[Brightcolours]

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.