Lens Mounting to Shutter

Mounting Barrel Lenses in Shutters

Many graphic arts lenses can be converted to excellent picture taking lenses by mounting them in modern shutters.

See a 24″ Schneider Artar fitted to a new Copal #3 shutter.
  • This late model Schneider 24″ f-11 “Red Dot” Apochromat Artar is a perfect candidate for re-mount to a shutter. Shown in its original barrel complete with mounting flange.
  • Partial disassembly shows the four main pieces of a barrel mounted lens, from top left: the mounting flange, rear element group, front element group, and iris barrel. Everything is used in the final installation except the iris barrel.
  • Next the iris barrel is accurately measured to determine the original element spacing and iris position. Although the element spacing can be determined on the optical bench, in cases where the barrel is missing or has been altered it is best to transfer the original configuration of the lens to the new installation.
  • The measurements are noted in a simple sketch which is then used to program the Computer Lathe (CNC) to make the necessary modifications and threaded adapters.
  • In this case, there is no front adapter to machine. Instead, the front lensmount is re-threaded to fit directly into the shutter. This duplicates the original front lens-to-iris dimension and allows further measurement for the back adapter. The picture shows turning down the front part of the lens on a threaded arbor after removing the glass.
  • A digital readout fitted to the quill of a milling machine makes an excellent measuring device. Wherever possible single measurements are taken of actual assemblies rather than depend on additions of individual parts.
  • The modified front lensmount is assembled to the shutter, and the entire assembly measured to compare with the original barrel dimensions and calculate the thickness of the back adapter. With the readout set the same as the previously measured front lensmount with barrel, the distance to the flat table is the dimension of the adapter to be machined.
  • The back adapter is machined from Holobar aluminum stock. Although adapters can be machined from pre-prepared blanks, perfect concentricity and centering are ensured when all threads (shutter thread, lens cell thread, and flange thread) are machined as part of a single chucking operation. No matter how accurate the lathe is, there is risk of error when a part is removed and replaced prior to the next step.
  • With the front lensmount and shutter assembled to the unfinished back adapter, the exact cutoff measurement can be directly applied using the lathe’s digital readout. The distance from the front of the lens to the back of the rear threaded adapter is now accuratly acheived.
  • Using a digital dividing engraver, the iris scale is engraved onto the new shutter, duplicating the apertures in the original barrel. This one shows engraving of 1/3 stops at $10.00 additional charge. I can also extrapolate the scale to add a smaller f-stop (f-64 in addition to f-45, etc.) On Copal shutters the scales are engraved on both sides as intended in the design of the shutter.
The finished lens is shown at the top of this page.
The price for this work ranges from as low as $250.00 for small, straighforward mounts up to $500.00 for larger sized more complex installations, including anodizing. (It does not include the price of a new shutter.) The typical pricing to remount a lens into a customer provided shutter is $300.00 – $350.00.
Now, how about a Nice Lenscap?
© 2016 S.K. Grimes
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