This is an easy-to-make functional camera that shoots brilliant blue photos on cyanotype paper, which is historically used to make blueprints. It's also my entry in Instructables' Annual 'Colors of the Rainbow' contest, in the category 'Blue'!.

While wandering through a 100-yen store in San Francisco's Japantown a few weeks ago, I spotted a shelf full of black cardboard "sliding drawer" boxes.

The boxes instantly reminded me of a vintage Kodak Brownie box camera that I had bought from a thrift store just a few days before. I had taken the box camera apart as soon as I got home, and marveled at how simple a device it was-- all you really need to make a camera, it turns out, is a box with a hole in it; some sort of light sensitive paper (film); and a lens (though you can even do without the lens if you're making a pinhole camera).

Well, here was a box. On a hunch, I walked a few aisles further and found what I was looking for: a small selection of magnifying glasses. Magnifying glasses, as double convex lenses, are suitable for creating images, and therefore make fine camera lenses.

That's two out of the three components you need to build a camera from scratch-- available for a grand total of $2.50. I bought the box and the lens, then started thinking about how I might secure the third component for a homemade camera: photosensitive paper. As it happens, I had recently been experimenting with the cyanotype process for making old-fashioned blueprints. Back before the days of modern CAD, engineering drawings were replicated by coating a blank sheet with a mixture of iron compounds (Potassium ferricyanide and Ferric ammonium citrate), laying a transparent negative above it, then exposing the negative to ultraviolet light. This process produces on the blank sheets perfect copies of the images printed on the negatives, with the caveat being that the copies come in a brilliant blue-- this is where the term "blueprint" comes from, and it's why a lot of engineering and architectural drawings from before the 1940s have that striking color scheme.

Today, cyanotypes are usually used in an arts and crafts context, to make sun prints from plants and photo negatives, and you can buy the requisite chemicals in many craft stores as a set for $10-20 USD. I wondered whether I could take photographs directly on cyanotype-coated paper, since even though it uses iron compounds instead of silver compounds, it's basically the same thing as film.Turns out, it works! You can take photos directly on cyanotype-coated paper, no development process or chemical baths necessary. I was immensely happy with my results; here's how you can do the same thing I did...

Supplies

Cardboard box, preferably DAISO Drawer Box - Black, 3.94 x 3.94 x 3.15 in
Any small magnifying glass, I used DAISO Magnifying Lens - Mini
Any loose cardboard, I used some thin non-corrugated stuff I had lying around.
Cyanotype Parts A & B, I used the Bearly Art Cyanotype Parts A & B
Eye Droppers (2)
Foam Brush (Optional, but optimal)
Watercolor Paper (I bought a big pad for $4 at Michael's)
Glue
Masking tape

Step 1: Mount Your Lens

If you have a traditional magnifying glass (lens and handle), then depending on how it's assembled, you can either pop out the lens or snap off the handle. This will leave you with only the circular lens.

Now, secure the lens to the inside of the box, lined up with the existing hole, using glue. Don't worry if the lens is much larger than the hole; as long as it fits inside the box, and you can align the center of your lens with the center of the hole, you'll be fine. In the next step, we'll find the lens' focal point and build a simple screen inside the camera.

Since my local DAISO only had a handheld reading lens in stock, I used that and built a fancy little cardboard carriage for it. Anything works, as long as it holds the lens parallel to and aligned with the box's existing hole.

Step 2: Find Your Focus

First three images above: a screen precisely the right distance from the lens, resulting in a crisp, focused image; a screen slightly too far away from the lens, resulting in a blurry image; a screen slightly too close to the lens, resulting in a blurry image.

Find a dimly lit room with a window, desk lamp, or other point light source to make this step easier. With your lens firmly secured in the drawer-half of the box (as per the previous step), point the hole toward the light source. You should see a fuzzy image appear on the far end of the box.

Take a piece of paper and hold it parallel to the projected image. This is your test screen. Move it slowly toward the lens; you should see the image become more sharp. At a certain point, moving the screen any closer to the lens will start to make the image blurry again. Go back to the distance from the lens where your image is sharpest, and make a note of this distance. This is how far away you'll need to build your screen.

Here's a video I made to roughly demonstrate what I describe in the paragraph above.

Building the screen is a pretty simple process; all you need is cardboard and glue. I cut a cardboard rectangle to the same size as the base of the box, then another about the height of the box, and glued the second perpendicular to the first at the distance from the lens noted in the previous step. I added some smaller pieces for support, and ribbon to help me pull the assembly out of the box (though the latter proved to be unnecessary).

Step 3: Make Your Cyanotype "Film"

To make the photosensitive paper we'll be using in lieu of film, gather your watercolor paper, cyanotype chemicals, eyedroppers, foam brush, a pair of scissors, and some sort of basic mixing palette (a bottlecap would work fine). The cyanotype process has been described in great detail elsewhere, and the process of preparing a sheet to shoot phorographs on is no different than the process of preparing a sheet to do sun prints on. I'll describe the technique I use briefly here.

Mix cyanotype parts A and B in equal parts using the eyedroppers. A single drop of each chemical should be sufficient to make 1-2 pieces of film.
Paint the mixture evenly onto a corner of the watercolor paper.
Place the paper in a perfectly dark place (closet, drawer, sealed box, etc.) for at least fifteen minutes.
Cut one or several square "film sheets" from the prepared corner.

That's all there is to it! We now have one or several small pieces of custom cyanotype "sheet film". I usually secure a piece to my screen (yellow side facing out toward the world) with some small pieces of painter's tape.

Step 4: Take Photos!

Now all that's left is to point the camera towards a light source to double check that an image is projected where we placed the paper, then close the box and point it at an image we hope to capture! Usually it takes at least 45 minutes to get an image on a sunny day. Since cyanotype is sensitive to ultraviolet light, outdoor light is usually preferable. There's no need to develop the sheets once you've shot on them-- they'll come out done and a beautiful blue.

Technically, the brilliant blue image you pull out of the camera is a 'negative'-- darks are light, and lights are dark. There's no non-digital way to 'invert' the image to more closely align with reality, although I like to snap a digital picture then invert it in Photoshop or a similar program (Lunapic is actually easier for this task, not to mention free and online!). The resulting image is a haunting sepia and cyan... I'll upload more in the coming weeks as I take them.