These past years in the shop, I've taken an educational approach to selling our frame designs that support the art our clients bring in. The key phrase in that sentence is "support the art". We're all artists here, and often you'll hear me say "as much as framing costs can be, when you leave the room you want to remember the art and not the framing." Being artists, we use our color theory, knowledge of design and composition to enhance what your focus is on the art - not to distract from the visual.
As much as we try to apply our design knowledge to a client's work of art, we also know that it is their personal aesthetic that we are trying to achieve. However, there are fundamental "weight and balance" theories that shouldn't be ignored.
Examples "A" and "B" illustrate a balance with even borders. Image "A" has even sides on the mat with thicker yet equal sized borders on top and bottom. The image of the Calla Lilly is a strong vertical composition. Decreasing the width of the side borders of the mat exaggerates the vertical feel.
Example "B" is the same flower with a mat that has even borders all around it; a standard display yet, effective. This approach displays the art "as is" without influencing the viewer with the borders.
Used more with strong horizontal compositions in art, a bottom weighted mat (example "C") "supports" the flower. In the case of this image, the added width on the bottom border of the mat balances out the dark, negative spaces of the artwork on the bottom half of the painting. Conversely, it lessens the focus on the Lilly itself because the value of the mat equals the value of the flower (Compare example "C" to "B").
While I understand the need to stay within budget, squeezing your art into a ready made frame to get the visual effect of example "D" must be avoided. Thin top and bottom borders do not visually "support" the art and the wider side borders counter the natural vertical feel of this piece of art. The best rule of thumb on visually balancing art in a mat is to keep your bottom mat border equal to or larger than the side and top mat borders. Visually support the art!
Study the balance of the borders in the examples above. The artwork in each diagram is exactly the same size, yet each mat design creates a different feel on all of them. Also, keep in mind that each piece of art has its own unique visual, textural and compositional qualities. The approach to balance will vary per piece.
Finally, don't be skimpy on the mats. A wide border gives the eye transition from the frame to the art, allowing the eye to rest before it reads the art. A mat border can be too small, but never too big ~ in my opinion.
Remember, artists are in the business of the visual arts and are selling to visual people. How the artwork is finally framed can determine a successful sale in a gallery or the presence in a room.