The knack is to use your knee to clamp the one end
Once you get over 60 inches you are in custom territory since most framing material is 32x40 with a subset at 40x60. Once you get over 60 inches your options for material are really limited since very little mat board is manufactured over 60 inches. For cases like this, I would agree you probably need to do it yourself. High end computerized mat cutters canít cut over 60 inches so wholesalers that save money by manufacturing in volume canít help.
If you are not going over 60 inches, then it is tougher call. If you can get a sheet of Bainbridge archival 4-ply for $10 then a pair of 18x24ís will cost you $5, but if you buy in qty 25 from an online wholesaler they might cost $5.27 each + little more for shipping. If it is worth your time to save 50 cents, or you cant by 25 at a time, or every may you cut is a different size then you want to consider getting a mat cutter and learning to cut mats.
In my case, even though I am an amateur photographer that owns a frame company, I have never hand cut a mat and never will. I would rather be taking pictures.
Originally Posted by jamie young
I have no axe to grind here as I offer no services, but I think I may offer a different view (mine only) on the matter of matting "non-standard" perspective photos. I currently present photos in 3 different (approximate) aspect ratios: 4:5, 3:5 (both horizontal and vertical) and 1:2 (horizontal only, my "panoramic" at this time), in many sizes ranging up to 40 inches, longest dimension. Every photo of identical LONGEST dimension is mounted in the SAME size mat and frame.
To use your example of 8X20 (closest in ratio to my 1:2):
16X20 (4:5), 12X20 (3:5), and 10X20 (1:2) are all matted to 24X30. This particular size, bottom weighting, etc. is a matter of personal taste and much discussion off topic here. (May as well start with AA's recommendations in "The Print", as anywhere else).
Obviously as a photo becomes more oblong, there will be more empty mat supporting two of the borders of the picture - but the short dimension will have identical borders to all other aspect ratios of prints of the same longest dimension. The advantages are two-fold: (1) photos of varying perspective can be shown together in identical frames, lending consistency to the exhibition (wall), and (2) only 1 size frame need be purchased for each base size (i.e., all aspect ratios of any particular longest dimension). The cost of using more mat and frame than might be otherwise necessary for increasingly oblong sizes can be offset by the ability to purchase multiple frames at price breaks and the cutting of (though I do cut my own) matboard. Also, I have personally found that as the print becomes more oblong, particularly in horizontals, it "requires" more mat at the top and bottom to "support" the work - it becomes a kind of negative space, separate from the hanging space (wall).
I have shown work this way for some time and have never had a complaint about the aesthetic of showing differing perspectives together. In fact most people don't notice the difference. They only notice the work (the print) - and isn't that as it should be?
For a 12x27" panorama, I added 4" on each side. I had my mat & frame custom cut, and got glass from a local guy.