I recall some time ago seeing a web site that described how to find the optical center of a frame when mounting a picture. This center is actually a bit higher than the geometric center of frame. Does anyone know how to calculate this position?

-- Michael Riccomini (mriccomini@bak.rr.com), December 18, 2000

Answers

Michael, uhhhh.... do you really want to find the mathematical center? Can't help you there. I think 99.9999 percent of photographers and artists probably do that visually.

You are right, you need to leave a little more blank space at the bottom, otherwise the image looks as though it is too low. Start out with a quarter inch, and go from there.

If you have a small image, say 4x5, matted to 16x20 inches, then you might investigate having the image quite a bit off center, towards the top.

That's about all I can contribute to this.

chris

-- Christian Harkness (chris.harkness@eudoramail.com), December 20, 2000.

opppps, I meant to say 'optical center.'

chris

-- Christian Harkness (chris.harkness@eudoramail.com), December 20, 2000.

A good rule of thumb for me has been to split the mat space 55% below the image and 45% above.

-- Sal Santamaura (bc_hill@qwestinternet.net), December 20, 2000.

The site you are looking for is at http://carbonphoto.cicada.com/tips/mattingtip1.html What I would like to know, and what is not explained in the article, is what exactly is the "optical center"?

-- Alan Shapiro (ashapiro@yorku.ca), December 20, 2000.

Thank you. The web site listed is exactly the one I was looking for.

-- Michael Riccomini (mriccomini@bak.rr.com), December 21, 2000.

Here's a trick I've used to center the optical axis while photographing flat art. Take a lens cap, poke a dead-center hole in it. Then pull a long piece of thread thread thru. Put lens cap on camera lens, and if the thread's length is the same at all four corners of the frame, you're on axis.

-- Standish Lawer (sdl@sni.net), December 29, 2000.

Generally I'll center the photo horizontally, then leave the same amount of space found on the sides of the image onto the top. If I don't have enough space at the bottom, then I am using the wrong size frame. I will usually dry-mount the image in place, so I can make measurements to cut consistent mats. I'm not sure if all my prints are at optical center, but among the varied techniques contributed, this one always works for me, at least visually.

-- Mike DeVoe (cameraservice@gci.net), January 23, 2001.