broken len element in an old brass lens
I recently bought a 14" projector lens from an old magic lantern cheap off ebay, it was a bit banged up and dirty, anyway...
I managed to take it apart and clean it up, the brass cleaned nicely and except for a few stubborn marks looks good, the glass (which I expected to be a bit of a horror show) also came out spotless and except for a couple of chips near the edge on the rear elements was usable.
So I was happy, until, when tightening the ring on the rear elements there was a crack, crack went the element, and in half, broke clean in half.
Now I have a lens with 2 good elements and a decent body, but one, one that's now 2.
So is it worth trying to replace it?
Use it as a door stop?
Give it away to someone who can use the barrel and bits . . . . .
You did not tell us did you intend to do with it?
Glue the two pieces together. I would do it with UV-curing glue (need sunny day); do not use instant glue. Before you expose to sun, make sure they are precisely aligned, using the match of the crack surface and checking the surfaces and edges match.
- Either use as-is; at least do a first test
- Or, if you think you see objectionable flare, cover the region of the (glued) crack with a thin line of black paint. All you will suffer is a small loss of effecitve aperture (plus diffraction by the edges of the black region, but this should be negligible wrt te native geometrical aberrations).
When you finally re-mount the lens, use some foam or other between the ring and the glass; three small pieces in a triangle should be OK. Whatever method you use, make sure you preserve the centering as per the original design.
that would be a further option...
but I'm hoping someone with the bit I need will come along and give theirs away to me
I intended to use it on the camera I'm currently building.
Originally Posted by bernard_L
I might give that a go, but would prefer not to glue anything just yet... having said that, I can't make it any worse really.
Tomorrow I'll rig something up to see how bad it effects the performance.
Sponsored Ad. (Subscribers to APUG have the option to remove this ad.)
The curvature of the lens can be determined from one of the pieces. However you would have to find someone to grind a replacement for you. The lesson learned here is do not be hamhanded when working with lenses.
A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.
~Antoine de Saint-Exupery
how would I determine the curvature?
Originally Posted by Gerald C Koch
and I think the lesson here is that I'm a stupid boy with stupid hands
Sickening as the thought may be, I'm afraid it's finished.
tom, tom, tom, tom, tom
nothing is ever finished until the end... I see what you mean
At the camera fair I go to one stall holder was selling off the spares etc from a retired camera repair shop, about 18 months ago. I had quite a few shutters, there was also a box of lens elements all wrapped in their original wrapping material, some marked indicating what lens.
Another trader bought the entire box, as far as I know he still has them. I can find his details (I won't see him until July) if you're interested - he may be able to help. Let me know the diameter, he owes me a favour, and I can see if he has anything the right size, and then that matches.