Quote:Magnesium is no better shield against high frequency - and in front of the plastic body is a metal bayonet. Also, the mirror box is not only plastic?
If I look at this explosion drawing, I see at least two parts potentially made of some cast or sheet metal, which are in between the sensor and the radiating HS drive of the Tamron - this could be enough to prevent banding.
![[Image: exploded.jpg]](http://www.dpreview.com/reviews/CanonEOS550D/images/exploded.jpg)
but it is unfortunatelly not....
It is - as you said, you've no banding problems with the 550 D - and the explosion drawing is exactly that body.
If you take the 5D II the mirror box is much wider and therefore free way for free beams.
When it comes to interference, there are two general classes: radiated and conducted. It could well be one leads to the other. I don't think we could rule out either, so assuming line of sight between two points may be far from the case.
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Quote:It is - as you said, you've no banding problems with the 550 D - and the explosion drawing is exactly that body.
If you take the 5D II the mirror box is much wider and therefore free way for free beams.
sorry, I thought that this explosion drawing relates to 5D3... 
 Well, you can compare those bodies for yourself, which one has the bigger mouth to suck in EMP. B)
Quote:Magnesium is no better shield against high frequency - and in front of the plastic body is a metal bayonet. Also, the mirror box is not only plastic?
If I look at this explosion drawing, I see at least two parts potentially made of some cast or sheet metal, which are in between the sensor and the radiating HS drive of the Tamron - this could be enough to prevent banding.
Magnesium is a very good shield against high frequencies, that's why WiFi antennas have to be behind a plastic body part, even though the rest of the body is magnesium.
Most of smartphone or laptop metal bodies with inbuilt WiFi are made of aluminium and not magnesium alloy. Couldn't find a source which says how good a material shields against HF radiation. But the lighter a material's density, the lower the resistance against radiation, that0s what I thought.
Quote:Most of smartphone or laptop metal bodies with inbuilt WiFi are made of aluminium and not magnesium alloy. Couldn't find a source which says how good a material shields against HF radiation. But the lighter a material's density, the lower the resistance against radiation, that0s what I thought.
Not to be downer on your theory but it's wrong! Anything metal/conductive will shield radio waves.
For example, the whole body of the Pentax K3II is magnesium, Pentax had to do away with the built in flash to house the GPS (under plastic) in it's place in order to receive satellite transmissions, they didn't want change the body design.
Aluminum foil is sufficient to block radio frequencies (screening) and is often used as such, magnesium has very similar characteristics electrically!
so, small update....i got lens from Tamron´s service center. They claimed that lens is in perfect condition and that problems are caused by Canon. My contra arguments were that they produced lens for FF canon bodies and that they didn´t mention in any document (handbook, guarantee or any other doc) that it can happen to get banding with AI servo or something similar, and akso that USM motor causes this problem. After that I was told to send it once again, they will reconcider issue once again.... camera is in caonc´s service last 3 weeks, cannot wait to get their explanation...
epilogue:
as already written, I send both pieces to respectable services...after second itteration from tarmon´s side, i´ve got an offer from their side to get full amount of purchase price back (they explained that lens is competely ok, but they cannot change behaviour of this lens/body combination under above described settings). I also got quite a discount for canon´s 70-200 II in the store where i bought tamron. I accepted it and I ´bought OEM lens. Relativ good solution, except that my intention was not to spend 550 EUR more, but it is nice piece of glas. After few shots I can also say that tamrons lens is very comparable with canon´s one, regarding IQ as well as AF and build quality. This part of the story was more or less predictable, and I must say that on the end Tamron was fair enough.
Second part of the story I did not expected. Yesterday I got my camera back, but that was few days after I changed my lens. In report from the Canon´s service is written that they exchanged some circuit board(s) as well as sensor, and that now the camera is ok. Now I do not have possibility to check if it is so while I do not have tamron´s lens any more. What I expected from C is that they do not guarantee for third party lenses and that´s it. And I wrote in my problem description letter to Canon that I got banding on 4 different camera bodies (3 of those are brand new), .they repaired main, what is with rest few 10000 that are sold world wide? I am now a bit confused.
Anyhow, I do not have the probmlem any more, but it is still a bti of mistery to me what is real cause....
Thank you all for attention and replies...
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