Info needed on cement used in 90mm Angulon

[Martin Courtenay-Blake]

I have a little 90mm f9 Angulon in a Compur shutter. I think it has been dropped as one of the aperture blades has been displaced (which I can deal with) and there is some seperation between two elements in the front group. The seperation covers about a third of the interface between two of the elements and is only visible at about 45 degrees to the lens axis. Does anyone have any info as to what adhesive Schneider used on these lenses as, inspired by other posts on this site, I would like to attempt re-cementing the front group.

I haven't tried using this lens yet as I have to fix the aperture blades, so I don't know if the seperation has any real affect on image quality, but I suspect it will. If re-cementing is a no go then I'll bin the lens and salvage the shutter.

[IanG]

They would be mainly using balsam as they predate the switch to newer synthetics.

Ian

[erie patsellis]

I'd suggest trying it first. The angulons varied from excellent to rather poor. There is always the option of wicking in a bit of very lightweight oil to ameliorat the effects of the separation. Google Rick Oleson for more info.

[Bob Salomon]

"90mm f9 Angulon"

Really?

[Martin Courtenay-Blake]

"90mm f9 Angulon"

Really?

Whoops, too much Christmas cheer...... f6.8

[Martin Courtenay-Blake]

Thanks for the info and suggestions. Think I'll try a couple of shots first to see how bad it is. If clearly visible thinkI'll try re doing the balsam. If I mess up there are plenty around. Just seen a really nice grandagon on Ebay at a good price which could tempt me.

[Steven Tribe]

The serial number should give you the production date. Experiments with synthetics began quite late 40's/50's?.
Is it just Newton's rings or a visable opaque area?

[Martin Courtenay-Blake]

Hi Steven, I've been following your exploits with balsam with interest and it is that which tempted me to look at this Angulon. The seperation is scallop shaped from one edge to almost the centre. I'm not sure which of the three elements in the group is affected. The total area is about 1/3 or the lens area and it actually looks like a bubble. My first impression was that a piece had broken of one of the elements but I am leaning more towards some sort of traumatic seperation. As I said before it is completely invisible if you look directly into the lens and it is only really visible in reflected light at an angle of 45 degrees or more. I'll check the serial number to get a rough date of manufacture.

[Ole Tjugen]

An Angulon with separation in the front cell is well on the way to become a doorstop - except that it is too small and light to do a good job at that.

It's only the cement holding the lens elements in place, and once the cement fails you no longer have a useable lens!

Try heat treatment in a vacuum chamber, holding it absolutely horizontal during the process. Or, alternatively, get another one: They are too cheap to spend the kind of time and/or money a repair would cost on.

[Steven Tribe]

Try heat treatment in a vacuum chamber

Not many of us have these handy!

Sounds like balsam breakdown. Edge shears are not usually as you describe and they have a ripple pattern.
I'll have a look at my angulon tomorrow and see how it is built up.

The position of the boundary, between general servicing (in which I include many rebalsaming exercise) and throwing something away or sending off to technicians, is very different for us all. Perhaps I am being over romantic, but I enjoy bringing some back to an active "life" - no matter what the real value of the item may be.

No "doorstops" in my home!

[patrickjames]

Recementing lenses is not difficult to do if the cells have the exact same diameter. Your Angulon, if I am not mistaken, has different sized elements. Your best bet would be to go the oil route knowing that eventually it will be toast. Unless you have the equipment to do so, there is no practical way to align the elements again once you get them apart. You will end up with a real bowzer if you separate them.

[Steven Tribe]

Figure Sc014 in Lens Vade Mecum shows a mushroom-type construction. Two of the lenses have exactly the same diameter, while the third (outer lens) is quite a lot bigger. Should be relatively easy, as there is only a single problematic balsam operation.


Unless you have the equipment to do so, there is no practical way to align the elements again once you get them apart.

This is just not true! Checking the correct alignment of cemented lenses can be done quite accurately with a thin beam of light and refections. If it is faulty - try again before the balsam becomes to hard. Collimation is necessary for series of separate lens in adjustable mounts.

[patrickjames]

is[/B] necessary for series of separate lens in adjustable mounts.

I would love to hear more about this method Steven.

[Steven Tribe]

I'll try and illustrate the laser/thin beam system when I next do a re-cementing (DIY section).
The basic logic is that, although the spherical join won't show any change in refected light if the join is off centre, the inside surface of the second lens will be at a slight angle if the join is not dead centre. A central pinpoint of light will not be reflected in this situation from the last surface so that it aligns exactly with other reflections in a straight line, revealing the cementing is not central.