# DXO does it again



## ahsanford (Feb 19, 2016)

They keep finding the inspiration to punish identical lenses for sensor stack reasons:

http://www.dxomark.com/Lenses/Sigma/Sigma-50mm-F14-DG-HSM-A-Canon-mounted-on-Canon-EOS-5DS-R__1009

http://www.dxomark.com/Lenses/Sigma/Sigma-50mm-F14-DG-HSM-A-Nikon-mounted-on-Nikon-D810__963

And the corresponding writeup is simply gold:
http://www.dxomark.com/Reviews/Sigma-50mm-F1.4-DG-HSM-Art-Nikon-mount-review-The-standard

It is comprehensively outresolved by a 5DS R, yet,* to DXO*, they can only describe the Nikon version as:

"The Standard"

"Outstanding peak sharpness"

[Masterpiece kiss to fingers gesture.]

- A


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## 3kramd5 (Feb 19, 2016)

Interesting that the chromatic aberration numbers are do different. I would have assumed it's the same lens with a different back end (F and EF have the same flange distance right?). Does that point to something non-repeatable in their test setup?


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## ahsanford (Feb 19, 2016)

3kramd5 said:


> Interesting that the chromatic aberration numbers are do different. I would have assumed it's the same lens with a different back end (F and EF have the same flange distance right?). Does that point to something non-repeatable in their test setup?



Stop using logic, silly. They said it is "The Standard". Why are we still shooting Canon after that's been settled? _*DXO has spoken!*_

#resolvingpowerisso2014 #dxo #fairandbalanced

- A


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## Sporgon (Feb 19, 2016)

3kramd5 said:


> Interesting that the chromatic aberration numbers are do different. I would have assumed it's the same lens with a different back end (F and EF have the same flange distance right?). Does that point to something non-repeatable in their test setup?



I think the flange distance on the EF is fractionally less than the Nikon F.

What I do find surprising is that the vignetting is -1.7 on the 5Ds and yet still -1.5 on the 5D. Now I'd have thought that the vignetting on the 5Ds was greater due to the much smaller pixel pitch, but looking at the small difference between the two cameras this can't be the case. Then you have the D810 at -1.2. Odd.


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## privatebydesign (Feb 19, 2016)

Sporgon said:


> I think the flange distance on the EF is fractionally less than the Nikon F.



You are right, 44.00mm vs 46.50mm.


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## JMZawodny (Feb 19, 2016)

The real question that needs to be asked and answered is "Who Cares?"


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## applecider (Feb 19, 2016)

Just to be sure didn't the 5dsr outscore the nikon in your links in every category and then got a lower score. Is that the correct reading, and their correct scoring?


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## neuroanatomist (Feb 19, 2016)

applecider said:


> Just to be sure didn't the 5dsr outscore the nikon in your links in every category and then got a lower score. Is that the correct reading, and their correct scoring?



Yes, it's all correct and makes perfect sense once you understand that the three factors of primary importance in DxO's Lens Score are:

1) the base ISO DR of the sensor behind the lens,
2) the base ISO color depth of the sensor behind the lens, and
3) the transmission score (T-stop) of the lens. 

Now, that makes perfect sense, right? :


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## bdunbar79 (Feb 19, 2016)

neuroanatomist said:


> applecider said:
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> 
> > Just to be sure didn't the 5dsr outscore the nikon in your links in every category and then got a lower score. Is that the correct reading, and their correct scoring?
> ...



Wait. Lenses don't have DR or color depth?


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## Don Haines (Feb 19, 2016)

bdunbar79 said:


> neuroanatomist said:
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> > applecider said:
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BINGO! That contestant wins a prize!


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## madmailman (Feb 19, 2016)

The best lens reviews money can buy and I'm sure Nikon pays handsomely.


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## Sporgon (Feb 19, 2016)

privatebydesign said:


> Sporgon said:
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> > I think the flange distance on the EF is fractionally less than the Nikon F.
> ...



Interesting. I was basing my comment on the fact that I use a couple of Nikkor lenses on the Canon and the adapter seems to protrude a mil or so and I get correct infinity.


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## 3kramd5 (Feb 19, 2016)

dilbert said:


> it is wrong to say that DxO's measurements/methods/results are wrong.



It's not wrong, however, to question whether they're right.


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## Refurb7 (Feb 26, 2016)

bdunbar79 said:


> neuroanatomist said:
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> > applecider said:
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It's all clear now. So the official DxO Score for lenses is actually THAT stupid. Now that is pretty stupid. Like pretty high up on the stupid scale. Maybe even off the scale. Like stupid on wheels. Or stupid with a jet pack. Or stupid with a cherry on top. Epic stupid with a fringe on top. They should get a prize for that.

The Nikon mount on this Sigma lens makes it 1 DxO point "better" than the Canon mount. Hahaha. Ha.


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## 3kramd5 (Feb 27, 2016)

privatebydesign said:


> Sporgon said:
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> > I think the flange distance on the EF is fractionally less than the Nikon F.
> ...



Is that enough to change the optical design, or does it merely frame slightly longer on the nikon?


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## Zeidora (Feb 27, 2016)

DXO measures "lens-PLUS-sensor-system" not lens alone. Accordingly, it makes perfect sense that the same lens gets different scores on different bodies from different manufacturers. Whether one agrees with this approach or not, they are very clear in what they try to measure. 

You can quibble with how the metric is achieved, but don't be surprised by the results. The repeated similar conclusion with different lenses on same bodies at least shows that they are consistent. I really don't understand why people here are so upset with it.


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## zim (Feb 27, 2016)

I wouldn't worry about it even DxO don't understand their results but at least they redefined the standard! ;D

"Mounted on the 50-Mpix Canon EOS 5Ds R, the Tamron SP 45mm F1.8 Di VC USD (Model F013) Canon is an excellent performer. It achieved a DxO Mark lens score of 36 points and a peak sharpness of 26 P-Mpix (at the optimal aperture). This a little lower than the 35mm f/1.8 model when mounted on the Nikon D810 — *a somewhat surprising result, given the Canon sensor’s higher pixel count*, "

http://www.dxomark.com/Reviews/Tamron-SP-45mm-F1.8-Di-VC-USD-Model-F013-Canon-Redefining-the-standard/Measurements-Good-score-good-sharpness-levels


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## StudentOfLight (Feb 27, 2016)

Zeidora said:


> DXO measures "lens-PLUS-sensor-system" not lens alone. Accordingly, it makes perfect sense that the same lens gets different scores on different bodies from different manufacturers. Whether one agrees with this approach or not, they are very clear in what they try to measure.
> 
> You can quibble with how the metric is achieved, but don't be surprised by the results. The repeated similar conclusion with different lenses on same bodies at least shows that they are consistent. I really don't understand why people here are so upset with it.


They could rectify the situation by applying the same algorithm to a good light scenario, thereby giving both a "good light" score and a "low-light score" which is derived from actually bumping up ISO as required and not amplifying ISO 100 in post. 

There can be a difference between ISO-3200 and ISO-100 pushed 5 stops:


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## Refurb7 (Feb 29, 2016)

Zeidora said:


> DXO measures "lens-PLUS-sensor-system" not lens alone. Accordingly, it makes perfect sense that the same lens gets different scores on different bodies from different manufacturers. Whether one agrees with this approach or not, they are very clear in what they try to measure.
> 
> You can quibble with how the metric is achieved, but don't be surprised by the results. The repeated similar conclusion with different lenses on same bodies at least shows that they are consistent. I really don't understand why people here are so upset with it.



How does it make sense for the same lens to score higher on a 36mp Nikon D810 than on a 50mp Canon 5DSR? Because they've rigged their system to give that result maybe?


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## 3kramd5 (Feb 29, 2016)

dilbert said:


> 3kramd5 said:
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What I'm asking, though, is whether the sigma/zeiss/tamron/tokina/whoever lenses for EF vs F are different anywhere other than the back end.

If one were able to control the position of a camera such that you could take two pictures behind F and EF mount versions of the same lens with the sensors in the exact same physical location and orientation, would the pictures be identical excepting any potential crop from the horizontal dimension of the nikon FX sensor being slightly shorter than that of the canon full frame sensor? Or would one have a tighter crop than the other for optical reasons (lens further from sensor)?

I've always assumed that the designs were basically modular, where the manufacturer can put whatever back end (i.e. mount) on they need to based on assumed demands, but am wondering how a different flange distance may affect that.


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## privatebydesign (Mar 1, 2016)

3kramd5 said:


> dilbert said:
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Dilbert is 100% wrong.

The same lens in different mounts will pass the light to the different sensors at the same angle, the length of the mount is irrelevant, it is the distance from the rear element to the sensor that is important and will be consistent across different mount versions of the same lens.

The only situation where it might be different, and it would make no commercial sense to do it, was if the rear element was in different places for each version, but this would require different element spacing and optical formulas for each version and would have no real benefit.


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## 3kramd5 (Mar 1, 2016)

And the mount handles the positioning. Makes sense


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## Diko (Mar 21, 2016)

neuroanatomist said:


> 3) the transmission score (T-stop) of the lens.


 What is that?


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## neuroanatomist (Mar 21, 2016)

Diko said:


> neuroanatomist said:
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> > 3) the transmission score (T-stop) of the lens.
> ...



Well, depending on context a T-stop is either a) the measured amount of light passing through a lens (vs. f-stop, which is calculated based on focal length and iris diaphragm diameter) or b) a station in Boston's subway system, which is called the T.


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## Sporgon (Mar 21, 2016)

neuroanatomist said:


> Diko said:
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Ah-ha ! I get it now. DxO set their lighting from the T stop. That explains a lot - but I thought they were French.


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## neuroanatomist (Mar 21, 2016)

Sporgon said:


> neuroanatomist said:
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Hey, be nice. They're actually rebuilding a bunch of the stations with lots of exterior glass, in fact the Government Center station just reopened today:







That's way too much light for a proper DxO test. They could use the tunnels, though.


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## j-nord (Apr 16, 2016)

If you dig into DXO metrics they are very useful for comparison but if you compare their overall scores or read the reviews you are absolutely wasting your time. Nikon gets what they pay for with the overall scores and review headlines


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