Often, we will take photos of things we might want to paint. And there are times when we want to do a ‘master copy’ at the same scale or ratio of the original but larger or smaller. The question has often come up, “How to I make something larger or smaller but at the same ratio of my reference material without resorting to a math equation?” Though there are others, I’m going to talk about 3 ways to scale your work.

The first way is to use a Proportional Scale. This tool is really simple as you line up the inner and outer ring to the original height and width, and then everywhere along where the lines line up will be an accurate scaled version of the original.

Just to the left you can see that 9 and 7 are clearly lined up. As you move your eye around the dials you will see where the lines line up. Some are very easy to see, such as 18 x 14, but anywhere along the circle will be an accurate scale of the original measurement you put in. The measurement of 2 ¾ x 3 ½ is also an accurate ratio of the original 9 x 7. I use my Proportional Scale a lot. From experience I can strongly suggest getting the largest version as possible unless you have a magnifying glass in hand as the numbers are rather small. That said, most modern cell phones have a magnifier built in.

Here are a couple of videos showing this great tool in use.

The first one https://www.youtube.com/watch?v=Mi_6u338yhU shows how a quilter might use this tool.

And how a painter might use it: https://www.youtube.com/watch?v=1OJQfEh3VrI

I use it as I described above and don’t really think about the percentage of change. However, if I was using a printer that is a very helpful piece of information indeed!!

Another way to scale an image is by using a diagonal line. Beginning at one corner and angling it to the opposite corner, any vertical and horizontal line that intersects the diagonal will be the same proportion as the original. Here is an image where I want to scale up. The photo is 4 x 6 and I want to make it larger:

Running the diagonal from opposite corners

Here you can see that I’ve placed horizontal and vertical lines that intersect the diagonal, thereby changing the size, but still keeping the scale of the image the same.

Now, what would happen if I wanted to do a painting or drawing but the canvas wasn’t the same ratio of the original? In that case I would crop the painting, either its height or width, or a bit of each, so I could keep the scale and still keep the painting’s composition. For example, in the Ernest Lawson “Springtime, Harlem River” painting below, the original size is 25 x 36.

 If I’m cutting canvas to size and scale there wouldn’t be a problem. But if I was using a standard sized canvas, I would have to make some decisions. A standard canvas size closest to the size of the original would be 24 x 36. If is lay out the image on a paper that is 24 x 36, I start the enlargement as I did above, from corner to diagonal corner. The image of the painting is under the corner with the arrow on the lower left.

As you can see, I will have a bit a space on the canvas that is outside the boundary of the painting. When this is the case, or the opposite, when there is more original painting than the canvas, you will have to make a decision as to how to crop or adjust the work. Either you can add some in the same style as what is painted to either the right or left side, or perhaps a bit on both sides. If there is more painting than canvas, then you will have to edit the original painting to account for the discrepancy. Again, you can take some off the top or bottom or both, or from the sides, whichever will give the most pleasing result while keeping the painting as ‘intact’ as possible. In truth, when you are making a copy, it’s not supposed to be exactly the same size as the original. (When making a copy that you want to sign, you should sign your name and then add, after Artist X.)

Once you’ve set your boundaries you might want to scale the objects inside the picture frame. You can do this using a tool that dates to DaVinci, and perhaps even further back in history, called a Proportional Divider.

A Divider can be used to get an overall measurement, but its real value is when you want to get accurate measurements within the picture plane, not getting the overall outside dimensions. With this tool you set your small scale to the original image or part of an image and then the opposite end, which is often wider, is set to the height or width you want. Once you get this proportion you set the screw. Once the screw or clip is set the widths of each end of the Divider are always in a direct relationship to each other no matter if you are measuring a smaller or larger area.

These dividers come in a variety of materials - metal, wood, and plastic, and at a variety of price points. Some have a locking clip and others have a screw such as this one from Jerry’s Artarama.  I have a couple of Proportional Dividers, one my son made for me which is rather large, and a smaller metal one like the one above on the left. The price points on these range from about $10 to over $150. But the cost absolutely doesn’t affect its accuracy. They all work by using a consistent ratio. The most important thing to remember when using this tool is that your arm MUST be straight, and you MUST measure from the same spot. (But you already know this as it’s the same for any kind of measuring.) Here is a YouTube video from Draw, Mix, Paint showing how to use a Proportional Divider.

Try the different methods and see which works best for you and let me know how it goes.