[Mike McCarty]

Let's say you have a photo which is 8" x 10", a size large enough to read and commonly printed by photo processors or on your home printer. Let's say then that you want your painting to be 20" x 25". Your painting in this case is 2.5 times the size of your reference. The photo could be any size large enough to read and the painting, theoretically, could be any size up or down from that.

Pick a point on your reference, say the inside corner of the right eye, measure the distance in from the left side of the edge of the photo. Multiply that distance by 2.5 times and make an approximate (up or down) "light" mark on your canvas at that point. Then measure from the top of the photo again to the inside corner of the right eye. Multiply that measure by 2.5 then make that mark in conjunction with the previous light mark. You now know precisely where the corner of the right eye will be on your expanded (whatever sized) canvas.

You make a few more marks, edge of the mouth, tip of the nose etc, etc., and before long you have enough to sketch the balance.

Good thing is, no matter how much paint you put on the canvas, you can always get back to that perfect spot which is the inside corner of the right eye, or, the outside edge of the left cheek, or, whatever.

I think you could go from an 8x8, 8x10, 8x12, whatever your composition may be, as long as it's large enough to easily read and handle, to a billboard using this method.