Fujinon A 240mm f/9 with Sinar autoaperture shutter

**kunlun121** · 21-Aug-2021, 02:29

Hi everyone,

I'm trying to figure out if it is possible to use this lens DB mounted for use with the Sinar auto aperture shutter. After some google research I found one old listing somewhere of a Fujinon A 240mm f/9 DB mounted, but usually these lenses are offered with a Copal #0 shutter.

It's one of these I'm thinking of buying, but would like to use it with a Sinar auto aperture shutter. I am told by someone with lots of large format tech / mechanical expertise that the lens fits on a Sinar DB board with mounting threads and spacing for a copal #0 shutter. These can be found with little effort. The question is whether the Sinar shutter will be fully functional with this lens in the DB board. Apparently there is a risk of a mismatch between the aperture settings of the DB mount and the lens. Does anyone have any experience with this? It seems this conversion is mostly done the other way round, i.e. from DB mount to a Copal #0 shutter.

A search of this forum yielded an old (2013) thread with some information that looked promising. Unfortunately the relevant information was in a link that is now long dead... (A file linked to here (post #4) posted by erie patsellis on this forum.)

**Bernice Loui** · 21-Aug-2021, 10:13

Yes, this is do-able.

~240mm Fujinon A is native to a Copal or similar# 1 shutter.

Sinar made two basic styles of DB mount. First and most common is the DB mount with no markings or external controls of any kind. Second is the DBM, the M style DB mount has a manual aperture over ride control dial allowing manual control of the lens without the DB shutter controlling the aperture. Both styles were made for a long time, earlier styles of this DBM mount has a different physical appearance and aperture blade style. Functionally identical.

-Decide on which style of Sinar shutter lens mount to use.

The original shutter with the specific Fujinon 240mm A will need to have it's shutter distance checked to less than 0.001" accuracy with both lens cells removed.
Once this dimension has been recorded, the same is repeated for the Sinar DB or DBM lens mount to be fitted to the Fujinon 240A lens cells. If the recorded dimensions do not match, shim (s) must be applied to equalize the difference in dimension to preserve original optical performance.

~Once this has been achieved, setting the aperture becomes the next task. Could be done with measuring the aperture diameter relative to the scale on the original Fujinon 240 A's shutter then transferring it over to the Sinar DB shutter or using a Sinar behind the lens Booster probe, measure the effective light transmitted at the given lens apertures then using those values to set the aperture on the Sinar DB mount as driven by the Sinar shutter.

Bernice

**kunlun121** · 22-Aug-2021, 03:43

Thank you, that is very helpful.

You wrote that the lens is native to copal e.a. #1, whereas the information I have found states #0 (for example here). What I know comes from the internet and you probably have better sources. Could you explain why you advise a #1 dimensions shutter?

Could you provide some further guidance on how to transfer the aperture found on the Fujinon to the DB mount?

**Bernice Loui** · 22-Aug-2021, 11:05

Stand much corrected, the 240mm Fujinon A does come in a Copal or similar# 0 shutter. Change over will need a Sinar# 0 DB or DBM mount lens board set.

Once the lens cell spacing has been ascertained then transfered from the copal# 0 shutter to the Sinar DB/DBM lens mount (spacing adjustment as or if needed), the aperture size is set by this set screw on this slot. Once the set screw is loosened, the DB/DBM aperture size can be adjusted then set to what is required for the lens cells to match the scale on the Sinar shutter.