Sinar Board and Copal 1 Shutter Problem

[Richard K.]

I knew about this possible problem but then (in)conveniently forgot about it until I looked carefully at my Fujinon 450 CS! It didn't seem quite as sharp as I remember it being when I owned one before and I wondered why. Well, it seems thet the thickness of the (possibly not genuine but it sure looks like it is) Sinar #1 board doesn't allow the rear barrel to screw completely down. One needs to rout out a bit for the retainer ring. I confirmed this by counting rotations required to set the barrel into the shutter with and then without mounting on the Sinar board. They differed by by almost a full rotation. You also don't get that nice Klang/chunk/tik sound at the end and more forced turning is possible. The problem (same number of turns) was solved when I used a Sinar clone with a channel routed out for the flange (although I haven't confirmed yet by taking a photograph). Would one turn make a difference in sharpness? Comments?

[Richard K.]

Nobody else has ever had this concern? :confused: :eek:

[LynnRB]

Same problem with my 90mm Grandagon. Lynn

[Richard K.]

Same problem with my 90mm Grandagon. Lynn

Did you notice any sharpness problems?

[Sevo]

Common problem - some sinar boards (in particular those with cast reinforcement bumps and rim) are too thick for many wides. In the past I helped myself by using cheaper, thinner Horseman boards - currently most of my lenses are DB mounted, where sinar sorted out that problem for me or some past owner...

[Ken Lee]

You might consider putting your shutter-mounted lenses on Technika boards - and using a Technika-to-Sinar adaptor board.

It saves a little room and weight, and won't create the problem that the Sinar boards can.

[ic-racer]

Perhaps an alteration in field flatness, but I'd not expect overall loss of sharpness.

[Tracy Storer]

On full turn of the rear cell is 0.75mm or just under 1/32".....some lens designs spacing is more sensitive than others....1/32" would be a lot depending on the lens. (probably anything in a smallish shutter like a C#1)

[Richard K.]

Perhaps an alteration in field flatness, but I'd not expect overall loss of sharpness.

Yes exactly! And it was driving me nuts!! SO 1 turn off can do that?!?

[Bob McCarthy]

You might consider putting your shutter-mounted lenses on Technika boards - and using a Technika-to-Sinar adaptor board.

It saves a little room and weight, and won't create the problem that the Sinar boards can.

Ken,

I've been think about going this way myself. Does someone make a high quality adapter. I've seen a few that looked kind of cheesy.

bob

[Tracy Storer]

Don't think of the focal length, or the physical size of the lens, think of the air space between the front and rear cells being changed by whatever percentage 1/32 of an inch represents.
If that airspace is 1", 1/32" represents 3%+ of that distance. The airspace is probably less than 1" which makes a 1/32" difference an even bigger deviation from the design. Remember, the airspace is part of the design, the lightpath through that air is know and planned for, why would the performance NOT be affected with the rear cell in other than the designed position.
Think of other things being 3%-10% off plan and how well or poorly they would work.

[Sevo]

Don't think of the focal length, or the physical size of the lens, think of the air space between the front and rear cells being changed by whatever percentage 1/32 of an inch represents.


In many lens designs (indeed most current LF lens schemes) changing that airspace will first of all change the focal length and to a lesser degree the curvature of field. I have doubts whether it will affect the performance of double Gauss/Symmar types significantly - altering the air space was routinely used whenever shimming their process lens versions to match focal lengths to the camera or enlarger scale.

[Keith Pitman]

jinfinance, a seller on Ebay. I have an adapter board, and Linhof lensboards from him. Very well made. Prompt shipment, usually (e.g., if in stock).


Ken,

I've been think about going this way myself. Does someone make a high quality adapter. I've seen a few that looked kind of cheesy.

bob

[LynnRB]

Did you notice any sharpness problems?

I never used the lens that way. The spacing of the cells is critical for good definition. i milled the backside of the board so the ring seated deeper.