[LargeFormat] Lensboard

[Clive Warren]

At 11:43 am -0500 12/12/01, Robert Mayrand wrote:
>Hi!
>I know there is no standard in board size but is there any in board
>thikness. I'm using a large format camera for the first time and have to do
>a board and mount the lens.
>
>Are we suppose to screw the back element as far as we can. On my lens the
>retaining ring is pretty thick if I screw the element as far as I can with
>the ring it leaves less then 1/8" and it seem pretty thin.
>
>The size of the hole also raise some concern. The ring has a shoulder wich
>goes to 1 5/8". Should I do the hole of this side. Or to the actual smaller
>thread size of the lens.
>
>MY lens is a Symmar-S 180mm mounted in a compur 1
>
>Thank you for you help.
>
>Robert

Robert,

Ah, just what I've been doing for the last two days - trying to find 
the right combination of lens board, lens, mounting ring/flange and 
camera.

There are plenty of standards out there - each camera manufacturer 
has/had their own. This can be a real pain. I am thinking about 
standardising on a 4x4 metal board and making 4x4 metal board 
retainers on the wooden boards for various cameras here.

The rear element set of any lens should be screwed completely home - 
the distance between the front and rear elements is critical.

Most contemporary lenses (shutters) are designed to be fitted to thin 
metal boards using a simple threaded retaining ring. If you want to 
mount one of these lenses onto a wooden board then you need a 
threaded front flange mount that is secured to the front of the lens 
board using (usually) 3 or 4 small screws.

One alternative is to fabricate a flat metal plate with a hole in it 
to accept the shutter and then mount that on to the front of a wooden 
lens board. You can then use the retaining ring as normal.

Modern shutters typically do not have a long enough mounting 
shank/threaded part to reach all the way through an old wooden lens 
board.

Any hole drilled in a lensboard should be large enough (just) to 
allow the shouldered part of the retaining ring to fit in the hole. 
Make sure that the shoulder is not longer than the thickness of the 
lens board though.  If this is the case, reverse the retaining ring 
as long as there are enough threads from the shutter body shank still 
in the retaining ring it will be safe.

Steve Grimes will make almost any type of retaining ring/flange that 
you can think of for a price. http://www.skgrimes.com/

Good luck.

Cheers,
        Clive