Is this lens balsam seperation?

[pavost]

This lens came with a second hand Mamiya rb67 I got off the bay. Seems to have some kind of separation on around 15% of the rear element.
Will this affect image quality? The lens is a 127mm 3.8 sekor C if that makes any difference.

Thanks

 

[Highway 61]

This is indeed separation. It may or may not affect image quality under some lighting conditions (less contrast and more flare). Only field tests will tell.

It's a long focal length thus the effects of separation at the rear element will be less annoying than with a short focal length.

 

[rick oleson]

Looks like. Usually (almost always), you will see the separated area as being highly reflective, and generally with a rainbow pattern of colors at the edge where it's beginning to separate. The main effect of separation is that reflectivity - without the cement, and with no AR coating on the cemented surfaces, about 8% of the light that strikes that part of the lens is bouncing back. This will lead to increased flare, and you might see some odd flare patterns in bright light. It should not, though, have a visible effect on sharpness, and you can get good results from it if you keep it out of direct light. It has a big effect on the resale value, though.... :\=