Off coplanar projection - Printable Version +- Opticallimits (https://forum.opticallimits.com) +-- Forum: Forums (https://forum.opticallimits.com/forumdisplay.php?fid=4) +--- Forum: Just Talk (https://forum.opticallimits.com/forumdisplay.php?fid=17) +--- Thread: Off coplanar projection (/showthread.php?tid=1525) |
Off coplanar projection - Guest - 04-12-2014 Hello What is an off coplanar projection defect ? I read in the Zone of photozone that it was a form of centering defect. What is the symptom and what is the cause of such defect ? Do all decentered lens suffer from off-coplanar projection ? There is a test that mention such defect but there is no image sample showing the issue: http://www.opticallimits.com/Reviews/276-tokina-af-28-70mm-f28-26-at-x-pro-ii-lab-test-report--review?start=1 Best regards Emmanuel Off coplanar projection - Rainer - 04-12-2014 If you imagine a very simple optical system, that just uses 2 lenses, and if you also assume, the first lens of the two lenses would be in the "correct position" (whatever that actually means), then you will find several ways, in which the seconds lens can be out of its "correct position". Typically, to be correct, the lenses have to be "coplanar" and "coaxial" ... this means the two planes in which the lenses are have to be parallel and the lenses shall be in the same optical axis. If the planes are not parallel, the resulting image defect is different from that when the lenses are not in the same axis. The cause? Whichever you want! It might already be a defect that has its origin in the assembly process. The lens might have been faling down or it took a hit when it was used. Note, however, that no lens is the world is absolutely perfectly centered. Just my 2cts ... Rainer Off coplanar projection - dave9t5 - 04-13-2014 Quote:Hello RTFAQ: http://www.opticallimits.com/lens-test-faq Q: What is a <i>centering</i> defect ? <p style="margin-left:40px;">A: A centering defect originates in a misaligned lens element or lens group. The result is a blurry corner, an off-coplanar projection (symmetrical blur) or object edge shadows. A centering defect is normal to some degree - there's simply no perfect lens out there, not even a Leica. Generally centering problems are more obvious with large aperture lenses and they're more frequent with budget (third-party) lenses. |