# DXO lens marks - have a laugh



## rfdesigner (Oct 10, 2015)

I was taking a brief glance at DXO looking at how lenses change between bodies with a view on the expected DXO marks for the 5Ds/r

I noticed something I thought sums up the DXO data in one very simple stat

http://www.dxomark.com/Lenses/Canon/Canon-EF-300mm-F28L-IS-II-USM-mounted-on-Canon-EOS-6D__836

yes you are reading that right.. they are rating the 300mmF2.8LII as having a sharpness of 21MPix.

on a 20.2Mpix camera.


There you go, Proof this lens is exceptional.. it actually increases the number of pixels in your camera!


----------



## ajfotofilmagem (Oct 10, 2015)

You know ... It's the magic of DXO. They can improve some equipment beyond the limits of the laws of physics, and can worsen others. :

Mathematics became an exoteric and mystical science. 8) ;D


----------



## AlanF (Oct 10, 2015)

This is actually very revealing about how DxO "measures" the Mpix rating. 

DxO clearly does not measure the Mpix data for each camera but calculates it from the measured camera-independent MTF of the lens. For the 1DX and 5DIII, the 300mm/2.8 II has a Mpix rating for each equal to the stated effective megapixels from the Canon datasheet - the lens is so damn sharp it outresolves the sensor. Unfortunately, the specs used by DxO for the 6D are the total 5568 x 3708 = 20.65 megapixels and not the 5472 x 3648 = 20.2 effective megapixels given by Canon. DxO has rounded up 20.65 to 21.

Thanks to your sharp eyes, we have learned about the short cuts taken by DxO - they calculate and don't measure lots of their results.


----------



## rs (Oct 10, 2015)

AlanF said:


> Thanks to your sharp eyes, we have learned about the short cuts taken by DxO - they *incorrectly* calculate and don't measure lots of their results.



There - I've amended your wording


----------



## Bdube (Oct 10, 2015)

AlanF said:


> This is actually very revealing about how DxO "measures" the Mpix rating.
> 
> DxO clearly does not measure the Mpix data for each camera but calculates it from the measured camera-independent MTF of the lens. For the 1DX and 5DIII, the 300mm/2.8 II has a Mpix rating for each equal to the stated effective megapixels from the Canon datasheet - the lens is so damn sharp it outresolves the sensor. Unfortunately, the specs used by DxO for the 6D are the total 5568 x 3708 = 20.65 megapixels and not the 5472 x 3648 = 20.2 effective megapixels given by Canon. DxO has rounded up 20.65 to 21.
> 
> Thanks to your sharp eyes, we have learned about the short cuts taken by DxO - they calculate and don't measure lots of their results.



Worth noting that they cannot extract "sensor independent" MTF - the can only take data from many sensors and make a guess. Because of the sampling in effect it will be highly inaccurate, but inaccuracy has never stopped DxO before.


----------



## AlanF (Oct 10, 2015)

How did you measure your Lensrental MTFs?


----------



## neuroanatomist (Oct 10, 2015)

AlanF said:


> How did you measure your Lensrental MTFs?



They use an optical bench, not a camera.


----------



## AlanF (Oct 10, 2015)

Which leads me on to the next question: does DxO use an optical bench?


----------



## neuroanatomist (Oct 10, 2015)

AlanF said:


> Which leads me on to the next question: does DxO use an optical bench?



No.


----------



## AlanF (Oct 10, 2015)

Like you, I don't take their testing very seriously, but have liked DxO Optics because of DxO PRIME noise reduction. DxO updated DxO Optics Pro today so it is compatible with the G3 X. I was looking forward to it for teasing some extra signal to noise but it is very disappointing. DPP 4 does a far, far better job of removing CA etc from RAW, and the out of camera jpegs are very well corrected.


----------



## AlanF (Oct 10, 2015)

The absurdity raised by the OP is not a statistical artefact but a silly mistake of plugging in the wrong sensor size into a calculation. They seem to have taken their eyes off the ball by going overboard on DxO One.


----------



## Don Haines (Oct 11, 2015)

AlanF said:


> The absurdity raised by the OP is not a statistical artefact but a silly mistake of plugging in the wrong sensor size into a calculation. They seem to have taken their eyes off the ball by going overboard on DxO One.



Don't knock DXO! I like them! Without DXO I would not have known that the plastic 50F1.8 that I paid $50 for (used) is a better lens that the 600F4 that other members of this form paid $12,000 for. Imagine, a better lens for only 1/240th the price......


----------



## neuroanatomist (Oct 11, 2015)

Don Haines said:


> Without DXO I would not have known that the plastic 50F1.8 that I paid $50 for (used) is a better lens that the 600F4 that other members of this form paid $12,000 for. Imagine, a better lens for only 1/240th the price......



Don't be absurd, it's entirely dependent on the use case. For example, consider the MOAI Score, where the 600/4 scores a 17 and the 50/1.8 scores a 3. If you were marooned on an island, with the 600/4 you could use the front element to start a fire each night, the hood as a seat, the lens cap as a bowl, and the barrel to crack open coconuts and fend off inimical wildlife. The 50/1.8 is so light it could not even be used to knock a coconut from a tree.


----------



## TeT (Oct 11, 2015)

AlanF said:


> The absurdity raised by the OP is not a statistical artefact but a silly mistake of plugging in the wrong sensor size into a calculation. They seem to have taken their eyes off the ball by going overboard on DxO One.



Sure it is absurd, BUT so is DxO


----------



## ejenner (Oct 11, 2015)

neuroanatomist said:


> Don Haines said:
> 
> 
> > Without DXO I would not have known that the plastic 50F1.8 that I paid $50 for (used) is a better lens that the 600F4 that other members of this form paid $12,000 for. Imagine, a better lens for only 1/240th the price......
> ...



Also, don't forget the HTMF (Hit The M*** F***) score. You can knock out that annoying wannabe photog next to you with the 600, but the 50 will just bounce of his head.


----------



## Ozarker (Nov 2, 2015)

neuroanatomist said:


> Don Haines said:
> 
> 
> > Without DXO I would not have known that the plastic 50F1.8 that I paid $50 for (used) is a better lens that the 600F4 that other members of this form paid $12,000 for. Imagine, a better lens for only 1/240th the price......
> ...


Thanks Neuro! Not only have you been a fountain of photography knowledge for me, but you even add to my $3 word collection sometimes. "Inimical" I like that one. Thanks again!


----------



## Don Haines (Nov 2, 2015)

neuroanatomist said:


> Don Haines said:
> 
> 
> > Without DXO I would not have known that the plastic 50F1.8 that I paid $50 for (used) is a better lens that the 600F4 that other members of this form paid $12,000 for. Imagine, a better lens for only 1/240th the price......
> ...


I'm lost here..... How do you use a lens element to start a fire at night...... I can see it working in the day when the sun is shining, but by moonlight?


----------



## AlanF (Nov 2, 2015)

Don Haines said:


> neuroanatomist said:
> 
> 
> > Don Haines said:
> ...



You have been trying three weeks? That's right, you can't do it at night. So, you can put the front element back and start taking photos again at 600mm.


----------

