Sunday, January 4, 2015

Sight Size and Scaling hacks

On our recent vacation I came up with some attempted solutions to measuring apparent sizes and distances and transferring them to the art surface at a different scale. In my experience, this is somewhat confusing to do, and horrendously confusing to explain in words! I will try to get it across as clearly as I can.
The first thing I noticed when we got to our rental in Provincetown was the amazing afternoon light on the intricately detailed panorama of boats, buoys, and docks of MacMillan Pier across the water. I took this photo at the time.

When I went to paint it from life a day or so later, I realized it posed some problems. I decided to frame a small portion of the scene, including the two red boats on the left, but they were far away and their apparent size was very small. I wanted to get a sense of the intricate tracery of masts, ropes, and piers in my small sketch, so I would have to enlarge it on the paper to be at all doable.
I usually paint simpler scenes by eyeballing and adjusting as I go, and complex scenes by measuring and painting at sight size. In this case, sight size was too small; I would have to scale it up. I sometimes use the traditional thumb on pencil technique to measure and resize, but I've never really liked that too much, because my thumb is imprecise and it requires too much left brainy translation of visual measurements to numerical proportions and back again.
My next thought was to adapt the same proportional conversion method I used for doing perspective without vanishing points to measure and plot the key landmarks and salient features onto my sketch.
For that, I used a separate piece of paper or card stock to mark off distances on one side and a diagonal line from a corner to map points onto the adjacent side. The angle of the diagonal determined the proportional distance of the point from the corner, which I used to place points in perspective on the picture plane without need of vanishing points.
In this case, the same idea could be applied to scaling the sight size to the re-scaled or projected size according to a constant proportion. I would use the short side to measure the sight size and the long side to record the projected size, then transfer it to the paper.
One vital factor is that the measuring tool be kept at a constant distance from the eye. Fortunately I have the reticuLanyard to help with this. The eye-tool distance can be controlled by adjusting the lanyard, so I could hold up the short side of the card and make its apparent width equal the desired width of the finished picture, based on the composition I had selected using a ViewCatcher.
I interposed the ViewCatcher between my eye and the extended reticuLanyard to establish this dimension.

I used the back of a business card as my measuring tool. As the number of tick marks and lines increased it became confusing, so I assigned numbers to the more significant measurements.

and the picture:

I tried two other ways to apply this idea. One was to make the marks and do the conversions directly on the art work, and the other was to construct a device with adjustable gauges so you wouldn't have to make marks on it.

Here's the one with the marks on the paper, with an overlay to make it more clear. You can see that I didn't faithfully adhere to the original measurements - this because either the boats moved or the light changed, revealing details I'd missed at first. I'm not interested in photorealism, but I was glad to get a higher level of accuracy than I would have with thumb and pencil. The watercolor paper is a 4" X 6" postcard, so it was small enough to hold the short side up to measure sight sizes. I labeled them "RB" (red boat), "BB" (blue boat), etc. I then located the points on the long side. I could use the same scale for the vertical measurements as well; I just had to remember to scale them on the long side, then take that distance and transfer it back to the short side. The brown line for the height of the highest light pole is an example.

This all sounds very involved, and it does take a bit of doing to get it all set up. However, you only need to establish a few salient points - once you have those, you can judge sizes relative to marks you already have on the paper.

The other idea I tried was to use rubber bands or hair ties on a piece of cardboard as moveable markers. This would reduce the number of confusing pencil lines and be more reusable.

Here is a demo using the good old climbing structure back home:

1. Set up composition and framing. Here, I'm using a ViewCatcher. I added some presets for other formats, in this case the "golden rectangle" indicated by the Greek letter phi.

2. Using reticuLanyard to set the eye-measuring tool distance, mark the sight size of the long side of the frame with a rubber band or hair tie. It helps to use different colors for different functions. The left side, with the notch, is always the zero point.

3. With a second hair tie perpendicular to the first, mark the length of the long side of the art surface (or "canvas"). In this case I drew a golden rectangle frame on a sketchbook page.

4. Hook a hair tie in the notch and stretch it to intersect the corner made by the first two. Secure it with a paperclip or similar. Actually, the paperclip wasn't quite secure enough, so I think I'll go with a small binder clip. This is the diagonal or slope line.

5. Take a sight size reading - I'm measuring from the zero point to the left leg of the climbing structure - and mark with another hair tie (red). It will intersect the slope.

6. Use another hair tie to cross the intersection of the sight size line with the slope. Its intersection with the long side gives the relative horizontal position of the left leg on the canvas. Mark its position on the paper.

And there you have it!

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