Home · Register · Software · Software · Join Upload & Sell

Moderated by: Fred Miranda
Username  

  New fredmiranda.com Mobile Site
  New Feature: SMS Notification alert
  New Feature: Buy & Sell Watchlist
  

FM Forums | Alternative Gear & Lenses | Join Upload & Sell

1       2      
3
       end
  

Archive 2016 · Milvus testing better than classic Zeiss on DXO
  
 
U.C.
Offline
• • •
Upload & Sell: Off
p.3 #1 · p.3 #1 · Milvus testing better than classic Zeiss on DXO


I did a side by side test on my 5D2:


Zeiss 21 f2.8 vs Sigma 20 f1.8 Centre by Universal Creations, on Flickr


Zeiss 21 f2.8 vs Sigma 20 f1.8 Corner by Universal Creations, on Flickr



Nov 09, 2016 at 07:16 AM
alundeb
Offline
• • • • •
Upload & Sell: On
p.3 #2 · p.3 #2 · Milvus testing better than classic Zeiss on DXO


U.C. wrote:
I did a side by side test on my 5D2:

https://c2.staticflickr.com/1/751/21498245489_59b18c6d5d_o.jpg
Zeiss 21 f2.8 vs Sigma 20 f1.8 Centre by Universal Creations, on Flickr

https://c1.staticflickr.com/6/5646/21497235248_90b0a84e80_o.jpg
Zeiss 21 f2.8 vs Sigma 20 f1.8 Corner by Universal Creations, on Flickr


Thanks for the test. It is perfect to illustrate what happens.

In your test subject, the finest detail is recorded on the sensor at about 30- 40 lp/mm. In terms of megapixels needed to resolve it, it amounts to about 5 MP. The test subject lacks detail fine enough to evaluate resolution. But it represents quite well the line frequency used in the DXO actuance maps.

In the DXO actuance profiles, the highest center (ish) values for both lenses are at f/5.6. I then assume that the P-MP score for both lenses at DXO is calclulated at aperture f/5.6, all other apertures are totally ignored for that score.

Now, if we look at the center crops for f/5.6. I magnified them to 300%, and it may be a surprise to you, the Sigma is actually sharper.

Lastly, at the the edge, the Sigma lens is sharp but has astigmatism. The mean (loss of) actuance is then half of that measured in the worst direction, if it is focused like in you test.

Given that the P-MP is center weighted, and calculated at only f/5.6, it is not surprising at all that the Sigma lens gets a higher P-MP score thatn the Zeiss lens.




Nov 09, 2016 at 08:09 AM
alundeb
Offline
• • • • •
Upload & Sell: On
p.3 #3 · p.3 #3 · Milvus testing better than classic Zeiss on DXO


Steve Spencer wrote:
Did you look at the acutance graphs? We are talking about a difference of less than 5%, which is well within what Lens Rentals finds with sample variation when they compare 10 lenses. The problem is DXO reporting of their scores which is silly and misleading. The two lenses here are not nearly as far apart as the scores make them look.


I looked at the MTF measured by Lens Rentals again, especially the sample variation for the MP 100/2 classic.

The best copy has 25% higher MTF at 50 lp/mm than the worst copy. If we square that to translate to MP resolution, we get 56% higher resolution.

The Milvus is measured by DXO to 48% higher resolution than the classic. (34 vs 23 P-MP)

The difference between what is measured by DXO for the Milvus and the Classic is within the sample variation for the Classic found by Lensrentals.



Nov 09, 2016 at 12:06 PM
Steve Spencer
Offline
• • • • • •
Upload & Sell: On
p.3 #4 · p.3 #4 · Milvus testing better than classic Zeiss on DXO


alundeb wrote:
I looked at the MTF measured by Lens Rentals again, especially the sample variation for the MP 100/2 classic.

The best copy has 25% higher MTF at 50 lp/mm than the worst copy. If we square that to translate to MP resolution, we get 56% higher resolution.

The Milvus is measured by DXO to 48% higher resolution than the classic. (34 vs 23 P-MP)

The difference between what is measured by DXO for the Milvus and the Classic is within the sample variation for the Classic found by Lensrentals.


Thanks for doing the math on that. As I suspected the "huge" difference are within sample variation. It is nice to see that Zeiss and others are tightening up their manufacturing tolerances, but we also need to be careful in reading too much into what look like differences in numbers.



Nov 09, 2016 at 02:44 PM
1       2      
3
       end






FM Forums | Alternative Gear & Lenses | Join Upload & Sell

1       2      
3
       end
    
 

You are not logged in. Login or Register

Username     Reset password