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A Great Sketch Results in a Great Painting
How to use the Grid Method to Achieve
Accurate Shape and Perspective in Art

Failure to achieve accurate shape and perspective in a finished work of art is why many of us give-up and declare ourselves "non-artists." There's nothing worse for a student's artistic self-confidence than having a painting of a horse turn-out looking more like a dog.

Yet there is a simple method of ensuring that the finished work will have proper shape and perspective. Artists dating back to the ancient Egyptians knew of a technique to break down a painting into smaller "grids" to effectively divide the image they were painting into a number of smaller images, each of which has less detail than the whole. The "grid method" was even used by Leonardo Da Vinci in both his works and in teaching. Today the grid method is alive and well in many art schools, but the math that's required deters many would-be artists.

Basically, the grid method is nothing more than overlaying a grid onto an original image that you wish to paint, and then placing a matching grid pattern on your canvas. For example, if your original image is an 8" x 10" photograph, you could draw a one-inch grid onto the photograph to create a grid pattern with eighty squares (eight squares by ten squares). The original photograph or image is now divided nicely into eighty bite-sized pieces, each of which are much easier to sketch onto the canvas than the entire original (Fig. 1).

Gridding results in better artwork because each of the smaller squares gets sketched one at a time until the entire sketch is finished. Once the sketch is done, the student can then begin to paint, mixing paints as usual. But if the sketch isn't done well, the finished painting will be disappointing. Gridding allows the underlying sketch to almost perfectly match the original, which will result in a satisfying painting with perfect proportions and perspective.
Clearly this method is useful only when there is an original image to paint. An imagined scene or abstract concept is difficult to grid, obviously, since the artist is not working from an original image or photograph. But most beginning artists--and certainly art students--learn by painting from an original photo, and the gridding method is an amazing aid in this regard.

Once the grid has been placed on the original image, the next step is to draw a corresponding grid pattern on the canvas. If your canvas is the same size as your image, then the grid that you draw onto the canvas is just the same size grid that you created on the original photograph. However, if in our example we're using, say, a 16" x 20" canvas, then we need to do some simple algebra to get 80 squares onto this canvas. Taking the longest side first, divide the canvas size by the number of squares along that side on the original image to get the distance between grid lines. In our example, 20" divided by 10 squares = 2" per square (Fig. 2).

This may be the right distance to use between gridlines on the shorter side as well, but we'll have to do the same calculation first to see if a 2" grid pattern will fit along the shorter side. Remember, in our example we have to get at least eight squares along this shorter side. Let's see if it works. Divide 16" (the shorter side of the canvas) by 2" and you get eight. So a 2" grid pattern will fit perfectly on a 16" x 20" canvas when your original image is 8" x 10". This works perfectly because the aspect ratio of both the image and the canvas are the same. The aspect ratio is the short side divided by the long side, or in our examples 8/10 = 16/20 = 0.8. Obviously you could paint a 24" x 30" or a 32" x 40" canvas using 3" and 4" grid lines, respectively, and still have the math work-out. Again, this is because the aspect ratios of the shorter side to the longer side in each of these canvas sizes is 0.8.

Now it gets a little trickier when the aspect ratio (or shape) of your canvas is different than the aspect ratio of your original image. For example, if we're using the same 8" x 10" original but now we're going to paint a nice, large 30" x 40" canvas, you can see that the aspect ratio of the original, 0.8, does not equal the aspect ratio of the canvas, which is 30"/40" = 0.75. Now what?
We still would like to squeeze an 8 x 10 grid pattern within the 30" x 40" canvas, but we'll have some "left over" space at either the top or bottom. Since we've already gridded our photograph, changing the aspect ratio of the photo is not an option. (There are tools that allow you to "re-grid" your original; more information on these tools is below.)

Let's assume that our original image is in "landscape" orientation, where the longer sides are the top and bottom. Now the question is how do we best grid this 30" x 40" canvas so that the composition is relatively unchanged from the original image?

First, let's see which sides we'll have to squeeze the most. Dividing the longer40" side by 10 gives us an even 4" grid size. Dividing the shorter 30" side by 8 gives us 3.75". Thus we have to limit the grid pattern to 3.75" if we're going to squeeze an 8 x 10 grid pattern completely into a 30" x 40" canvas. So if we are limited to 3.75" along the longer dimension, 10 squares at 3.75" per square will yield 37.5". Subtracting 37.5" from 40" results in 2.5" of "left over" space, which we'll want to evenly divide between either side. So the 8 x 10 grid pattern in our example will fit snuggly into a 30" x 40" canvas with 1.25" of left over (or non-gridded) space on both the left and right sides (Fig. 3). It also helps to label the columns and rows of your grids with numbers and letters.

Now that we know how to grid our original image and canvas, it's time to sketch. The gridding method is excellent for teaching the concept "paint what you see, not what you think." Often the mind fools the eye into seeing something that's not there, and the painting suffers as a result. The grids allow the eye to see only what's in each square, and effectively blocks out the rest of the painting. It is often helpful, in fact, to cut out a single square in a piece of dark paper to place over the original image to physically block-out the other squares. This helps train the "artist's eye" in the student, an important skill as the student advances (Fig. 4).

When the sketch is finished, the student carefully erases the grid lines on the canvas, and may then begin to paint. At this point, regardless of the color selection, stroke, or type of paint, the resulting image will be in perfect shape and perspective as long as the student paints within the lines of the sketch. The result is a very satisfying painting.

There are several tools available to help artists with the more mundane (ie., mathematical) aspects of gridding, most notably the Paint-By-Grids line of products found at www.paintbygrids.com. The pre-gridded canvas in the Acrylic Kit from Paint-By-Grids use a water-soluble ink, so that when the sketch is done the student simply wipes away the grid lines with a wet sponge (the sketch remains intact). The grid pattern used on this 12 x 16 canvas matches the grid pattern used in their Paint-By-Grids software program (a free trial version is available for download at software). This program is particularly well-suited for digital images taken with, for example, a digital camera or downloaded from the web. If your original image is a physical photograph, the Paint-By-Grids GuideSet includes 15 "Image Guides," which are transparent overlays with the grid pattern, each in a different size ranging from 2" x 3" all the way up to 8" x 10". This allows you to place an Image Guide over your photo, adjust the positioning of the grid to get the best composition, and select a different size if necessary. This system eliminates the need to draw a grid on the original image, and allows you to adjust the position of the grid later.

While gridding has been around for quite some time, the math involved is often a determent to using grids. However, with some of the recent tools developed by Paint-By-Grids, the need to calculate the grid sizes is eliminated. While it's important for the student to understand the math behind the gridding method, it is not always necessary for them to actually do the calculations. Certainly this will open the door for many more art students to use the gridding method, which is one of the most effective methods of teaching art ever devised.