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DxOmark: FE 100-400mm GM, compact and optically excellent
  
 
Brandon Dube
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p.3 #1 · p.3 #1 · DxOmark: FE 100-400mm GM, compact and optically excellent


virtualrain wrote:
This is still a bit confusing though... On one hand, you're saying your tests were accurate... on the other, you're saying Sony knows it's better. So is it better than you tested or not? If not, has Sony's view changed or you've just agreed to disagree on the results?


Translation: "We're better at testing than Sony. The lens should be better than it is, but the gap between as-designed and as-built is larger than typical for this lens. We like Sony, and aren't testing more 70-200s for them then the large quantity we already have and consider the discussion closed."

It's hard to disagree about raw data unless there is an error made gathering it, but we haven't made one. Whether Sony is happy that a relatively flagship lens for their system is worse than it could be is another matter.



Jul 31, 2017 at 06:40 PM
GMPhotography
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p.3 #2 · p.3 #2 · DxOmark: FE 100-400mm GM, compact and optically excellent


Real world after another 20k plus with the GM 70-200 it's not great at 200 I have to back off to 195 or so. Saleable images but my Batis 135 trounces it


Jul 31, 2017 at 07:10 PM
dgpfotografia
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p.3 #3 · p.3 #3 · DxOmark: FE 100-400mm GM, compact and optically excellent


RCicala wrote:
We are, we solved the 70-200mm mystery long ago. It wasn't a mystery, everything worked as it should, but I ended up testing 60 some copies before we really were comfortable with it because Sony understandably doesn't want to share their secret AF algorithms so we had to figure things out ourselves. The bottom line is our original tests were correct, I just wasn't comfortable with them because Sony kept insisting there must be a problem, they knew it was better than that.

I've started testing 100- 400s, but so far have just done a few and just at 100
...Show more

Many thanks Roger,

Yes, I trust your tests more than Sonys and although, I already discarded some time ago this lens, it is good to see that my intuition about it was right .

Waiting for your tests of 100-400 (I don't have money to buy it right now, and the 12-24 it is more interesting buying for me), and yes, clients pay food and clothes, so that takes precedence than making blog posts that we enjoy for free (in my case for free, I live in the other side of the Atlantic, so I cannot even be a client to lensrental).

Many thanks for the review... and more specially, your teardowns

David



Aug 01, 2017 at 01:49 PM
RCicala
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p.3 #4 · p.3 #4 · DxOmark: FE 100-400mm GM, compact and optically excellent


virtualrain wrote:
This is still a bit confusing though... On one hand, you're saying your tests were accurate... on the other, you're saying Sony knows it's better. So is it better than you tested or not? If not, has Sony's view changed or you've just agreed to disagree on the results?


We tested it, thought the results were accurate, but Sony insisted they couldn't be, they knew the lens was better than we showed.

Given that the lens had new technology, we were completely willing to consider our results might not be accurate and tried several suggestions from Sony, and several of our own ideas. Then we waited and repeated tests on later batches in case just the early ones had problems. Our results were always the same and as we investigated the lens more we found multiple reasons to be more comfortable with our results. They are valid and accurate.

There is still the possibility that the lens performs better close up than at infinity, but that always exists. But the Sony computer generated results that are way better than our real world tests are done at infinity. So a lot of time was spent confirming that the lens isn't as good in real life as Sony thought it was going to be.

Doing all this took many months. By the time we were done we figured not many people cared and we had lots of other things to do, so I never wrote up an official report. And there's the part that Sony fanboys are becoming the worst and writing a negative Sony article means hours and hours of responding to emails and comments.






Aug 02, 2017 at 01:02 PM
Parariss
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p.3 #5 · p.3 #5 · DxOmark: FE 100-400mm GM, compact and optically excellent




RCicala wrote:
We tested it, thought the results were accurate, but Sony insisted they couldn't be, they knew the lens was better than we showed.

Given that the lens had new technology, we were completely willing to consider our results might not be accurate and tried several suggestions from Sony, and several of our own ideas. Then we waited and repeated tests on later batches in case just the early ones had problems. Our results were always the same and as we investigated the lens more we found multiple reasons to be more comfortable with our results. They are valid and accurate.
...Show more

FWIW, Roger, a lot of us *do* care, and we're very grateful!



Aug 02, 2017 at 01:26 PM
conrad2nr
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p.3 #6 · p.3 #6 · DxOmark: FE 100-400mm GM, compact and optically excellent


Parariss wrote:
FWIW, Roger, a lot of us *do* care, and we're very grateful!


Same here, your reviews and opinions are greatly appreciated.



Aug 02, 2017 at 02:15 PM
 

Search in Used Dept. 



Fred Miranda
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p.3 #7 · p.3 #7 · DxOmark: FE 100-400mm GM, compact and optically excellent


Brandon Dube wrote:
Translation: "We're better at testing than Sony. The lens should be better than it is, but the gap between as-designed and as-built is larger than typical for this lens. We like Sony, and aren't testing more 70-200s for them then the large quantity we already have and consider the discussion closed."

It's hard to disagree about raw data unless there is an error made gathering it, but we haven't made one. Whether Sony is happy that a relatively flagship lens for their system is worse than it could be is another matter.


Brandon,
What I get from your answer is that in Sony's mind, their 70-200GM optical design yields superb results and that's what matters. In reality though, consumers are not seeing these results in real production lenses due to quality control and manufacturing tolerance which are responsible for lens variability...This is a shame and I hope it changes in the furure whenever we double resolution again.



Aug 02, 2017 at 02:31 PM
Fred Miranda
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p.3 #8 · p.3 #8 · DxOmark: FE 100-400mm GM, compact and optically excellent


RCicala wrote:
We are, we solved the 70-200mm mystery long ago. It wasn't a mystery, everything worked as it should, but I ended up testing 60 some copies before we really were comfortable with it because Sony understandably doesn't want to share their secret AF algorithms so we had to figure things out ourselves. The bottom line is our original tests were correct, I just wasn't comfortable with them because Sony kept insisting there must be a problem, they knew it was better than that.

I've started testing 100- 400s, but so far have just done a few and just at 100
...Show more

Although DXO posted their results and the 100-400GM did well with their methodology, many of us are waiting for your optical bench MTF graphs before jumping on this lens.
I find my own tests more compatible with your results than with DXO with many lenses.

My copy did well at infinity with great results. I'm not sure if it will have higher resolution and consistency when compared to the superb Canon EF 100-400L IS II but even if it's comparable, we have a winner.



Aug 02, 2017 at 02:37 PM
GMPhotography
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p.3 #9 · p.3 #9 · DxOmark: FE 100-400mm GM, compact and optically excellent


Fred Miranda wrote:
Brandon,
What I get from your answer is that in Sony's mind, their 70-200GM optical design yields superb results and that's what matters. In reality though, consumers are not seeing these results in real production lenses due to quality control and manufacturing tolerance which are responsible for lens variability...This is a shame and I hope it changes in the furure whenever we double resolution again.


I rent this lens often and I'm not totally pleased by it. I won't buy it thats for sure (70-200)



Aug 02, 2017 at 02:40 PM
Brandon Dube
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p.3 #10 · p.3 #10 · DxOmark: FE 100-400mm GM, compact and optically excellent


Fred Miranda wrote:
Brandon,
What I get from your answer is that in Sony's mind, their 70-200GM optical design yields superb results and that's what matters. In reality though, consumers are not seeing these results in real production lenses due to quality control and manufacturing tolerance which are responsible for lens variability...This is a shame and I hope it changes in the furure whenever we double resolution again.


I get to have multiple opinions, both as something of an expert on metrology, and also as a lens designer. I think the 70-200 GM has a flawed design for a telephoto zoom lens. Aspheres are not generally all that helpful in zoom lenses unless you put them very close to an entrance or exit pupil, or at the very front. The 70-200 GM has three(!) two of which have huge aspheric departures, all very close together, and some part of moving groups if memory serves.

As the beam walks around on the asphere during zoom, it will change from being the ideal shape to potentially a very bad shape. Obviously this is not notionally the case here, since the lens is very good as-designed. However, I suspect those aspheres are hellishly sensitive to misalignment.

The lens also has to orchestrate two focus motions, and there is no feedback circuit. There's a LUT in the lens, like any other, for the position of the USM motor to reach a given focusing distance. The PDAF/CDAF system spits out an estimate for the differential between where the lens thinks it is, and where the AF wants it to go. The microcontroller looks up this position in the LUT for large defocus, and goes there. As you near focus, the control may change from master-slave to a loop where the motor drives and they are looking to maximize some focus metric.

In this lens, the near focus control simply changes over to the second motor. If the USM motor is in the wrong place, the image quality will suffer and this is not correctable within their control loop. I think this is principally the issue with this lens, and why the IQ is not up to expectation.

The optical design and "system engnineering" (AF, IS, opto-mechanical links) contribute as much to variability as manufacturing tolerances and QC. It's really easy to design a lens that's great on paper, but very difficult to build because it is sensitive to misalignment. The real challenge is a high performance, insensitive design.



Aug 02, 2017 at 05:07 PM
virtualrain
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p.3 #11 · p.3 #11 · DxOmark: FE 100-400mm GM, compact and optically excellent


RCicala wrote:
We tested it, thought the results were accurate, but Sony insisted they couldn't be, they knew the lens was better than we showed.

Given that the lens had new technology, we were completely willing to consider our results might not be accurate and tried several suggestions from Sony, and several of our own ideas. Then we waited and repeated tests on later batches in case just the early ones had problems. Our results were always the same and as we investigated the lens more we found multiple reasons to be more comfortable with our results. They are valid and accurate.
...Show more

---------------------------------------------

Brandon Dube wrote:
I get to have multiple opinions, both as something of an expert on metrology, and also as a lens designer. I think the 70-200 GM has a flawed design for a telephoto zoom lens. Aspheres are not generally all that helpful in zoom lenses unless you put them very close to an entrance or exit pupil, or at the very front. The 70-200 GM has three(!) two of which have huge aspheric departures, all very close together, and some part of moving groups if memory serves.

As the beam walks around on the asphere during zoom, it will change
...Show more

Thank you both for sharing this... It all makes perfect sense. As others have said, we value your testing and analysis greatly.



Aug 03, 2017 at 12:54 AM
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