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ARTICLE REALLY WORTH READING
#1
This is a very interesting article:





[url="http://www.lensrentals.com/blog/2011/10/notes-on-lens-and-camera-variation"]http://www.lensrentals.com/blog/2011/10/notes-on-lens-and-camera-variation[/url]





I think this may change the way we look at lenses, at least that is my case!
#2
Thanks for the link. Nice article. Nice to see some data on the subject.
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.
#3
[quote name='Vieux loup' timestamp='1317850148' post='12143']

This is a very interesting article:





[url="http://www.lensrentals.com/blog/2011/10/notes-on-lens-and-camera-variation"]http://www.lensrenta...amera-variation[/url]





I think this may change the way we look at lenses, at least that is my case!

[/quote]



The checks were done at the image center. This is hardly a valid approach to check the centering quality.
#4
[quote name='Klaus' timestamp='1317853784' post='12147']

The checks were done at the image center. This is hardly a valid approach to check the centering quality.[/quote]



True. But the article is not focused on centering issues (forgive the pun). Even without taking centering issues into account, there is already a measurable difference as we go from one lens copy to another, from one camera to another.



It's also why DPReview and you arrive at totally different conclusions for the same lens (e.g. Canon 100 f/2.8L IS):



From http://www.dpreview.com/lensreviews/cano.../page6.asp

"Just occasionally a lens turns up which delivers such implausibly good results in our studio tests that I have to go back and repeat everything, double checking all settings to make sure I haven't done something wrong. The Canon EF 100mm F2.8 L IS USM Macro is one example; but in this case when I repeated the tests, the results were if anything slightly better. There's little doubt that, all round, this is one of the very finest lenses we've seen - optically it's superb..."



From http://www.opticallimits.com/canon_eos_f...5d?start=1

"The resolution characteristic of the Canon L lens is very good although it did fall a little short of the high expectations that we had here."
#5
Nothing is impossible but there was no indication of a sub-standard quality in this tested sample.
#6
[quote name='Klaus' timestamp='1317853784' post='12147']

The checks were done at the image center. This is hardly a valid approach to check the centering quality.

[/quote]

They did describe their charts as follows:



Quote:The charts shows the highest resolution (at the center of the lens) across the horizontal axis, and the weighted average resolution of the entire lens on the vertical axis, measured in line pairs / image height.



While decentering might not affect centre resolution, it should affect average which would put lenses off towards the lower right of the chart. There's some data points which seem to show that - still "high" centre scores but reduced average scores.
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.
#7
One more argument to finally implement school marks system instead of exact numbers. I guess Klaus was talking about this long time ago.



A.
#8
[quote name='Klaus' timestamp='1317853784' post='12147']

The checks were done at the image center. This is hardly a valid approach to check the centering quality.

[/quote]





They have no r eason to falsify the results and they are well equipped and have better data on a "number" of lenses than virtually anyone else!
#9
[quote name='Vieux loup' timestamp='1318001949' post='12198']

They have no r eason to falsify the results and they are well equipped and have better data on a "number" of lenses than virtually anyone else!

[/quote]



But by testing in the center only you won't identify lenses that are decentered in the sense that their image plane is slightly tilted. These lenses usually still show very good sharpness in the center ... it's one of the borders that's off in this case.



-- Markus
Editor
opticallimits.com

#10
Are my posts invisible here? <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/tongue.gif' class='bbc_emoticon' alt='Tongue' /> Their charts also include an element which is a weighted average of the whole image. So if some border region is off, it should drag down the average.



Just out of interest, how would different types of element misalignment affect image quality? e.g. 1: if an element is on the correct plane but shifted off axis, 2: if an element centre is on axis but the element is tilted?
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.
  


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