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A-Mount Ultrawides

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sybersitizen View Drop Down
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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 09 February 2019 at 17:41
Originally posted by QuietOC QuietOC wrote:

Originally posted by addy landzaat addy landzaat wrote:

You can find them onOptical Limits . But here you go:

Sony/Minolta./Tamron 11-18
11mm: - 2.69%
14mm: - 1.63% (1.66% Sony)
18mm: - 0.883% (0.924% Sony)

I am surprised by the difference between the Tamron (on Canon) and the Sony. Probably sample variations?

Maybe that is why Sony never added in-body Lens Compensations for the 11-18. I have seen premade lens profiles make images worse.

I see no logical reason for Sony leaving out correction for the 11-18mm, and no geometric correction tools I've used have made images worse.

I have PTLens, which allows me to look at and compare the geometric correction characteristics of hundreds of lenses.

The program lists two Sigma 10-20mm lenses (as does the dyxum lens database): an f/4-5.6 EX DC and a newer f/3.5 EX DC HSM.

All three need considerable correction that varies at different focal lengths. The Tamron/KM/Sony and the newer Sigma need only slight correction at 18mm, but a lot at 11mm. The older Sigma is the opposite. In no case is FOV significantly impacted.

Here are the results when the PTLens corrections are applied to a uniform grid. Where the grid shows pincushion distortion, it means the lens has barrel distortion... and vice-versa. I designated the A77 as the camera, though it should be the same with any supported APS-C camera.



PTLens doesn't do automatic CA correction, so that can't be compared.
 



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