View Full Version : Sinar P2 8x10 DOF scale for idiots

Uri A
20-Dec-2010, 06:04
Hi all,

You know that Sinar trick with the focus far, focus near, zero the scale and transfer the angle to the rear standard thingy? I don't get it. And why is it always exactly 2 stops to roll in??

I know there are previous threads on this but I am a very, uh, lets say "right-brain" kinda guy and if anyone says anything about circles of confusion, I will get confused! I don't like numbers either....

Anyone know how to talk to special people?


erie patsellis
20-Dec-2010, 13:32
Well, it's pretty straightforward.

Focus far, zero scale, focus near and read off required aperture. Then move back 2 stops to expose. (to shift the actual focal point to the center of the DOF range needed)

Practice it for a while and it becomes second nature.

If you're talking about movements (swings/tilts)then that's not what it's for. Depending on whether you have an F, C or P, the procedure is slightly different. Tell us what you have and maybe somebody can help more.

Bob Salomon
20-Dec-2010, 13:58
Not a "Sinar trick" Linhof also uses a version as do some of the other monorail cameras.

Jeff Conrad
20-Dec-2010, 19:44
The mathematics are really very simple, and the same principle was used on hand-camera DoF scales long before it appeared on LF cameras. For an explanation, see the Wikipedia article Depth of field (http://en.wikipedia.org/wiki/Depth_of_field). It's discussed in the section Focus and f-number from DOF limits (there actually are two sections with that name: the second gives a more detailed explanation, including the derivation). The section Zone focusing explains how the principle is applied to hand-camera lenses; you should notice a remarkable similarity to what you described in your original post. Though the small-format people say otherwise, the technique also works on tilt/shift lenses with tilt, provided one recognizes that the marked distances are no longer meaningful.

I've used this approach to set focus and f-number on every type of camera I've every had, and honestly don't know how to do it any other way.