The easiest and most common mat layout is one with the widths of all four borders equal. If you are forcing a picture into a standard-sized frame, however, that’s not always possible. And then there’s the matter of bottom-weighted mats.
Bottom-weighted mats, or mats with the bottom edge wider than the others, were introduced long, long ago. Some say that pictures centuries ago were hung very high on the wall and the bottom width of the mat was increased to compensate for the ‘distortion’ of that perspective. Unfortunately, that story makes no sense; top-weighting would be required to correct for the top being further from the viewer than the bottom. Another explanation involves the notion of a difference between the visual or optical center and the geometric center. Yet others claim it is to compensate for the drop of the mat in the frame due to tolerances necessary to account for expansion, etc. For whatever reason, bottom weighting could be seen as an attempt to fool your audience or overcome optical perceptions, whichever you prefer. As commonly practiced in “finer frame shops everywhere”, the bottom width is generally increased ¼” to 1″, depending on the size of the picture.
Using Standard Mats
But how would one incorporate bottom weighting while fitting an image into a standard-sized mat? For example, if the vertical difference between the hole size and mat size is greater than the horizontal difference, and assuming the left and right borders will be the same width, is it better to:
|A||Make the top and bottom borders equal,|
|B||Make the top the same size as the left and the right and put all of the extra width on the bottom,|
|C||Make the bottom larger than the top by some fixed amount,|
|D||Make the differences even more subtle by making the difference between the top border and the side borders the same as the difference between the top and bottom borders?|
Let’s clarify your choices with an example. Suppose you want a 4″-high hole that’s 7″ wide in a standard 8″-high by 10″ mat. The horizontal difference between the mat size and the hole size is 10″ – 7″ = 3″, so if you want the left and right borders to be the same, each will be 3″ ÷ 2 = 1½”. The vertical difference between mat and hole size is 8″ – 4″ = 4″.
|Choice A||Would make the top and bottom borders the same, making them each 4″ ÷ 2 = 2″.|
|Choice B||Would make the top 1½” like the left and right borders, leaving 4″ – 1½” = 2½” for the bottom border.|
|Choice C||Uses the customary bottom weighting, which the one reference I give above lists as ¼” for an 8″x10″ mat (personally, a ¼” bottom weight isn’t worth the trouble). That means the top border would be (4″ – ¼”) ÷ 2 = 1⅞” and the bottom would be ¼” more, or 2⅛” (notice as you check your work that 1⅞” + 2⅛” = 4″). Finally,|
|Choice D||Is a tad more complicated. Let’s call the difference between the left or right border width and the top border width “d”, such that|
|1½” + d = T (for top border width).|
Then the bottom border (B) would be
T + d or (substituting the last expression for T)
(1½” + d) + d = 1½” + 2⋅d.
Since T + B = 4″, then (substituting for T and B)
(1½” + d) + (1½” + 2⋅d) = 4″, meaning
3″ + 3⋅d = 4″ or 3⋅d = 1″, meaning d = ⅓”,
so (substituting back into our equations for T and B)
T = 1½” + ⅓” = 15/6” and
B =15/6” + ⅓” = 21/6”
(again noting that 15/6” + 21/6” = 4″) .
The choice you make would be an artistic decision, but I think A is the most common answer. Choice C could be used for traditional bottom-weighting, as in our example, or could be used for some other more artistic value. Technically, both Choices B and D are possible results of that equation. B would be exactly what you get when you want bottom-weighting and are not restricted to standard mats; it would work best if the resulting difference between the top and bottom borders is not too much greater than the customary bottom-weighting distances mentioned above. In our example, it yields 2½” for the bottom border, which is an inch larger than the other three borders and may just be too much. In our example, C and D are very
With Larger Side Borders
If the horizontal difference between the hole size and the mat size is greater than the vertical difference, you could face up to the same number of choices as above, but you are working with less material for the top and bottom borders and I think it is usually better to keep things simple and make those borders equal.
Differing Left And Right Borders?
Do the vertical borders always need be the same size? Although I can’t say I’ve ever seen or read about different-sized side borders, I’m not convinced that uniformity is strictly required. For example, in photography, as in older art forms, there a “rule” of
I present the above thoughts to give some background and (more importantly) stimulate your own creativity. If you think of other possibilities, I’d be thrilled to have you add them to the comments. Thank you!