Magic Portrait Drawing Machine

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About: Hi - I am a British chap living in China. I have been building/adapting/improving/breaking stuff since I was very small and I love the opportunity to document and share some of this experience here.

How confident are you at drawing someone's portrait?

Don't worry! With this machine, a pencil, and a bit of patience you can draw anyone's portrait - you just trace their outline onto a piece of paper. It couldn't be simpler!

What is it?

This is essentially a camera obscura, but with a couple of modifications to turn it into an amazing drawing machine. It is derived from similar devices (for example the Victorian one shown above), except in our case the image is projected onto a piece of paper inside a light proof box.

I have made several of these for various events and clients and happy to share the design here.

I should just get in under the wire for the OPTICS COMPETITION. If you like it, it would be great if you could VOTE, thanks!

How Does it Work?

Light bouncing off the subject is reflected by the 45° mirror and down through a convex lens in a light proof box onto a piece of white paper. The user looks through the viewer into the box and traces what they see.

Step 1: Materials

This is quite a simple build and very cheap.

Main body:

As you can see from other photos on this post, I have constructed this design in the past from MDF and scrap cardboard boxes. This model is made from 7mm two ply cardboard sheets.

I have a stock of 7mm sheets that are 1metre² , and two of these is more than enough.

You will also need:

Glue gun and several rounds of sticks

Paper tape to make the hinge and to make your cardboard joints neat.

Matt black paint (acrylic, or whatever you have lying around)

Some flexible lightproof material to seal the arm-holes e.g. thick fabric, black felt, serge. I used some foam material that I had lying around.

The special ingredients are detailed below. These are needed to make the Magic Drawing Machine come to life.

1. Convex Lens approx 100mm diameter, focal length approx 300-350mm. The photo above is from the online vendor from which I have bought lenses. These are very cheap here in China, but a quick search on ebay shows that they are readily available and fairly cheap elsewhere. They are sold as school educational equipment. The lenses I have used are glass, but acrylic would work just as well.

2. Plain Mirror. Just a normal mirror. Size is not crucial, but should be squarish, somewhere between 120mm and 180mm along each side. Again, ebay is your friend here if you don't have anything suitable lying around. I have found glass to be the best here, although acrylic could work, but the mirror surface must be perfectly flat. I have tried reflective plastic material and it doesn't work.

Step 2: Work Out Your Optics and Then the Size of Your Drawing Machine

First of all we need to work out the optics.

Assuming you have a similar lens to the ones I have used, you can use the dimensions on this drawing. If your lens differs, you will need to alter the geometry accordingly.

In most examples of this kind of drawing machine, the user is drawing a landscape or building, where the light rays are effectively parallel. We want to draw a portrait, so our subject is quite close, and the light they reflect will need to be carefully focused. Therefore we need our subject to sit an exact distance away from the mirror in order to focus their image inside our machine.

If you don't know the focal length of your lens you can experiment to find the correct geometry. You want your subject sitting around 1m away and their image focused onto the paper inside your drawing machine.

Step 3: Cut Out Your Card

For this build I am using virgin corrugated cardboard because it needs to be neat for the application I have, but better to use old card where possible.

If you have a cardboard box of a suitable size, it is also possible to adapt this (see images of drawing machine made from cardboard box, above)

As long as the geometry is approximately correct, you can fine tune the optics during the build.

Step 4: Assemble the Cardboard Pieces and Make Light Proof

After cutting out your pieces, check that they fit together and then start assembling using the glue gun.

The viewfinder panel needs to be hinged in order to lift it up to get your hands, pen and paper inside.

Make the hinge with some tape. I used paper tape, but whatever you have.

Paint the inside of the box with matt black paint.

Step 5: Install Lens, Mirror and Distance Gauge

The lens fits into the 100mm cut out in the top panel.

The mirror is installed at a 45° angle above this.

If you are unsure about the optics, use some tape to install first and test.

The distance gauge is a piece of rope or fabric tape attached to the front of the box. It allows the subject to check that they are exactly the right distance from the mirror.

In this case it is about 90cm, but you will need to tune yours.

To work out the exact focus distance, point a bright light at the lens. Move the Drawing Machine (or lamp) backwards and forwards until you see a sharp image projected on a piece of paper inside the box.

Cut your distance gauge to this length.

You should also install some stiff light proof material around the arm holes to minimise the light entering the box. This will help keep your image as bright as possible.

Step 6: Draw!!

Now you are ready to draw.

This is a fun experience for kids and adults.

You need to seat your subject exactly the right distance from the mirror (use the distance gauge).

This focus has a VERY shallow depth of field.

Pop a piece of paper into the drawing machine.

Get out your pencil, look through the viewfinder and wait for your eyes to adjust to the dim light. You should see your subject's image projected on your paper.

Oh, yes. It's upside down. Did I forget to mention that?

The drawing process involves tracing the image projected on the paper - what could be simpler?

Actually it isn't that easy (see above!). You can get some good results, but it does take a bit of practice.

It is difficult to see what you have drawn so you just have to go for it. A lot of the fun is in the 'reveal' and there is no embarrassment in making a very odd portrait. They all retain some charm.

Tips:

First of all you want your subject to be well illuminated so that you can see a bright image on the paper.

You can go outside if it is sunny, or direct a spotlight at the subject.

Secondly, you need to develop a very quick technique. If your subject moves, you will find it difficult to fill in the parts you missed. Ask your subject to sit very still and try to capture them in less than a minute.

Maybe I will make another instructable on how to quickly trace a portrait!

Optics Contest

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Optics Contest

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    5 Discussions

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    Gannburg

    12 days ago

    Great Instructable! I've been drawing with a camera obscura for a few years now and this design makes mine look like 16th Century!

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    DennisO22

    13 days ago

    Great instructable. Do you have a design for a Camera Lucida?

    1 reply
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    hugheswhoDennisO22

    Reply 12 days ago

    Not yet - that is something I might look at in the future, although first I want to work on the technique for using this device effectively - i.e. how to blindly trace a portrait in just a few seconds.

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    Kink Jarfold

    14 days ago on Step 6

    Next is the Camera Obscura, right? Great Instructable. --Kink--