Why is the 100-400 concidered a dust sucker?

Permagrin wrote in post #3069392
When I first bought my 100-400, I hated that lens for the dust issues. I had more problems with dust and it on my 5D than any combo I'd ever owned...and said so on POTN several times...

HOWEVER, over time, I realized a few things....the 5D is the dustiest camera I've ever owned, it just seems to gather dust and I've learned to live with it's foibles...(but not knowing about that didn't help the 100-400's review any)...

After several serious cleanings/rocket blowings of the 5D, I noticed a few things...the first being that I could use the 100-400 as much as I ever did with no noticeable dust accumulation.

The 100-400 DOES move the air a lot more in the camera chamber...Ollie did a test on here somewhere where it shows just how it can inflate/deflate a plastic bag, and the other types of zooms cannot do this...

So, my re-vamped opinion of the 100-400 is that while it does move the dust already in the camera, I don't think it necc. sucks in any dust into itself or the camera.

(btw, I'm still not a big fan of the lens, but am trying to give an honest evaluation of it's pluses and minuses...)

The way it is designed; their are gaskets to prevent the dust from going into the lens or camera.I imagine if a gasket cracked or dried out then you may have some problems.

RikWriter wrote in post #3068915
No, in fact, it's not. It may not have happened to you, but it HAS happened to some people. It may be, for that matter, sample-specific, but I've had two different 100-400s now and it has happened with both.

It happens to people who use the zoom as a pump instead of a lens: move the lens in and out slowly and there's no problem.

In that respect, this is an urban legend, as it happens because of the user, not because of the lens.

gjl711 wrote in post #3069594
Hmm... This is an interesting experiment and I believe I'll try it on my 70-300 when I get home from work. It would be easy to rubber band a sandwich bag onto the back of the tele-photo fully extended and then zoom in causing the barrel to retract. If there is an air path from the lens chamber to the back of the lens, the bag will inflate.

I think Ollie did the same thing and photographed it (you should post your results here)...he used a plastic grocery bag I think in his test..

the.digital.guy wrote in post #3068802
Many feel that the Push/Pull feature of the lens will suck dust into the lens.
I have owned mine for 2 years now and shoot sports and motor sports.
NEVER had a problem with dust.

10 months, ditto, no dust.

FWIW, I used my brand new 30D for 3 months, changing lens' frequently and never had any dust spots. Bought the 100-400 and used it everyday for a week, never removed it, and had a bunch of dust show up. Coincidence...maybe. In fact I got so nervous something was wrong with the lens I started this thread w/pics.
https://photography-on-the.net/forum/showthre​ad.php?t=297150
Turns out after I cleaned the sensor cover all was well. Not a big deal anymore, just more frequent cleanings. Your milage may vary.

I think some of your reasoning is a bit flawed there, rik. You're saying that because of the speed of the zoom (in your first post) that the 100-400 will suck in dust where the other won't? Um, o...k... Then you point out examples of using the lens on trips in different years where one of the differences is the fact you brought this lens and that 'proves' the lens was the problem? Uh. Hmm.
I use the 100-400 and never had that problem. True enough, I've had lots of dust, but I had it before the 100-400 and on a camera I'd never mounted that lens on!
I'm not trying to slam you, but if you're going to say dust is on your sensor was caused by using this lens - or in fact, try to prove anything - make sure there's a direct relation between cause and effect. I've read about this issue for some time and I've never seen anyone do a test where the data gathered can support the theory. Just because something seems like it is, doesn't mean it is.

Permagrin wrote in post #3069703
He used a plastic grocery bag I think in his test..

Was it a Wallmart of Tesco bag, as we all know the build quality of the apparatus used in the experiment can affect the outcome

Nope, I just found the thread...holy cow, it was a long ways back...(and quite acrimonious too ) It was a sandwich bag...

https://photography-on-the.net …hp?p=2148712&po​stcount=91

my 100-400 is over 7 years old and does not have a bunch of dust in it..

Dekka wrote in post #3069562
The difference is other people are saying it happens no more and no less significantly than any other zoom design - not that it never happens.

But I already debunked that in my personal case---it did NOT happen with other zooms, and has not happened with other zooms since.

the.digital.guy wrote in post #3069606
Seems that people who own the 5D have the most problems..........coul​d it be the camera attracts more dust for some reason?

It definitely does because of the size of the sensor.

Keith R wrote in post #3069700
It happens to people who use the zoom as a pump instead of a lens: move the lens in and out slowly and there's no problem.

In that respect, this is an urban legend, as it happens because of the user, not because of the lens.

Sorry, but that's an unwarranted assumption on your part. I don't "use the zoom as a pump," despite your contentions otherwise. Matter of fact, after what happened in Yellowstone, I made a concerted effort to move it in and out slowly in Alaska and the results were no different. I've also noticed more dust when I've used the 100-400 on my 5D at home here in FL...though, thankfully, this dust blew off with the Giotto, unlike the moist kind in the north.

RikWriter wrote in post #3069950
Sorry, but that's an unwarranted assumption on your part. I don't "use the zoom as a pump," despite your contentions otherwise. Matter of fact, after what happened in Yellowstone, I made a concerted effort to move it in and out slowly in Alaska and the results were no different. I've also noticed more dust when I've used the 100-400 on my 5D at home here in FL...though, thankfully, this dust blew off with the Giotto, unlike the moist kind in the north.

Rik, I never had good luck with my 1-4...I just think there are lemon copies...and people with excellent copies have a hard time believing that (I didn't keep mine because I was never happy with it).

I suppose in retrospect, I would feel the same about the 300 f4IS w/tc...some people say that the IQ is definitely worse than the 100-400 (I've seen tests too that seem to support this) but my comparisons showed exactly the opposite. I think it all eventually resolves down to poor QC by canon...and the consumers are, as usual the ones to pay.

I'm not sure what pumping up a plastic bag does. If you have a lens that can pump air into an expanding area, that means the air will flow in. If you seal the end of the lens, the thing isn't pressurising. Just the air is going somewhere else. Since the body is not a seal but a pretty good resistance to the movement of the air, I would have thought it would actually be going somewhere else - or are you inflating the bodies when you zoom?

I am also a happy 100-400 owner by the way. Use it an awful lot and get dust as much as with my other lenses. The body seems to be more of an issue for me. I find my 1D MkII is more prone to it than my 10D which seems very resistant to dust.

My recommendation is, if you want it, can afford it and have a reasonable use for it, buy it and enjoy the shooting. It is a sweet lens and the occasional sensor clean is hardly the end of the world.

BoySpot wrote in post #3070001
My recommendation is, if you want it, can afford it and have a reasonable use for it, buy it and enjoy the shooting. It is a sweet lens and the occasional sensor clean is hardly the end of the world.

Very good advice. That's why I still have a 100-400, despite the dust issues. It's a good, versatile lens that has very good IQ for its size.