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Author Topic: mixed up measurement figures ?  (Read 4784 times)
macrobild
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« on: September 21, 2011, 10:58:45 PM »

This a comment for this page on the website
Your measurements of the Canon 70-200/2, 8IS mk2 is different from http://www.photozone.de/canon_eos_ff/510-canon_70200_2is28?start=1 and http://www.slrgear.com/reviews/showproduct.php / product/1316/cat/11 measurement. I have the  the old and new Canon 70-200/2,8is   and without exaggeration I can say that MK2 is better than the MK1 in terms of resolution and contrast.
Have you mixed up the measurement results from the two lenses?
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Nicolas
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« Reply #1 on: September 22, 2011, 05:34:29 PM »

Hi,

Thanks for bringing this potential mistake to our attention. But, after checking with all our experts in the lab, there isn’t really a mistake.

Indeed, the review  was a bit harsh with the new version of the Canon EF 70-200mm f/2.8L IS II USM and we modified it: http://www.dxomark.com/index.php/News/DxOMark-news/Canon-EF-70-200mm-f-2.8L-IS-II-USM-measurements-and-review.
But, overall the Mark 1 has a slightly higher and more homogeneous resolution. So, it scores better on a full frame camera, like the Canon 5D Mark II used in the review.
But, as we also added to the review, if you make the same comparison on a APS-C, it’s the Canon EF 70-200mm f/2.8L IS II USM that comes out slightly ahead. This may be the reason why the results are in other reviews made on other cameras.

So, what it means is that both lenses are really really close, and if you have a full frame it is better go for the older version and if you have an APS-C the newer version is a better choice.

Axel from DxO Labs
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macrobild
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« Reply #2 on: September 22, 2011, 08:49:14 PM »

Hi,

Thanks for bringing this potential mistake to our attention. But, after checking with all our experts in the lab, there isn’t really a mistake.

Indeed, the review  was a bit harsh with the new version of the Canon EF 70-200mm f/2.8L IS II USM and we modified it: http://www.dxomark.com/index.php/News/DxOMark-news/Canon-EF-70-200mm-f-2.8L-IS-II-USM-measurements-and-review.
But, overall the Mark 1 has a slightly higher and more homogeneous resolution. So, it scores better on a full frame camera, like the Canon 5D Mark II used in the review.
But, as we also added to the review, if you make the same comparison on a APS-C, it’s the Canon EF 70-200mm f/2.8L IS II USM that comes out slightly ahead. This may be the reason why the results are in other reviews made on other cameras.

So, what it means is that both lenses are really really close, and if you have a full frame it is better go for the older version and if you have an APS-C the newer version is a better choice.

Axel from DxO Labs


then you have tetsted  a bad copy of the lens

dpreview, Imaging-Resource, photozone  puts the new 70-200/2,8  ahead of the old one , tested on APS or 24x36mm
 
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macrobild
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« Reply #3 on: September 22, 2011, 09:07:23 PM »

Hi,



So, what it means is that both lenses are really really close, and if you have a full frame it is better go for the older version and if you have an APS-C the newer version is a better choice.

Axel from DxO Labs

nope, make no sence at all

re-test the lens, another copy of the 70-200/2,8is MK2
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PHOTOUK
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« Reply #4 on: September 23, 2011, 06:30:57 PM »

Well this is a turn-up for the books. Sad

I spent my hard earned money on a new lens which would appear to perform worse than the old according to the figures.

Unfortunately I have sold the original MkI lens and am not able to take any reference shots that might help to support or otherwise the DxoMark findings.

I wonder, was there only one lens used for the test or more?

This all seems to fly in the face of popular wisdom, and indeed is seriously depressing me Wink
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macrobild
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« Reply #5 on: September 23, 2011, 10:28:45 PM »

Well this is a turn-up for the books. Sad

I spent my hard earned money on a new lens which would appear to perform worse than the old according to the figures.

Unfortunately I have sold the original MkI lens and am not able to take any reference shots that might help to support or otherwise the DxoMark findings.

I wonder, was there only one lens used for the test or more?

This all seems to fly in the face of popular wisdom, and indeed is seriously depressing me Wink



I  have tested  lenses since 1978 and coauthored a number of tests in Sweden, 70-200/2, 8is mk2 has better resolution, especially when it comes to F 2.8 throughout the zoom range, the DXO  come up with that old Canon  70 - 200/2,8is  is better in terms of 24x36mm sensor  is a mystery, especially when the tests  of  Photozone, Image Review and Dpreview  shows another result My own  comparisons show that 70-200/2, 8is mk2 is clearly better than my old lens.
So I think it would be good if DXO tetade another copy of Canon's latest zoom lens that are among the best ever made
« Last Edit: September 23, 2011, 10:31:12 PM by macrobild » Logged
PHOTOUK
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« Reply #6 on: September 24, 2011, 09:07:43 PM »

Just for interest I did some tests today. Just some images of a watch taken with the following Canon EF Lenses set at f5.6 and 1.5M distance RAW. Usual tripod, mirror lockup, live focus and reasonable care, but not lab conditions.

85mm/f1.8
24-105/f4.0 IS
70-200mm/2.8 IS MKII

Doing a bit of unscientific pixel peeking on unmodified data the lenses came out as follows.

The 24-105 came out worse, low resolution compared to the other two.
The 85mm was difficult to separate from the 70-200 on resolution but to my eye was slightly worse. Contrast with the 85mm was certainly worse than the 70-200.
The 70-200 seems to me to be better than both the 24-105 and the 85mm. Contrast seems better and resolution seems better.

So I am happy with my choice of the 70-200 MKII.

I don't know what the DxO figures are telling me. In this respect the figures seem to be failing me as they are not reflecting what I can see in my own images.

Figures for resolution are affected by the sensor but I am using a Canon 5D MKII and according to DxO I should not be seeing better resolution with my 70-200 as compared to my 85mm.

There is something that needs clarifying here or there is a chance that the value  of the DxO figures will be degraded by these apparent anomalies.

For the record I am a Test and Measurement engineer of some 30+ Years standing. I do understand how difficult and complex these issues are but I cannot ignore what I see.


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John Daniel
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« Reply #7 on: September 25, 2011, 03:42:07 PM »

I do agree with the above photographers that DXO marks on the 70-200 f/2.8L IS II do not make sens at all.

I have had the 70-200 f/2.8L IS, the 70-200 f/4L IS which was superior in sharpness wide open the the 2.8L IS.

But the 70-200 f/2.8 L IS II is way superior in sharpness wide open or at f/8 to the 2 previous ones (F2.8L IS and f/4L IS), and a lot more responsive in low light. This is also confirm by 2 sources that I trust: Photozone.de and SLRGear.com

Maybe the DXO technology has some limits... or you really had a lemon in your hands.

JD
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Nicolas
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« Reply #8 on: September 26, 2011, 01:32:17 PM »

Hi,

We had a second look at our results and we can confirm that we didn't mix up the measurements.
We also had a closer look at the other measurements published on the websites you mentioned, and even if some graphs show some strange patterns, they seem to all agree on the better quality of the Mark II.
So, if there is a consensus that the Mark II is better than the Mark I, the only explanation would be that we measured a bad sample of the lens, even if it was brand new.
So, we will try to fit another sample of the Canon 70-200mm F/2,8 IS II in the lab schedule, as soon as we can get another sample.

Axel from DxO
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NoRulz
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« Reply #9 on: September 30, 2011, 10:47:31 AM »

When looking at the measurement data of the MkII the divergence between horizontal and vertical MTF is larger than for most other lenses (50/1.8, 85/1.8 and the MkI). Might this be related to the issue at hand? I believe to remember that this can be caused by a lens defect (de-centering?).
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