Marks on internal glass of Canon 200-400mm f4L?

[dmaukbobcat]

**EDIT: the last 2 photos are the lens under less harsh light, for context, of how it normally appears**

**2ND EDIT: Added a couple sample shots of its performance in the field**

Recently I purchased a used Canon 200-400mm and it appears in good condition, except for something odd i noticed. This is my first big glass I have owned, so I am not sure if this is just an artifact of manufacturing. 

While cleaning the lens, I noticed that there is a mark inside one of the internal elements that is only visible when a very bright light is shown at an angle almost parallel to the front element. The mark appears circular and like a smudge from polishing, but it is invisible under any other lighting conditions (angle or intensity). Is this just a faint polishing mark from manufacturing, or is this something I should not be seeing? Note that the internal parts of the lens are so free from dust (outside of what is to be expected from manufacturing; dust in the photos is on the surface outside) that I doubt anyone has opened it up to attempt to clean the lens and has, as far as I know, never been serviced by anyone outside of Canon personnel. 

Sample photos; the close in shot of the tern is with the 1.4x teleconverter engaged as the tern flew overhead

 

[amfoto1]

That looks like a fingerprint on an internal element! Although I doubt it will do any harm to images, I might send the lens to Canon to have it checked out. It's an awfully pricey lens to not have it perfect!

Note: When I first saw the images, all the dust made me think it was really dirty inside or full of some sort of fungus. So I'm just taking your work that it's just surface dust that's highlighted by the light you are shining through the lens and is easily cleaned off. (I might have removed all that dust before taking photos of the problem.)

I couldn't see the spot you're asking about until I enlarged the image to their maximum size. But, yes, it's visible in the 2nd, 3rd and 4th images... especially when the larger versions of them are viewed. 

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7DII (x2), 7D(x2), EOS M5, some other cameras, various lenses & accessories
FLICKR

[dmaukbobcat]

Hello, and thank you! It was hard to get a photo of it, its invisible under almost all consitions except a very bright light... its more circular than a finger print, almost mechanical. The dust: thats as clean as I could get it; the bright light and macro lenses narrow aperture makes the dust look huge. For context, here is the lens under normal lighting:

 

[shadowsports]

Greetings,

Congrats on the acquisition.  Lenses do not come with dust, manufacturing artifacts or polishing smudges, etc from canon.  I'd send it in.  It probably served its previous owner well.  It will serve you also.  I'd want a clean bill of health, but that's just me. 

I see the center mark you are referring to.  I also see other circular spots.  Are those reflection anomalies or fungus?  I can't tell from the images.  I still vote for an inspection and precision alignment. 

Canon Precision Alignment | Canon U.S.A., Inc.  

[dmaukbobcat]

The circles are out of focus dust (bokeh from f2.8 aperture lens used to take the photo makes them look larger... it was reeeeallly hard to get a shot of the circulat marking.) heres how the lens looks under less direct, less harsh, light, with a different lens used to take the photograph

 

[shadowsports]

Looking much better now.  👍

[dmaukbobcat]

Thank you! Based on that less extreme photo, and considering the extreme lighting conditions needed to see the flaw, do you think I am overanalyzing it? I am worried because Canon's support page says that the 200-400mm is a retired product, and that they don't provide support for retire products... but when their service center reopens (its a holiday) I am going to call and clarify if that means they just won't repair it, but will still do cleanings/calibrations/etc... 

I do wonder if I am overthinking it, since it performs well: (examples)

1.4x teleconverter engaged, In-Flight shot of a tern right overhead; the AF certainly works!

[shadowsports]

Greetings,

You can check, but typically retired means we don't service it. 

But midwest camera dot com should 😀  I think you have solid service, repair and maintenance options available.  Those recent shots are great.  The detail is remarkable.  Canon recently patented a RF 200~500mm with internal 1.4x TC design.  Today CR said some big whites were going to be announced shortly.  The RF 100~500 was going to be my fallback, now I'm glad I waited.  If I can get something by July I'll be very happy.  

[jrhoffman75]

Products subject to repair support period| Canon

You can use Google translate. Doesn't look like Canon has established an end of repair period. Worth calling Canon repair.

[dmaukbobcat]

Thank you! On the Canon USA page, when navigating to the service page for the 200-400mm, it leads to a page stating that it is a retire lens and that it is no longer supported... do you know if the information you posted applies globally or just to Canon Japan?