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.
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
"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
The optically-centered print is slightly above center. In some cases, this is more visually pleasing, because of an illusion in which a vertically-centered print seems to “sink” a little on the mount.
The following script calculates the print position and illustrates it graphically.
The units are arbitrary. Fractions are optional.
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.
Run this document as a smart phone app! Specific instructions on how to do it on Android here.
Photoshop script
Some members of the Photoshop community have tried the optical centering concept, by expanding the canvas then centering the original image on a virtual mount. See
Photoshop User TV: Episode 253 for a demonstration.
Here is a photoshop script, Optical_Centering.jsx, that should do the job.
It should be self-explanatory. If you enter a rabbet width, the hidden edge of the mount is colored black. If you enter a mat space, the mat is colored gray so you can see the space. You can recolor or uncolor it as needed.
Tested in CS2 and CS5. You may need to flatten the image first. Settings are saved to an .ini file in your default user folder. Updated 2/1/2011.
Just to point out, if you are wanting to print an image optically-centered on a mount-sized piece of paper, you might try calculating the print position, then using it as the top margin in the print dialog.
Tested with Firefox 3.6, Internet Explorer 6, Safari (for Windows) 4.0, Opera 9.64,
Fennec (for Windows) 4.0, Dolphin Browser HD 6.0.0, Dolphin Mini 2.11,
xScope Browser - Web & File 6.43.1,
Miren Browser 1.2, and Boat Browser Mini 2.4.
"Pierre Renault" wrote in message
