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karelderaat

I use the NEX system since 2012. Thus I am always interested in tests of the e-mount lenses meant for the APS-C sensor size. Just browsing Photozone I discovered the very different testing results of the SEL 1855 obtained with a NEX 5 and a Nex 7. In particular the sharpness results drew my attention.

 

How is it possible that the same lens has much higher MTF50 scores for the NEX 5 than for the NEX 7.

 

I cannot follow the explanation by Photozone for this discrepancy. According to the explanations provided by the company that developed the test program, as they can be reached via Photozone, a higher number of mega pixels on an identical surface area (sensor size) must theoretically result in at least the same MTF50 values. Unless:

  1. Not the same lenses were tested, which would mean substantial variation in quality and unacceptable quality-control practices by Sony; I cannot find info in the test as to whether these tests were indeed done with the same lens or with different lenses of the same type.
  2. There is something wrong with the sensor of the Nex 7 used; hardly probable.
  3. The signal processing by the NEX 7 does something that specifically affects the sharpness of pictures obtained with the SEL 1855; also hardly probable.
  4. One or both tests were really flawed.
In my opinion, the 4th option is the most likely one if the physically the same lens was tested. If not, the possibility of bad quality control by Sony might be an additional possibility. If this would be the only possibility, it becomes some sort of a gamble to buy Sony lenses.

I think, one of the testers will answer your questions. But PZ and most other test labs test only one sample of a lens. If you like to know about sample variance, I can recommend a visit on lensrentals blog: http://www.lensrentals.com/blog/2015/10/...ench-tests

karelderaat

Further to this. I do not understand why the SEL 18-55 is so negatively labeled as regards sharpness, while the standard zoom of the Nikon 1 system is deemed to be excellent to good. The MTF50 value over the whole sensor (picture) do not differ so much (it is the sharpness at equal print sizes that counts). Moreover, the user community (level and ambitions) will not differ very much between the Nex and the 1 system, so there is no reason to adapt the verdict to anticipated expectations of the users.

Sony's 24mp sensor (NEX 7 / A6000) suffers from edge smearing. I mentioned this a couple of times in various NEX7-based reviews ... so the results are not cross-comparable.

 

I don't remember for sure but I believe that this was actually the very same sample that we tested there.

 

As you may also observe in the NEX-5 vs NEX-7 reviews, the ratings are relative to the potential max LW/PH of the underlying test system.

Quote:I use the NEX system since 2012. Thus I am always interested in tests of the e-mount lenses meant for the APS-C sensor size. Just browsing Photozone I discovered the very different testing results of the SEL 1855 obtained with a NEX 5 and a Nex 7. In particular the sharpness results drew my attention.

 

How is it possible that the same lens has much higher MTF50 scores for the NEX 5 than for the NEX 7.

 

I cannot follow the explanation by Photozone for this discrepancy. According to the explanations provided by the company that developed the test program, as they can be reached via Photozone, a higher number of mega pixels on an identical surface area (sensor size) must theoretically result in at least the same MTF50 values. Unless:

  1. Not the same lenses were tested, which would mean substantial variation in quality and unacceptable quality-control practices by Sony; I cannot find info in the test as to whether these tests were indeed done with the same lens or with different lenses of the same type.
  2. There is something wrong with the sensor of the Nex 7 used; hardly probable.
  3. The signal processing by the NEX 7 does something that specifically affects the sharpness of pictures obtained with the SEL 1855; also hardly probable.
  4. One or both tests were really flawed.
In my opinion, the 4th option is the most likely one if the physically the same lens was tested. If not, the possibility of bad quality control by Sony might be an additional possibility. If this would be the only possibility, it becomes some sort of a gamble to buy Sony lenses.
  1. No idea what you are talking about. The test on the nex5 has lower resolution figures in the center than the nex7 test, consistently.
  2. the nex7 has a problematic sensor. Whether it has to do with the sensor glass or the micro lenses is not that important, it is known to have issues. That is why the border measurements show lower than expected resolution figures.
  3. The nex5 became the nex5r because of similar issues (corners with certain lenses would change in colour pretty drastically for instance). So it was not the 1st time Sony made this error.
  4. That leads to: the issue is not with the software used to measure, not with the lens, not with PZ. It is with Sony and their inconsistent sensor design concerning the nex-series.

karelderaat

So the conclusion would be that the lens is not that bad, but that the low score on the NEX 7 is a result of NEX 7 sensor issues. Good to know! Thanks. I have a 5R and a A6000. Do I have to expect the same issues with these cameras? 

Quote:So the conclusion would be that the lens is not that bad, but that the low score on the NEX 7 is a result of NEX 7 sensor issues. Good to know! Thanks. I have a 5R and a A6000. Do I have to expect the same issues with these cameras? 
No, the 5R has a good sensor. And I have not read much about issues with the A6000 (seems like Sony fixed the sensor issue with that model).
Quote:No, the 5R has a good sensor. And I have not read much about issues with the A6000 (seems like Sony fixed the sensor issue with that model).
 

The 16-70/4 was tested on the A6000 so ... no ...

karelderaat

Does that mean that you did the same comparison for the 16-70/4 (i.e., testing on two different cameras/sensors), or is the lens in this case the origin of less than satisfying test results?

Quote:Does that mean that you did the same comparison for the 16-70/4 (i.e., testing on two different cameras/sensors), or is the lens in this case the origin of less than satisfying test results?
 

The 16-70 was as soft on the A6000 as on the NEX7.

 

At some stage people complained that I should abandon the NEX7 so I bought the A6000.

I did some tests and there was no indication that something changed.

Some people claim that there's a difference but I reckon this is related to different focus settings.

Thus I sold the A6000 again because the viewfinder was worse.

FWIW, initially I even bought a 2nd NEX7 to verify the results but at no effect.

 

Maybe things have changed on the A6300 ... there's always another hope. ;-)

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