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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses
Thread started 15 Oct 2006 (Sunday) 13:50
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CANON 100-400 LENS

 
Olli
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Time to make some scientific experiments.

In the attached picture you can see how much air pumping will create into one liter (clean) plastic food pouch (note the double rubber ring sealing :D). Somehow this amount of air needs to get in and out during every pump. :confused:

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Oct 21, 2006 03:26 as a reply to post 2148644

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condyk
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:lol: :lol: :lol: Nice Olli. I just think if someone feels they will worry about dust then buy something else; if someone else feels they won't worry about dust then get the IS L. No big deal. I don't like the pump action and I also feel the sharp in and out pumping is more hectic for any dust than a standard zoom approach so I doubt I'd buy another. Not right. not wrong. just a vibe. Hell, if people are really worried get a prime.

Oct 21, 2006 03:35

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malla1962
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Olli wrote in post #2148712external link
Time to make some scientific experiments.

In the attached picture you can see how much air pumping will create into one liter (clean) plastic food pouch (note the double rubber ring sealing :D). Somehow this amount of air needs to get in and out during every pump. :confused:

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LOL I like it,that thing moves more air than a Dyson vacume cleaner.When you shoot a air show and pump the thing like a skeet gun any dust in there is blown all over the place.I had this lens for about 14 month and it got used a lot at airshows,shoot a jet at f8 and you don't see the problem shoot a prop plane at say 1/160th f16 thats when I seen the problem.A mate of mine saed I was careless when changing lenses and he was very carefull{I am very carefull with all my gear by the way}.he was saying he has never had to clean his sensor in 2 years,guess what?he got a 100-400 within 1 week he is ordering sensor cleaners lol.at the end of the day if you change lenses dust will get in there and if you pump the lens like I did that dust has to go somewere.:D

Oct 21, 2006 03:43

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Keith ­ R
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Olli wrote in post #2148712external link
Somehow this amount of air needs to get in and out during every pump.

And?

If you've got the most rudimentary understanding of phyics you know that the air within the lens has to go somewhere when you zoom it - otherwise you've got a shock absorber, not a lens.

It make prerfect sense to vent the air into the camera body - or you've got to have a hole in the lens that would be open to the elements

And the fact that it does its "breathing" into the camera also proves that the lens can't be sucking dirt in from outside - if you've got a dust problem, it was there before the lens was.

Let's not forget either, that any lens that extends the way the 100-400 does and by the same amount - whether slide zoom or ring zoom - has to move the same amount of air.

Oct 21, 2006 07:45



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Olli
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Keith R wrote in post #2149073external link
And?

If you've got the most rudimentary understanding of phyics you know that the air within the lens has to go somewhere when you zoom it - otherwise you've got a shock absorber, not a lens.

It make prerfect sense to vent the air into the camera body - or you've got to have a hole in the lens that would be open to the elements

And the fact that it does its "breathing" into the camera also proves that the lens can't be sucking dirt in from outside - if you've got a dust problem, it was there before the lens was.

Let's not forget either, that any lens that extends the way the 100-400 does and by the same amount - whether slide zoom or ring zoom - has to move the same amount of air.

Keith, there is something I don't understand in your answer.

As the camera body does not have "elastic lungs", the air "breathed" by the lens must get in and out from the space defined by the (moving) back element of the lens and the space inside the body where the mirror is moving. Where is the leakage, I don't now (and I'm not going to submerge my camera body into the sink to see where the bubbles are coming). That air is the same air we are breathing - and that air can be dusty. So how come this dust can not be sucked into the camera?

Oct 21, 2006 08:23

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DAMphyne wrote in post #2131408external link
If you have ever worked in a dark room or scanned film, you would know that dust is the big enemy of film also.

Film was exposed once, developed and fixed once and then store or throw away. Sensor is yours for the life of your camera. Scary...

Oct 21, 2006 08:39

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Mick ­ Emmett
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Keith R wrote in post #2149073external link
And?

If you've got the most rudimentary understanding of phyics you know that the air within the lens has to go somewhere when you zoom it - otherwise you've got a shock absorber, not a lens.

Mmmm! Sorry but you would have a "Spring" Now if you were to fill the lens with oil and make it so it had to travel through a series of small holes to get from one side to the other then you would have a damper ;) come to think of it that would be a good idea to see where the air was going :D :D :D

What is Phyics anyway? ;)

Oct 21, 2006 10:42

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Olli wrote in post #2148712external link
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Oct 21, 2006 11:53

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Olli wrote in post #2149148external link
As the camera body does not have "elastic lungs", the air "breathed" by the lens must get in and out from the space defined by the (moving) back element of the lens and the space inside the body where the mirror is moving. Where is the leakage, I don't now (and I'm not going to submerge my camera body into the sink to see where the bubbles are coming). That air is the same air we are breathing - and that air can be dusty. So how come this dust can not be sucked into the camera?

If I understand physics correctly, if there was no air entering the lens, then when we zoomed out, it would snap back on itself because of the vacuum it just created. Thanks for the test Olli...

Oct 21, 2006 13:16

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Mick ­ Emmett
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Permagrin wrote in post #2149968external link
If I understand physics correctly, if there was no air entering the lens, then when we zoomed out, it would snap back on itself because of the vacuum it just created. Thanks for the test Olli...

Isn't that what I said?

Oct 21, 2006 14:35

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CyberDyneSystems
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Olli wrote in post #2148712external link
Time to make some scientific experiments.

In the attached picture you can see how much air pumping will create into one liter (clean) plastic food pouch (note the double rubber ring sealing :D). Somehow this amount of air needs to get in and out during every pump. :confused:

Olli that's awesome! :)

Now if anyone has a Bigma and is willing to be honest about it, you'll see that the Bigma's extending zoom action will produce the saem results, just with a twist of the ring instead of a push pull.

Again, there is no doubt in my mind that any zoom lens that extends it's length as it zooms may be moving air, the point is they all do. Puch pull or twist has no bearing on the internal movement of air.

Oct 21, 2006 20:02

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Olli wrote in post #2148712external link
Time to make some scientific experiments.

In the attached picture you can see how much air pumping will create into one liter (clean) plastic food pouch (note the double rubber ring sealing :D). Somehow this amount of air needs to get in and out during every pump. :confused:

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Good show Olli !:D

Oct 21, 2006 20:32

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Permagrin
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Mick Emmett wrote in post #2150192external link
Isn't that what I said?

Oh, Mick, honestly I've been away from this thread...I didn't know you said it but I'm glad someone else did ;)

Oct 21, 2006 22:35

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hello,

i have a 100 400 L lense, among others.
i have been having problems with dust in my eos 1d mk2 (you could not see the picture for the dust). i once had to paint out over 200 of the blighters because the picture was for publication. Sent back to canon twice in two months for cleaning, she is only five months old and the camera was delivered with dust spots!!!!!!

I asked canon how this could be seeing as i only use it maybe twice a week and i am extremely careful on lense changes.
I have told them that i have a small amount of play on the mount when the lense is connected and also i can move it away from the body maybe the width of a piece of paper (only on very close inspection though).
all of you with 100 400,s try it to see if you can do it to.
This i am certain wil not only allow dust in but also wreck the ability of the camera to accurately focus. I have read that this play was normal, but having now recieved the 400d and connected the 100 400 lense to it i see that it is not normal. The 400d is rock solid. no play at all.

They have responded saying that it sounds as if the lense mount is faulty and the guy i spoke to in the tech department was audibly shocked when i told him the problem. "its loose!", "it actually moves!" were his words. he told me to send it back to them straight away.
If canon give it back to me in the same condition then i have told them i will demand a refund. i am not paying this money for supposed high quality camera body with a faulty lense mount!!!! After all everything else on the camera is precision engineered.it is like saying that a ferrari is supposed to have a knocking sound on the front right wheel. i dont care, i dont like it and it does not fill me with confidence.

Has anyone heard this response from canon about dust on sensors and has anyone had a lense mount replaced on an eos 1d mk2 and did it solve the problem?

thanks for your time and any answers.

Oct 29, 2006 15:01



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canonloader
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Is that the only lens that's loose on that camera?

Oct 29, 2006 15:20

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