Is It Even POSSIBLE to get a properly aligned Sony A7R IV?
Related: digital sensor, focus skew, James K, lens mount, lens mount / sensor parallelism, quality control, Samuel Chia, Sony, Sony A7R, Sony A7R II, Sony A7R III, Sony A7R IV, Sony mirrorless
See Update on Sony A7R IV Lens Mount / Sensor Parallelism.
re: Sony A7R IV in for Repair of Lens Mount / Sensor Parallelism Problem
re: Lens Mount / Sensor Parallelism Afflicts All Brands
Is it even POSSIBLE to get a properly aligned Sony A7R IV?
Or any Sony camera? Or in general, most brands perhaps every brand?
Three years ago, I had a brand-new “swung” Nikon D850; see Nikon D850: Testing for a Misaligned Sensor.
This year, I am now pretty sure that the lenses were not the issue but a swung Hasselblad X1D.l see for example Alabama Hills Formations, Late Dusk, which shows a left/right skew, and this was true for several of the lenses, which is what leads me to think it was not the lenses, but a case of lens mount / sensor parallelism.
My concern is that Sony will return a still-defective camera to me. What has been nagging at me for months is that the the repaired Sony A7R IV was never really repaired in terms of lens mount / sensor parallelism. I now suspect that some subtle issues I saw were really the camera. But the more I learn from really knowledgeable people, the more I now conclude that “defective” is the norm, meaning a fault readily seen, but one that is deemed within specifications.
Poor lens mount / sensor parallelism can be distinguished from a problem lens by examining the entire edge of the frame near to far. If sharpness is observed (somewhere) on one side but not the other side (asymmetrical performance), that is not the fault of the camera, but rather an optical misalignment issue, which I lump under the term lens skew. Since both issues can be active, it can be tricky to evaluate.
I don’t know if Sony (or any other vendor) has the means to correct lens mount / sensor parallelism issues to within a rigorous tolerance (or at all), either in production or by repair.
To emphasize: this issue is not unique to Sony. The more I learn about it, the more I learn just how difficult it is to get a camera that does not have a significant amount of swing (left/right skew) and/or tilt (up/down skew) of the sensor versus the lens mount, a siuation I call lens mount / sensor parallelism.
Regrettably, I cannot share specifics I am aware of, but here is a good article on the subject.
“Tilt” is up/down and “swing” is left/right, but neither is quite correct terminology since the non-parellelism is a 3D thing. So I prefer to say “lens mount / sensor parallelism”. In my case, the issue seems to be swing (left/right parallelism), but with a 3:2 sensor aspect ratio, lack of parallelism is much less evident on the short dimension.
... Many lenses have their plane of focus tilted by at least 50 microns or more, some even over 200 microns. That won’t be invisible in your photos. Not even expensive lenses are free of this problem. I’ve yet to find a single copy myself that has a tilt of less than 10 microns
... Recently, I acquired a Sony a7R IV and naturally, I tested it to see if the sensor is straight. It was tilted by some 10-15 microns and swung by about 30. That makes 5 out of 5 bad Sonys, if you are still counting...
My Sony CMOS sensor at the bayer CFA surface appears to be warped. I say ‘appears’ because we did not have enough time to make sufficient measurements to properly verify this. I was told by the Keyence representative that wafers and CMOS sensors he has measured have all been warped. He thinks that the warping usually doesn’t exceed 10 microns for camera sensors...
...measurements also revealed that the sensor cover glass was not perfectly parallel to the light-sensitive plane of the sensor. You can forget about making accurate contact measurement off the front side of the sensor
See also The Great Flange-to-Sensor Distance Article. Part II: Photo Cameras.
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James K writes:
Years ago I was having an alignment problem with my Sinar eMotion 75 digital back. It had to be sent to Switzerland for repair. The Sinar factory was the only place that had a machine capable of measuring and adjusting the sensor in the back. Luckily it was under warranty. The cost to the dealer was around $900.
The result was perfect. Huge change. Gone were the unsharp areas. :)
DIGLLOYD: nice.
View cameras are pretty darn sloppy but at least they are easily shimmed, or the back itself.
