Free Camera Lucida

How to trace images and live video feeds using free software and your smartphone and PC cameras

Red Onion (2021)

I was having trouble with my drawing skill, which was holding back my ability to complete paintings. And so I looked into computer-aided shortcuts.

I don’t consider it cheating, first because I was open about my process to the point of giving an in-class demo, and second because the way to learn a difficult skill is to break it down into constituent parts.

Here’s a painting by Valenciennes.

Pierre-Henri de Valenciennes. Bâtiments de ferme à la Villa Farnèse, les deux peupliers (1780).

I did a drawing of the Valenciennes, and uploaded it to an appropriately-titled website: https://www.whatswrongwithmydrawing.com/

What’s wrong with my drawing? Side-by-side comparisons.

As a value study, it’s not too bad, which means that I was making progress on that particular skill. But the drawing itself was off, and the website lets you see exactly where, using comparison lines placed on landmarks on the source and on your drawing. As you can see, the foreground is too large, the trees are too compressed and slanted, and the roofline silhouette is imprecisely drawn.

Checking your work is impeccable pedagogy. You’re doing it on your own, and then only using technology to measure accuracy.

But what if you could shorten the review cycle? What if you could evaluate, in real time, every mark you make on the canvas?

I figured out how with my second attempt at the drawing.

Sketch of value study for Valenciennes painting

That looks much better, doesn’t it? The trees look the right size, the composition is accurate. But how accurate is it really?

Overlaying a transparency of original painting on top of the drawing.

Precise contour match between the original and the drawing

Here’s how I did it:

The task was to overlay a transparency of live video of the canvas on top of the still image of the source photo, and then adjust the position and transparency of each.

The open-source Open Broadcaster Software OBS Studio essentially works as a video mixer. You can combine multiple sources, connecting to your laptop camera, an external device, or an application window.

The result is that you can see both images, video feed and still image, one superimposed as a transparency on the other.

At the beginning, it’s just the onion from the source image. Then, whenever you place a mark on the canvas or paper, you can watch the monitor to see your hand placing that mark exactly where it belongs. You’re drawing on the paper, but you’re looking at the screen.

You can use this technique to copy a source image onto a canvas, or you can take it step further by putting a camera in front of the still-life setup. This means you have two live video feeds: one for the canvas, and one for the still-life setup itself. With this approach, you can mess around with a 3-D still-life setup until it looks good on a 2-D canvas, without thumbnail drawings.

Our class had been working on a project to insert our own still-life objects into a master copy of a landscape painting. In my case, I wanted to add a new condo building in front of the Villa Farnèse in Valenciennes’ painting.

With OBS, it was easy enough to add another camera feed from my smartphone. I’m sure there are dozens of ways to do this, but I went with Zoom. I started a Zoom meeting from the PC, and used OBS to capture the video from the Zoom application. Then, I dialed into the meeting with the phone (turning off audio). With the phone on a tripod, I could then position the phone with a straight-on view of the still-life setup.  

I adjusted the camera height until the perspective looked right. 

I had the block just where I wanted it.

The next step was to trace the outline and key landmarks of the still-life object onto the drawing. Again, you’re looking at the screen, tracing an object that’s entirely out of view, while moving your hand on the canvas off to the side. 

And there you have it, The Poplars Luxury Condominiums at Villa Farnèse.

I know it’s a bit complicated, and I’ll have to shoot a YouTube video to do this explanation justice. In the meantime, if you want to try out something easier, it turns out there are all sorts of “camera lucida” apps for sale in the various app stores, and some of them look really slick.

But my approach has the advantages of price (free) and scalability (unlimited). You can do much more than just copy a still image, and by adding as many cameras as you want, you can do all sorts of things you could never do with a single camera.

Give it a try, and have fun!

And share your work! 

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