Helpful Posts: Hi Folks,
Just wondering if anybody has come across this defect in a lens. The lens is a Mamiya 127mm for a Mamiya RB67 Pro SD Camera.
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26th March 2018, 10:26 AM #1
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- Pat
Rainbow like pattern in the rear group.
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26th March 2018, 01:38 PM #2Moderator
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- Manfred Mueller
Re: Rainbow like pattern in the rear group.
Not a defect at all, but rather thin film interference patterns that are created by the anti-reflection coating on lens elements.
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26th March 2018, 01:47 PM #3
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Re: Rainbow like pattern in the rear group.
Hello Manfred, thank you for that, would this have any effect on the exposed film,
Pat.
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26th March 2018, 01:55 PM #4Moderator
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- Manfred Mueller
Re: Rainbow like pattern in the rear group.
No, while it looks strange to you, it's an outcome of the lens materials selected by the lens manufacturer.
I suspect the issue is only that obvious when you look at the back of the lens at an acute angle and disappears when you look straight down the optical axis. The coating reduces internal reflections of light, giving you a sharper image than the lens could deliver without it.
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26th March 2018, 02:16 PM #5
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Re: Rainbow like pattern in the rear group.
Thanks for that,
Best Wishes, Pat.
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