Can Pentax make A Decent Lens? Ricoh have not fixed QC issues...

Started 3 months ago | Discussions thread
BobORama
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Re: Can Pentax make A Decent Lens? Ricoh have not fixed QC issues...
In reply to Trevor G, 3 months ago

Trevor G wrote:

Perhaps I have no idea what you are getting at, in which case I apologise in advance. Post the full image so we can get some context.

If you want a real test, shoot a completely flat surface perfectly perpendicular to the normal. Or better, shoot a star field wide open. Focus the center of the image perfectly. You will see various aberations, but they should be equal in magnitude as you get farther from the center. Any decentering will be apparent.

Star test will also reveal this issue IN the center of the image if you defocus. Find a bright star ( must be a star, not Venus ), position it in the center of the frame, then defocus till you have a large disk still visible. It should be a circle, or look like your aperture blades. IF there is actual decentering of any element, it will cause the OOF image disk to have all manner of bad structure, and not be symmetric.

Also if 19 of your 20 lenses have this issue, perhaps the issue is with the camera body.

Do all of the lenes have a right - left focus shift?   And with a top to bottom shift?

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