Planar 80mm f/2.8 separation- opinions of effect?

[Dan Daniel]

Just ran across a Rolleiflex 2.8E with the 80mm Planar. And noticed the separation. Sort of a ring of rainbow-ish effect maybe -1/3 in diameter wise? Thoughts on how this might effect images? I am planning to test soon but ...

And I really yanked the image curve around in Photoshop to make the separation stand out in the first two shots. The 'plain' shot is no processing to give an idea of its 'natural' look.

 

[ic-racer]

Depending on why one wants a 2.8 lens. One school of thought is that an advanced design (like Planar) provides the best possible wide-open performance. In that case the wide-open performance will be compromised by the edge separation.

The other school of thought is that for the best absolute lens performance, one would be stopping down to about f11. In that case (as demonstrated in the ray trace below) the effects of lens damage at the perimeter of the glued elements is minimized or even totally avoided.

Image below is a Tessar with its single glued pair, not Planar, but the principle is the same.

 

[Dan Fromm]

Hmm. Since the lens is pre-WWII and uncoated, parasitic light from internal reflections will probably be a larger problem.

 

[Mark J]

It's quite localised. Is it aligned towards a corner of the frame ? ( those rays come through closer to the lens edge )
if not, you might get away with no effect. Otherwise it'll have a slight effect at the wider apertures.

 

[Dan Daniel]

Hmm. Since the lens is pre-WWII and uncoated, parasitic light from internal reflections will probably be a larger problem.

Actually, this is from about 1956 and is coated.

 

[OAPOli]

The rainbow pattern indicates a minute air gap in the cemented pair. E.g. tf you see purple, the gap is the size of the green wavelength (~500nm). Red and blue are reflected on the two new surfaces between the air gap (making purple) while the green reflections are removed via interference.

In general I think separation doesn't affect sharpness due to the gap being too small. But I think there will be more internal reflections leading to flare. This can be mitigated by stopping down when the separation is at the periphery.

 

[blee1996]

I don't have any medium format lens that has separation issue, but a few in 35mm format. For example, Zeiss Contarex 85/2, Voigtlander Septon 50/2. Both have about 1/3 to 1/2 of total diameter in some kind of edge separation. Lens separation seems to be quite common for lenses of that era.

In my limited experience, I do not encounter sharpness/resolution or even flare problem. I did use proper (square) lens hood for both. I often shoot the lens wide open, but not directly into sun. Some backlit subjects turned out just fine.

 

[campy51]

I bought the same camera with a little separation and it seemed fine to me, but there is a member (Nodda Duma) here that re-cemented it for me at a reasonable price and it came out nice. I just recently sold it when I bought my 3.5F and after about 2 years it looked great. I don't know if he's still doing it or what he charges now but it might be worth sending him a message.

 

[Dan Fromm]

Actually, this is from about 1956 and is coated.

Thanks for the correction. I should have twigged to "Carl Zeiss" without Jena and the focal length in mm not cm.