Graflex.org

Les · Joined: 09 May 2001 Posts: 2682

Bahgdad.

45PSS · Joined: 28 Sep 2001 Posts: 4081

and Bahdgdad gets its supply from the CIA.

Dan Fromm · Joined: 14 May 2001 Posts: 2165

Quote:

On 2003-05-07 20:11, RichS wrote:

Dan: Is there a simple equation you use to find out the vignetting in such a case? I know I could get out the graph paper and old geometry books, but asking is a whole lot easier :wink:

<snip>

Rich, I usually just draw a picture.

|
X______________|_____|

N A B

X marks the position of the lens' rear node.

The single pipe marks the position of the front standard.

The double pipe marks the position of the film plane.

Call the radius of the hole in the front standard r. The radius of the circle covered at the film plane is r* distance N-B/distance N-A. And there you are.

Long lens, short bellows, small front standard make for a small circle at the film plane.

As I said, similar triangles. Doesn't take graph paper, a scale model isn't required. You just have to get the idea.

Cheers,

Dan

RichS · Joined: 18 Oct 2001 Posts: 1468

Thanks Dan! Another one I'll have to save and try to remember where I put when I need it. And I'll have to run a few numbers through it to see what kind of lens I can hang in front of a 4x5.

But for now, I'm off to Baghdad :smile:

Dan Fromm · Joined: 14 May 2001 Posts: 2165

Quote:

On 2003-05-08 20:17, RichS wrote:

Thanks Dan! Another one I'll have to save and try to remember where I put when I need it. And I'll have to run a few numbers through it to see what kind of lens I can hang in front of a 4x5.

But for now, I'm off to Baghdad :smile:

Going to eBay costs less and is less hazardous.