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Author Topic: DxO and Sony FE 28mm f/2  (Read 739 times)

sbay

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DxO and Sony FE 28mm f/2
« on: May 21, 2017, 04:00:48 PM »

I noticed a pretty big discrepancy in sharpness for DxO ratings on the 28mm f/2 lens depending on whether it was mounted on the A7R (36MP) or A7RII (42MP). It jumps from 24 to 35 P-MPix.

https://www.dxomark.com/Lenses/Compare/Side-by-side/Sony-FE-28mm-F2-on-Sony-A7R-versus-Sony-FE-28mm-F2-on-Sony-A7R-II__1516_917_1516_1035

Should I chalk this up to sample variation, measurement error, and/or recording error? Is this due to some weird scaling/normalization of their scores? The difference seems bigger than can be explained by the slightly higher res sensor in the a7RII.
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E.J. Peiker

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Re: DxO and Sony FE 28mm f/2
« Reply #1 on: May 21, 2017, 10:18:04 PM »

My guess would be that at least a big part of it is due to the fact that the a7R had a significant shutter shock issue with no electronic first curtain where the a7R2 largely got rid of that with both an EFC and a redesigned shutter to reduce shock.
« Last Edit: May 21, 2017, 10:24:03 PM by E.J. Peiker »
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sbay

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Re: DxO and Sony FE 28mm f/2
« Reply #2 on: May 22, 2017, 01:46:44 AM »

That makes sense. I had forgotten that the a7r did not have EFCS.

I went and looked at a bunch of other lenses on the a7r and a7r II. There was a consistent ~10 P-MPix difference in sharpness rating which would make sense if the EFCS is the issue.

sony 50 f/1.8  16 -> 26
sony 35 f/2.8  22 -> 32
sony 90 f/2.8  32 -> 42

sony 55 f/1.8  29 -> 40
sony 16-35 f/4 16 -> 26
sony 70-200 23 -> 35
sony 70-300 15 -> 24


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davidgp

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Re: DxO and Sony FE 28mm f/2
« Reply #3 on: May 22, 2017, 02:07:32 AM »

As far as I remember there is no normalization in DxO, the results are resolution dependent of the camera they are using... They explain that a bit here https://www.dxomark.com/Reviews/Looking-for-new-photo-gear-DxOMark-s-Perceptual-Megapixel-can-help-you where they introduce their perceptual megapixel sharpness measurement for lens.


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