Re: how to work out shims
I think you misunderstand shims, but will leave the explanation to someone else. Your macro does not have a shim because it is a macro.
Re: how to work out shims
Are you referring to spacing rings used in mounting lenses to a barrel or shutter? If so, they are used to precisely position the lens elements at the right distance from each other and the aperture so that the lens is properly in focus. To determine what shims are needed, if any, and their size and position, one needs a sophisticated optical bench and very precise measuring equipment. It's not something that can normally be done at home...
If you're referring to something else, then you need to elaborate a bit so we understand.
Doremus
Re: how to work out shims
The lens spacing with the shims will let you control flatness of field for infinity and closeup. Closing the aperture can also change focus, so you might need to expose film at working apertures, rather than try to examine the edges of the ground glass with the lens wide open to find the best lens spacing for your purposes.
Re: how to work out shims
OP, where is this shim you mention? If it is between a cell and the shutter, it is there to compensate for a slightly off-specification cell. If it is between the back of the shutter and the lens board, it is there to provide clearance for the diaphragm's actuating lever.
Re: how to work out shims
thanks for the replies
the shims i’m referring to are the ones between cell and shutter
in the case of my 210macro it’s in a Sinar DB shutter
but it’s the same sort that’s in a copal or compur shutter
best
robin
Re: how to work out shims
Quote:
Originally Posted by
brighamr
thanks for the replies
the shims i’m referring to are the ones between cell and shutter
in the case of my 210macro it’s in a Sinar DB shutter
but it’s the same sort that’s in a copal or compur shutter
best
robin
But not necessarily the same thickness. That will vary from none to some depending on the specific shutter and lens.
Re: how to work out shims
Quote:
Originally Posted by
brighamr
thanks for the replies
the shims i’m referring to are the ones between cell and shutter
in the case of my 210macro it’s in a Sinar DB shutter
but it’s the same sort that’s in a copal or compur shutter
best
robin
If it came with the lens it is what's needed. The only thing you have to do is not lose it if you move the lens to another shutter.
Re: how to work out shims
Also possible any shim has already been lost
New user will not know
Quote:
Originally Posted by
Dan Fromm
If it came with the lens it is what's needed. The only thing you have to do is not lose it if you move the lens to another shutter.
Re: how to work out shims
so getting back to my actual question
"how is the need and thickness of shims calculated" ?
I'm quite happy with my lenses some of which have shims and some do not
best
robin