Matt Board Aperture Calculator

As a few people got photographs from me for Xmas this year I had to cut a few matt boards (or mat boards for the American readers). I don't have a fancy matt board cutter with stops or cool measurement systems (I would love a Speed Matt) so I basically measure and draw on the back of the matt and then use a Logan cutter to cut the aperture.

As I don't like the photo to be centered on the frame I came up with a script to generate the cutting measurement for me using two different methods. The methods are the 'Optical Centre' and the 'Weighted Centre'. The 'Optical Centre' is detailed here, while the 'Weighted Centre' is detailed here.

As I work in mm, the script is designed so you input mm, but if required, you can enter the " mark to indicate that the measurement is in inches and it will convert to mm (eg 16"). The script is also written so that the measurements from the edges are in whole numbers (rounded up) - there is nothing more tricky that trying to measure 30.33334mm

After entering the dimensions of the frame and picture, an optional reference (eg picture name), deciding on how much overlap you need and the centering method hit Calculate Matt and an image will be generated that you can print out and then use for measuring the back of the matt.

I keep my mum happy, I have added the ability to enter a +NN in the frame width and height if you are having a custom frame made and want to enter the gap between the picture and frame rather than the actual frame dimensions (note that you must be working in mm for this). As an example, if you want a 40mm gap, then enter +40 into the frame width and height. The +NN number will then be doubled and added to the picture dimensions and then the selected centering method will be used.

Shown on the image are dimensions if you are measuring from each edge, in addition to the method that I use for measuring (from the top of the matt board for the upper and lower cuts, then from the centre to get the left and right cuts.

Frame Width
Frame Height
Picture Width
Picture Height
Overlap
Reference
Centering MethodOptical
Weighted
Centered