PDA

View Full Version : Compensating for an off centre lens board



andrew gardiner
12-Feb-2013, 11:52
Hi there, I'm very new to LF and am just about to set off for the first time with my Wista VX on a serious and remote trip. My problem is I have at the last minute received a 180 Nikkor W 5.6 and they've mounted it on an off centre lens board presuming I was using a Wista wooden field camera.

Is it straightforward for me to compensate for this using front rise? Will it add complications? Does anyone have any advice for an absolute beginner? As well as shooting 4x5, which has a gridded gg, I also have a 5x7 adaptor back which I am wanting to use which doesn't have any markings.

All advice hugely appreciated

Andrew

C. D. Keth
12-Feb-2013, 12:10
You can measure the offset and make yourself a second witness mark if you want. In practice just use your eyes and don't worry about if the lens is perfectly centered or not.

With the ground glass, get a very fine pigma micron pen and draw a grid on it yourself. I use a .25mm pen but you could go heavier of you like a more visible grid. Wash the groundglass first with doh soap and hot water. Write on the ground side, keep even pressure, and do it in one motion without slowing or stopping and you'll get even lines.

andrew gardiner
12-Feb-2013, 14:06
Thanks very much C.D. Sorry to be a dullard - second witness mark?

C. D. Keth
12-Feb-2013, 14:24
Witness marks are those markings on most cameras that you align to set the camera to a "zero" point.

Bob Salomon
12-Feb-2013, 14:35
A genuine Wista lens board is off set the same way, and the same amount, as a genuine Linhof lens board with the same hole size.

This is so the optical center of the lens will be centered on the ground glass when the front standard is all the way down (the standard not the drop bed). That means that you do not have to compensate for the lens position at all.

The Wista RF, VX and SP metal cameras use exactly the same lens boards as the DX and other Wista wood 4x5 field cameras.

Worry less and just shoot.

andrew gardiner
12-Feb-2013, 18:04
Thanks C.D. and thanks Bob, I only really noticed because my other lenses are centred.

C. D. Keth
12-Feb-2013, 23:25
Worry less and just shoot.

Hear, hear!

Doremus Scudder
13-Feb-2013, 02:32
Bob's your uncle, as usual here.

Now, you may be worrying (oops, you're not supposed to do that, but just in case you are...) about your lenses mounted in centered boards.

But, stop worrying about that too. The lenses you have on center-drilled boards now just have a bit of built-in rise. This is often very helpful for short lenses and cameras with limited bellows movement or getting that bit of extra rise out of the camera (you might want to dedicate your center-drilled boards for this purpose, i.e., for lenses that you tend to use lots of rise with).

You may now want to make a second witness mark for your lenses on center-drilled boards, as C.D. suggests, although the amount of offset is not going to make any real difference in image quality. However, if you want that optical center in the center of the film, measure and then make a little mark and then use a bit of drop to position the lens more perfectly when setting up.

Most of us, especially when shooting scenes with parallel vertical lines in them (anything with buildings in it, forests with trees, etc.) usually set up the camera with the back level and then frame using the front rise movement. That means that the lens is off-axis most of the time anyway for reasons of composition (that's why we have cameras with movements, isn't it?). I have to use a lot more rise than the difference between a center and off-center lensboard to get any kind of softness in the corners even with the rather modest-coverage lenses I use, so you shouldn't be overly concerned here.

FWIW, I have a couple of cameras that take Technika/Wista boards that allow the lens board to be mounted rotated 180. I find this really helpful in conjunction with an off-center lens board; I can mount the lens upside down and get a significant amount more rise (the offset x 2) than I can with just the rise movement. I've often wanted to design a camera that took square rather severely offset lensboards, which could then be positioned in any of four orientations to enhance rise, fall and both shifts. Maybe someday.

Best, and good luck,

Doremus