Optical Print Centering

Pierre Renault in rec.photo.darkroom posted a very interesting method of optically centering a print on a mount. Here is my equation that determines the position mathematically, and a graphic illustration of the results..

From: Russell
Subject: Re: Automatic optical centering - WAS: Square Format Framing - 1 attachments
Newsgroups: rec.photo.darkroom
Date: 2000-12-20 23:57:23 PST

Wm = Width of mount
Hm = Height of mount
Wp = width of print
Hp = height of print

Distance between top of print and top of mount = (Wm + Wp) (Hm - Hp) / 4Wm

--Russell

diagram

"Pierre Renault" wrote in message
news:9010E33FAcheungmomailandnewsc@205.237.233.50 ...
>
> Here's how to automatically optically center any print on any board.
>
> Place the print to be mounted in the upper left-hand corner of the
> board. If you are placing a print under a matte board, then place a
> piece of paper the same size as the desired cut-out.
>
> Bisect the vertical strip to the right of the print and draw a light
> line with a pencil from top to bottom. Do the same thing for the strip
> below the print. Draw a line from where the horizontal line crosses the
> vertical line you've drawn to the right edge of the board.
>
> Next, place a straightedge from the point on the right-hand edge of the
> board where the horizontal line ends to the bottom left-hand corner of
> the print. Mark the spot where the line intersects the line bisects the
> vertical strip.
>
> Place the lower right-hand corner of the print at this intersection.
>
> This works first time, every time.
>
> Pierre

(Archived in Google Groups.)

The following script calculates the print position and illustrates it graphically.

Include the space between the mat and print edges if appropriate. The preferred method is to center the mat window, but you may choose to center the print itself.

Rabbet width refers to the inner edge of the frame that overlaps the edge of the mount. In the illustration, the frame stock is 3x the width of the rabbet.

Sometimes optical centering results in the top margin being narrower than the sides. In that case, you will probably want to use one of the other centering options.

mount – width:
height:

print – width:
height:

space inside mat:

frame rabbet width:

optically centered window print
equal top and sides
vertically centered

draw rotate

print position – from the top:
from the sides:

mat widths – top:
sides:
bottom:

fractions decimals

1/16	1/8	3/16	1/4	5/16	3/8	7/16	1/2	9/16	5/8	11/16	3/4	13/16	7/8	15/16
.0625	.125	.1875	.25	.3125	.375	.4375	.5	.5625	.625	.6875	.75	.8125	.875	.9375