The BEST way to solve lens separation

**ic-racer** · 14-Jan-2012, 09:57

I have read all the posts and articles on lens separation that I could find on the internet. The following is the best method I could find for my lens.

The lens is a modern, multicoated lens. Likely with modern UV cured cement that has come apart around the edges. both the front cell group and rear cell group have a "Free Centered" optical element. That is, the element are glued together WITHOUT being held in place by the lens body. In fact the inner most elements (closest to the shutter) do not touch the lens housing at all, there is an air gap all the way around the perimeter of the glass. Virtually impossible to center correctly at home.

**ic-racer** · 14-Jan-2012, 09:59

The lens is a 90mm Horseman lens. The issue is that this is the only f5.6 90mm lens that fits through the hole in the Horseman FA.

Here is the lens. I don't have a good image of the separation but it is severe, and easy to see. BTW, the lens takes near perfect images. It was only after the "repair" that I notice the separated elements produced a slightly less sharp image in one corner, likely do to some focus shift and less than ideal field flattness.

**E. von Hoegh** · 14-Jan-2012, 10:00

Kind of like an Angulon.... machine a jig to center things.

**ic-racer** · 14-Jan-2012, 10:01

What is the key to this repair?

Replacing the elements with new ones from another lens!

Why?

It turns out the CALTAR HR 90mm lens has the exact same lens elements. But the rear housing is NOT the same as the HORSEMAN 90mm rear housing. The HORSEMAN branded rear lens housing has a removable collar that reduces the diameter just enough to get the lens through the hole in the lensboard, without having to remove the rear element and screw it in from behind the bellows.

**ic-racer** · 14-Jan-2012, 10:02

So, in this 'lens separation repair' I merely swapped all the glass from one lens housing to the other.

**ic-racer** · 14-Jan-2012, 10:06

What cost was involved?

I paid $90 for a cosmetically nice Horseman 90mm lens with severe separation and $275 for a CALTAR HR 90mm with pristine glass. After the swap I sold the CALTAR with separation (and near mint late model black ringed shutter) for $135.

Time involved:
About an hour to get everything apart without tamper marks, and carefully back together without any dust in there.