Check your 11-24L for decentering!

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PhotographyFirst

Jan 30, 2015
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#1
I've been looking at many sample photos from the 11-24 at 11mm. So far I have spotted some copies with poor centering at 11mm. At $3000, you should be demanding perfect performance.

Here is one example. If I am incorrect about my observation, please let me know. Check the lower corners. On a 5Ds, this is going to be way worse.

https://www.flickr.com/photos/29823753@N02/16030615343/sizes/o/

If you need help with checking with centering, I have a 16-35L guide in the education section of my website which shows you how. It applies to all lenses.
 
#3
Your 16-35 guide is very nice!

Regarding the centering, I too can see very clearly the difference... Very unfortunately, it is a recurrent problem with many wide-angle lenses: they seem to always have better corners than others. And if you send it to Canon to service it, they return it as you sent it... :(

Perhaps that could be acceptable for kit lenses at 18mm or for the 10-18mm, but never for a 3000$ lens!
 
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#8
I'll test my copy soon, but I saw this on Dpreview yesterday have two notes on this - #1, this photo is from 2/14, so it's likely to be a prototype/pre-production model, and #2, the photo is not of a flat surface and the subject distance in the two lower corners is not the same. I'm not saying it isn't decentered, but this isn't a very good photo to determine whether it is or isn't decentered.

Also, Johan, that's a nice page on your site. I'll have to check it out when I have more time.
 
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#9
mackguyver said:
I'll test my copy soon, but I saw this on Dpreview yesterday have two notes on this - #1, this photo is from 2/14, so it's likely to be a prototype/pre-production model, and #2, the photo is not of a flat surface and the subject distance in the two lower corners is not the same. I'm not saying it isn't decentered, but this isn't a very good photo to determine whether it is or isn't decentered.

Also, Johan, that's a nice page on your site. I'll have to check it out when I have more time.
Click to expand...
At 11mm and that distance, I can't imagine it makes a difference. :)
Plus the whole left side looks a bit soft on the edge.

I've seen this in other shots, but maybe they all came from the same lens? Who knows. If true, then did Canon put out a bad lens for testing or did it get bumped and put out of alignment?
 
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#11
Also, if you do the centering test like shown on the website, make sure to do it wide open on the 11-24. I did it at f8 on the 16-35L because the corners are so soft wide open on a good copy that it is difficult to do the test for bad copies. :)

I really wish Canon comes out with a 16-35L III f2.8 with the f4 IS treatment. :)
 
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#12
mackguyver said:
I'll test my copy soon, but I saw this on Dpreview yesterday have two notes on this - #1, this photo is from 2/14, so it's likely to be a prototype/pre-production model, and #2, the photo is not of a flat surface and the subject distance in the two lower corners is not the same. I'm not saying it isn't decentered, but this isn't a very good photo to determine whether it is or isn't decentered.

Also, Johan, that's a nice page on your site. I'll have to check it out when I have more time.
Click to expand...

I also noted that this is not the best photo to test decentering. I'd suggest that anyone checking a lens for decentering to look at Roger Cicala's article.

http://www.lensrentals.com/blog/2012/05/testing-for-a-decentered-lens-an-old-technique-gets-a-makeover
 
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#13
You can also use a Zeiss Siemens Star Chart to test for decentering. Roger at Lens Rentals has a nice writeup - http://www.lensrentals.com/blog/2012/05/testing-for-a-decentered-lens-an-old-technique-gets-a-makeover

You can purchase one (Amazon, B&H, Adorama, ...) or find a freebie for download (https://www.google.com/search?q=zeiss+siemens+star+chart&tbm=isch)
 
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#15
dcm said:
You can also use a Zeiss Siemens Star Chart to test for decentering. Roger at Lens Rentals has a nice writeup - http://www.lensrentals.com/blog/2012/05/testing-for-a-decentered-lens-an-old-technique-gets-a-makeover

You can purchase one (Amazon, B&H, Adorama, ...) or find a freebie for download (https://www.google.com/search?q=zeiss+siemens+star+chart&tbm=isch)
Click to expand...

That's not a good method on Roger's part, because he assumes people have a test bench where the chart and sensor plane are perfectly parallel. It also seems like you have to test at a close focusing distance only. On an UWA lens, this would require a chart the size of a house to get mid to long field readings.

The method I describe on my website can be done without a proper testing facility.
 
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#16
Johan, nice website. Some really stunning landscape photos there!

"... After shooting the first roll of film, I opened up the camera to see how my pictures had turned out by unraveling the canister. To my surprise, I saw nothing and thought my camera was broken! Well, it turned out I needed the minor step of processing the film." : LOL!!!
 
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#18
pierlux said:
Johan, nice website. Some really stunning landscape photos there!

"... After shooting the first roll of film, I opened up the camera to see how my pictures had turned out by unraveling the canister. To my surprise, I saw nothing and thought my camera was broken! Well, it turned out I needed the minor step of processing the film." : LOL!!!
Click to expand...

Thanks. I still remember that moment like it was yesterday. :)
Something kids these days may never experience.
 
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#20
geekpower said:
Regarding the section on your guide about infinity focus, isn't the purpose of the "past infinity" part of the focus ring to allow for the effect of different temperatures on the lens?
Click to expand...

Yes it is.

And the TS-E lenses focus even further past infinity to give you more control over the plain of focus.
 
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