I have recently acquired these two lenses which look like book ends. They are very heavy as the supports are cast iron; the inserts are brass with one of the lenses being made to unscrew which I presume means a different one can be inserted. I believe both are of the convex type. They are extremely well made.
When I obtained them I was hoping that an image could be formed when the two lenses were placed close together and this proved correct as shown in the attached images. My question is could they have been used in experimental photography or are they earlier than that? The image formed I believe is too small to be used for sketching purposes and it would be difficult to do that anyway. Maybe there is another purpose - Excuse the pun, but if anyone can throw light on their use I would be gratelful. If one lens is used on its own the image is larger but not distinct and has many abberations.
Thanks,
Mike Deane
oldphoto@cwgsy.net
www.deanephotos.com
Comments
Thanks, Mike. The only alternative set-up I can come up with might be a small part of some sort of array to demonstrate, say, the solar spectrum? I'm guessing that it's solidity and weight would make it ideal for demonstrating science to students on a bench, the sort of equipment that would take a lot of handling in the classroom, but that's merely a hunch. The important thing is to have fun with it, and experiment!
PK
Peter, Thanks , yes maybe - A teaching aid did cross my mind also.
Mike
I might guess it is a sort of "Camera Obscura" to assist and artist with the composition of an image for drawing/painting.
Wilson
Sorry Wilson!
Thanks Peter, It maybe but it looks a bit clumsy for that.
Mike
Hello Mike. You say that the aberrations disappear when both lenses are used. If these are chromatic aberrations, what you appear to have here is an achromatic couplet - one of flint, and the other of crown glass, similar to what you would find in the object glass of an achromatic telescope. The configurations of the lenses might be different, if both are biconvex, but the principle is the same. What this set-up might have been used for I can't say - demonstration perhaps? Crown and flint glass can sometimes be of slightly different colour. Hope this helps.
Peter Klein
Thanks Peter. There are still some aberrations there, but they are not so pronounced.
I do not think in this case they are of different glass as they are both the same colour - I have some other lenses that are though. So I know what you mean.
Mike
Following on from my post,on researching further, I have found out that using two double convex lenses can make a very basic microscope. Though I have found details of experiments to form a flat image with one double convex lens, to date, I have not found any mention of experiments being made to show an image with two loose lenses.
It is amazing how bright the image is considering it is not enclosed somehow. I am now about to fix a crude f stop in the middle, though this would make the image darker, the image should be sharper.