problem with a Septon f2 50mm lens

rolandberry RemoveThis @hotmail.com (RolandRB) wrote in message news:<52970945.0409010744.3f384b7 RemoveThis @posting.google.com>...
 > rolandberry RemoveThis @hotmail.com (RolandRB) wrote in message news:<52970945.0409010005.37d8e118 RemoveThis @posting.google.com>...
  > > I'm posting here because I know somebody here can help. I have a
  > > Septon lens that does not focus at infinity (more like 17 feet). The
  > > front element group screws off and I suspect that the screws
  > > underneath in the housing are replacements that are too proud and it
  > > is stopping the front element group from srewing in as far as it
  > > should, hence affecting the focus. Could somebody send me or direct me
  > > to a side-on picture of this lens so I can do a comparison?
 >
 > There's this
<font color=purple> > <a style='text-decoration: underline;' href="http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=707&item=3835711964&rd=1&ssPageName=WDVW</font" target="_blank">http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=707&item=3835...964&rd=</a>>
 >
 > ...but I need it focussed to infinity.

It was a simple fix. Just unscrew the front and back lens assemblies,
unscrew the three screws, take the machanism out and screw it so the
lens would be further back and then reassemble and repeat the process
until the lens was in the correct position for infinity.

But I noticed something else that would apply to many MF cameras. The
focussing screen has a split prism in the centre. I have found these
previously to be always accurate, but in this case I have a feeling it
is not accurate. Surrounding the central split prism is an area of
tiny prisms that look as though it is plain glass when it is in focus
but you can see the prism effect when it is not in focus. They do not
agree. I have to go "past" infinity with the central split prism to
get the surrounding prism area to go to plain glass mode. This sort of
effect would apply to many MF cameras. Has anyone else noticed the
same.<!-- ~MESSAGE_AFTER~ -->
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