sports, ect. and really like the ease of framing with the zoom. Any help would be appreciated. Maurice

[Arthur Morris]

Hey Maurice, This thread should be of great interest to you:

http://www.birdphotographers.net/forums/showthread.php?t=14042