# RF 50mm f/1.2L on DxOMark: How to decipher?



## YuengLinger (Jun 15, 2019)

Canon RF 50mm f/1.2L USM review - DXOMARK


Canon announced the RF 50mm f/1.2L USM at the same time as the EOS R, its first full-frame mirrorless camera. Consequently, it has the Canon RF lens mount that has a diameter of 54mm and a flange depth of 20mm. As part of Canon’s L series, it is designed for professional photographers who want a...




www.dxomark.com





If anyone can explain what this means in the context of other reviews, I'd appreciate the insights! For example, opiticallimits (nee photozone) is practically breathless:





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Canon RF 50mm f/1.2 USM L - Review / Test Report


Canon RF 50mm f/1.2 USM L - Review / Test Report




www.opticallimits.com





DxOMark...Is the reviewer just being coldly clinical to convey objectivity? Because it seems she sees it as nothing special, just incrementally better than the ef 50mm f/1.2L.

If all you want to do is bash DxOMark _generally_, without any explanations regarding this specific review, please save your time and ours. If you own this lens and have true insights, or you think you understand why the results line up the way they do because of testing methodology (or lack of), please chime in!

Thanks!


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## koenkooi (Jun 15, 2019)

I seem to recall that the DxO score has a factor for the performance when completely stopped down, which is why Canon lenses that go down to f/32 get a lower score than lenses to only go down to f/16 or f/22. Compare the 50mm f/1.8 with the 600mm F/4L II.


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## Pape (Jun 15, 2019)

i wonder how they acquire copys they test? do they buy like all others or ask companys send one for test?
What i understanded they choose aperture what gives best shaprness ,and lens errors they put worst value or fully open value.
but i am not good to understand complex technical text 
https://www.dxomark.com/dxomark-lens-camera-sensor-testing-protocol/


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## neuroanatomist (Jun 15, 2019)

Honestly, a general bash of DxO is the answer to this specific review as well. DxO’s _lens_ scores aren’t. They are lens+sensor scores. All the higher-scoring 50mm lenses are on higher resolution sensors than the EOS R. Not a coincidence.


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## Pape (Jun 15, 2019)

That might be true when watching what score 50mm sigma got with 5div its just 39score ,point more than RF50


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## Antono Refa (Jun 15, 2019)

koenkooi said:


> I seem to recall that the DxO score has a factor for the performance when completely stopped down, which is why Canon lenses that go down to f/32 get a lower score than lenses to only go down to f/16 or f/22. Compare the 50mm f/1.8 with the 600mm F/4L II.



IIRC, the claim was DxO averages performance for all aperture values, so lenses that go to f/32 get lower scores than lenses than go only to f/22. Same goes for wider apertures - the 16-35mm f/2.8L mk III isn't that far from the f/4L at equivalent apertures.


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## Viggo (Jun 15, 2019)

Antono Refa said:


> IIRC, the claim was DxO averages performance for all aperture values, so lenses that go to f/32 get lower scores than lenses than go only to f/22. Same goes for wider apertures - the 16-35mm f/2.8L mk III isn't that far from the f/4L at equivalent apertures.


Shouldn’t that play in favor of the RF50 that “only” goes to f16.


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## Del Paso (Jun 15, 2019)

Sorry, but I think DXO testing isn't even worth a single comment.
We all know the RF 1,2/50 is a fantastic lens, so, why care about DXO ratings?


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## Neutral (Jun 15, 2019)

What is interesting are real measurements results and not lens scores.
1. F-stops vs T-stops:
Canon RF 50mm F/1.2 has only 1.5 T-stops while competing Sony 50mm F1.4 has 1.6 T-stops, which means Canonn has higher optical losses and as result there is almost no benefit in shooting low light using Canon RF 50mm f/1.2 compared to Sony 50mm f1.4. DOF is different subject.
Sony 85 f1.4 GM has the same 1.5 T- stops as Canon RF 50mm f/1.2
T-stops/F-stop ratio is what is really matters when talking about lens light transmission optical efficiency.
Canon 1.2/1.5=0.8, Sony 1.4/1.6=0.875. Very interesting.
I was expecting RF lenses to have higher optical efficiency considering all claims that wider mount diameter results in better lense optical efficiency.
2. For lens resolution efficiency (when tested on camera body) absolute resulting resolution is not relevant and does not matter as it all depends on camera sensor resolution.
Important is the overall system resolution efficiency ratio = Measured_resolution/camera_sensor_resolution
In other words how much lens deteriorate overall system resolution.
Results for RF 50mm f/1.2 are bit strange for me.
For Canon RF system efficiency is 22/30.3=0.67 ( on EOS-R) whereas for sony it is 41/42=0.976 (50mm f1.4 on a7r2)
Where are here claimed benefits of Canon RF mount system over Sony E-mount system ?
After so many discussions regarding RF mount and RF mount lenses benefits over competing systems I was expecting opposite results, a bit above Sony system, at least 0.93-0.95 whould be something good.
Maybe RF lenses are optimized for future Canon sensors for new RF bodies on their roadmap rather than for old sensor from EF mount used in EOS-R which has microlens design optimized for EF mount ?





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Canon RF 50mm f/1.2L USM on Canon EOS R vs Sony FE 85mm F1.4 GM on Sony A7R II vs Sony Carl Zeiss Planar T* FE 50mm 1.4 ZA on Sony A7R II







www.dxomark.com


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## YuengLinger (Jun 15, 2019)

Del Paso said:


> Sorry, but I think DXO testing isn't even worth a single comment.
> We all know the RF 1,2/50 is a fantastic lens, so, why care about DXO ratings?


Do you own the lens? Still not a lot of especially helpful sample shots easily found on web.


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