Silverbased

Lately I’ve been telling everyone I talk to about my newfound, bittersweet fascination with Polaroids. It’s like learning that a loved one has a terminal illness—you want to savor as much of your remaining time together as you can.

As I understand it, the factory production lines for Polaroid film have actually stopped; what’s left is a few months’ supply still in the distribution pipeline. So I’ve been buying up Polaroid 600 packs whenever I come across them. (The best prices I’ve found are at Office Depot online; and locally—brrrr—at Walmart.)

But to stretch those last remaining shots, what better idea than to expose each frame more than once?

Most of the peel-apart packfilm cameras allow double exposures easily; and there is a known technique to trick Spectra cameras into shooting them. But for 600 film cameras, the only method I have learned about seemed complex and inconvenient.

But today I have a nifty camera mod which permits double exposures on 600 film—an inspired idea by my friend Allison Stanley. She owns a well-used Polaroid One600 camera, which sometimes failed to eject prints correctly. Appreciating the quirky beauty of her overlapping exposures, she suggested wiring in a “kill switch” to disable the print-eject motor at will.

I thought that idea was pure genius, and immediately wanted to try it out. It turns out that there’s a slight complication: All the 600 cameras I experimented with use the feed motor to recock the shutter too. But still, after adding the switch, a workable technique for 600-film double exposures does become possible.

Opening Up the Camera

The Polaroid One Step shown here is a typical 600 film model—easy to find for a few dollars at the thrift store etc. And this gray body-style with its flip-up flash is particularly easy to open: Its plastic shell simply snaps together. Let’s look.

Start by taking the flip-up flash and holding at about a 45-degree angle as shown. At this angle, it is possible to gently flex the side ears of the flash outwards and pop them free from the the camera body.

Lay the flash back on the top of the camera, out of the way as you remove the front panel. (But try not to put too much strain on that delicate ribbon cable as you go through the following steps.)

The front of the camera simply snaps into place; carefully insert a prying tool at the points shown by my knife and the red arrow; then ease the camera faceplate free. (The shutter button parts will fall out loose, so work over a towel or a tray so nothing gets lost.)

Here’s the opened camera, with the shutter-button assembly at left and the removed front panel at right.

Locate the ribbon cable which connects to the motor at the front of the camera. The conductors I’m pointing to are the ones that provide electricity to the motor. All we need to do is to cut through one wire and route it through an external switch, and the camera’s film-eject motor can be disabled as desired.

One flaw of that gray One Step above is that its electronic flash fires with every shot. Especially for double-exposures, I preferred not to risk washed-out colors by always using flash; instead I made the kill-switch mod to a vintage “rainbow” OneStep600 instead. But its disassembly needs a few extra steps. If you want to modify one of these, see the details here, then return for the other steps below.

Make the Hack

With small scissors cut through one of the conductors of the ribbon cable (the left side gives you more length of wire to work with). Then slice the clear plastic between conductors so you can pull the free cut ends outwards.

Prepare a small switch by soldering about 3 inches of wire to it. The type of switch isn’t important; but for ease of remembering I’d suggest orienting it so the contacts close when the switch is moved towards the front of the camera.

Drill a small hole in the side of the camera, into the hollow space under the photocell assembly. Thread the switch wires through this hole. Be sure to locate the hole far enough back so that the camera’s front panel can be replaced without interfering.

You could do a neater job than I did by mounting the switch inside the camera body; but I actually preferred mounting it in a sideways orientation where it would be less likely to get snagged and flipped accidentally. I glued the switch into place with hot-melt glue, adding an extra blob on the bottom to cover and insulate the solder tabs.

Cut back any excess length of the two wires, and solder their ends to the cut motor ribbon cable. The ribbon seems to be tinned already, so I found soldering to it surprisingly easy; but you do need to avoid jiggling the wires while the molten solder cools. (Forceps, etc. could be useful here to hold wires steady.)

That’s it!

Now it’s time to put the camera’s front back on. Be sure the lighter/darker control is centered so it will engage with the internal slider properly. I think it’s easiest to reinstall the shutter button parts by tucking them into the recess on the camera’s front, then sliding all the parts back into place as a unit:

Re-attach the flash pivots (again holding it at a 45° angle) and the camera is ready to use.

Using the Modded Camera

Okay, we’ll assume you’ve wired the switch so that when flipped forwards, the contacts are closed. In this position the camera operates exactly as originally.

Keep the switch “on,” and load a fresh film pack. When you close the door, the black cover sheet should eject. (If it doesn’t, something is wrong: Re-check your work.)

Remember, after every exposure the motor needs to run sometime, to re-cock the shutter and prepare for the next shot. But the switch allows us to delay that, and not have the print spit out immediately.

So the technique for double exposures is this:

• Flip the switch backwards, and make your first exposure (shutter fires, but print does not eject). I’d suggest that you slide the lighter-darker control all the way to darker for your first tests.

• Drop the film door open; then flip the switch forward (the motor immediately runs; but the rollers are disengaged so the print stays inside the pack)

• The front edge of the print (or as shown here, two prints) is pushed out of the pack slightly. Carefully push these front edges back into the film pack, as far as you are able.

• Close the door, leave the switch forward, and make your second exposure (print ejects normally).

• A third exposure (etc.) is possible by repeating the same cycle:

Switch off/shoot/drop door/switch on/tuck print into pack/close door.

There’s a couple things to note about this method. One is that pushing the front edge of the print back into the pack in daylight can leak light into the pack: This gives the funny “row of teeth” pattern seen at the bottom of this shot:

You can minimize this, by delaying the door-drop maneuver until you can move into dim light (or, push the print edge back into the pack by feel, with a jacket etc. thrown over the camera). But I’ve actually grown rather fond of this quirk.

The other issue is a general one for double-exposures: You can only add light, not subtract it. Any brightly-lit area of your subject tends to override the image in the other exposure. It’s mainly in the darker areas of the scene where you’ll see the double-ness of the exposure. So try to include sufficient dark, blank areas in your shots. And stick to simple, bold subjects until you get the hang of how images combine.

These are strange days, when the cost of a complete Polaroid camera is trivial compared to the preciousness of each exposure. Yet the freedom to cut up and re-jigger old cameras is liberating, too. And the magical serendipity of Polaroid doubles seems like a fine way to celebrate our farewell to this unique and irreplaceable medium.

Important Update: with most 600 cameras, making double-exposures will confuse the frame counter. After making 10 exposures (not after ejecting 10 prints) the shutter button will lock.

The slightly-inconvenient cure is this: grab a spare black film-pack cover sheet and go into a dark room. Open the camera, remove the film pack entirely, and slip the black sheet back into the top of the film pack. (Orient the little dangly plastic tag towards the cut-away corner of the pack.) Close the film door, and allow the camera to spit out the black sheet again (flip on the kill-switch if needed). The frame counter will be reset and you may continue taking pictures.

Today’s post is for folks who are just getting interested in pinhole photography—whether you’ve heard about it as a fun DIY project, or as a creative technique for producing evocative, dreamlike images.

Pinhole camera designs can be incredibly varied. The traditional scout-troop model was built from a Quaker Oats carton, exposing a single sheet of photo paper. But “single shot” pinholes are a bit inconvenient, especially as fewer people have access to a darkroom these days.

So lately I’ve been emphasizing pinhole designs using roll film—like my plasti-pinhole project and it’s siamese twin variant. (I also designed a 120-film camera for shooting 6×12 panoramas, a project you can find in the Best of Make book.)

Pinhole image on Fuji Acros 120 film, taken with a converted 1950s Argus 75 camera

But I’d like to give a little background that applies to all pinhole cameras, of any form. Then we’ll look at a method for fabricating the all-important pinhole itself.

Some Theory

So why does a pinhole camera work? Imagine a light-tight box, with a piece of film on one side and a tiny hole in the other. Each point on the film can only “see” one patch of the outside world, the one lined up with the pinhole—whether it’s light, dark, blue, red, etc. So an image of the scene forms upside down on the film.

With that idea in mind, visualize what happens if you move the pinhole closer: The angle from the film corners to the pinhole gets more oblique, and the camera takes in a wider view of the outside world.

In fact, the distance between the pinhole and the film is exactly equivalent to the focal length of a lens with the same coverage. Hence, it’s most informative to measure pinhole “focal lengths” in millimeters, just as with lenses. (Because a pinhole does not actually focus light, using focal length in this sense is technically a misnomer—but that’s the way most pinhole enthusiasts refer to it.)

So How Large is a “Pin” Hole, Anyway?

Up to a certain point, the smaller the hole you use, the sharper the image you get. But if you go too small, you run into a problem with diffraction—the tendency of light waves to fan outwards when they graze the edge of an obstruction (it’s a problem for lenses, too).

Thus, there is one hole diameter for any given focal length which gives the optimum possible sharpness. Historically, a number of great scientific minds labored to derive the proper formula to compute this. But today, you can just put your faith in a handy online calculator, like this one from Mr. Pinhole.

For typical cameras the best diameter works out somewhere between 0.2 to 0.5 millimeters—equivalent to an f/stop of f/100 to f/300. This definitely implies some long exposure times might be needed. But everything from infinity to inches away will be recorded with equal sharpness.

If you want a camera covering a particular angle of view, you have a choice between using a small piece of film with a short focal length, or building your camera using a bigger image format and a longer focal length. For example, a 30mm focal length on a standard 35mm film frame gives the same coverage as a 225mm focal length exposing an 8×10″ sheet (both show about 72° diagonally). But which is better?

As it turns out, the optimum pinhole diameter scales up more slowly than the focal length: The bigger you build the camera, the smaller the resulting f/stop, and the sharper the image. But eventually, ever-larger image formats can become cumbersome, costly, and impractical. (And besides, if it’s more sharpness you want—you could always use a lens!)

My own conclusion is that 120-film pinhole cameras offer a good trade-off between image quality and film-handling convenience.

How Do I Make a Pinhole?

The goal in fabricating a pinhole is to get one that is nicely circular, without ragged edges, and whose diameter you have at least roughly measured.

You’ll probably do best by piercing your hole in the thinnest possible material. If your pinhole more resembles a microscopic “tunnel,” oblique light rays will be blocked and you’ll get noticeable vignetting. While that effect can be interesting to explore, you’ll likely also see problems from light reflecting off the inner walls of the hole, degrading contrast.

While it’s fine to experiment with tinfoil or the side of a beer can, I settled on a method for fabricating pinholes in aluminum roof flashing (about 0.01″ to 0.02″ thick). I just find it more secure to fasten those flat, stiff sheets into whatever camera I’m building.

First, start by cutting squares of metal 50mm on a side. Why 50mm? Because it’s the same size as a 35mm slide mount—this may come in handy when it’s time to measure the pinhole diameter. Cut several extras, since there’s often a bit of trial and error in achieving your target pinhole diameter.

Place the metal square onto a piece of softwood, and tap a small dimple into the center. A ball-peen hammer works fine; however it might be easier to center the dimple if you hold something like the rounded head of a carriage bolt against the metal, then strike that with the hammer.

The dimple only needs to be high enough that you can selectively rub that spot against a sheet of sandpaper to thin it.

Press and sand the bump against fine sandpaper—320 or 400 grit works well. Here I show the sandpaper wrapped around a block of wood, to make it easier to hang onto; flexing the edges of the metal backwards will help avoid sandpapering your fingertips!

You want to rub with enough pressure that you’re definitely removing metal, but not so aggressively that you sand right through. After a noticeable flat spot has formed, it’s time to start checking your progress.

Gently press the tip of a sewing needle against the hollow of the bump. You are not trying to push it through yet—hold the needle by the sides to avoid applying too much pressure.

What you are testing is whether the metal is thin enough so that the tip of the needle telegraphs a tiny raised point through to the other side. If not, go back to the sandpaper and rub a bit more, then test again.

With your first test, you probably left a small pin-prick in the metal. Keep placing the needle in the same spot after that, to avoid inadvertently forming multiple pinholes.

Once the metal is thin enough for the needle tip to deform it, you should see something like this:

Take a couple of light strokes against the sandpaper to flatten the raised point. Now hold the metal up to a strong light—it’s possible that a tiny hole will show through already. But in any case, you’re getting very close.

Press the bump against a firm backing, like a telephone book. Replace the needle tip into the pin-prick you started, then give firmer pressure, pushing on the end of the needle as shown. You are not trying to push the needle through the metal—the diameter of its shaft is much too large. With gentle pressure you’re just trying to to push the point of the needle through.

Once you “see daylight,” go back to the sandpaper and lightly sand away any rough edges around the hole. Take the tip of the needle and very gently spin it in the hole to help round off any irregularities. Blow through the hole to remove any dust from the sandpaper.

Now It’s time to check if your hole looks clean, round, and what its diameter is.

It’s not necessary to achieve insane precision with your pinhole size. If you have nothing handy but a 10x magnifying loupe and a millimeter ruler, you can sort of “eyeball” whether your hole looks like one third of a millimeter, or whatever. Remember that a hole as far off as 70% or 140% of the desired diameter only means one f/stop of under- or overexposure, respectively. (This is within the exposure latitude for many kinds of film.)

But there are two easy methods to get a more precise measurement: Either use a slide projector, or a scanner connected to your computer. Today far more people have access to scanners than still own slide projectors—so I’ll describe that method first:

Simply put the pinhole metal into the scanner, and scan at the highest available resolution. (Only scan a small selection around the hole itself, to avoid ridiculously bloated document sizes.) Either scanning the hole on a flatbed document scanner or with the slide holder of a film scanner is fine—although a film scanner may offer higher resolution.

Some photo-editing software has a ruler tool allowing you to measure sizes directly. But even in a more basic program (like the old version of Elements shown here), you can still measure the hole. Drag out a selection which just barely encloses its image; then open the “info” palette to read off the size.

A highly-magnified scan of the pinhole; the selection is 107 pixels square. There also appears to be some gunk clinging to the hole that should be cleaned out

To get the most accurate measurement, I suggest going into the preferences and changing the default units to pixels. If you scanned the hole at 9600 dpi, and your selection is 107 pixels across, its diameter equals 107 divided by 9600, or 0.0111 inches. There are 25.4 millimeters in an inch, so that pinhole size translates to 0.28mm.

Personally, I find there is a lot of trial and error in achieving at a nice clean pinhole of the correct diameter. So I will often make a batch of pinholes at the same time, to get one good one. In that case, the scanner method becomes a little time-consuming.

So to me it’s worth setting up an old slide projector with a manual feeder, where I can quickly slap pinholes in and out, and immediately see how they look. This allows me to start with a hole slightly undersize, then nudge its diameter larger (by gently spinning the needle tip in the hole), quickly rechecking until I hit the target size. (Sandwiching the pinhole into a spare cardboard slide mount makes it fit in the projector gate more snugly.)

The key thing is to know that the opening of a standard slide mount is about 23×34mm. From the height of a slide image projected onto the wall, you can calculate the magnification; and from that, you can figure out how large the spot of light would appear from a properly-sized pinhole.

But I have an even simpler trick: Move the projector back and forth until a complete slide is projected at a size of 46 by 68 inches. At that magnification, every inch of the projected image represents 0.5mm at the slide mount. Thus you can read off pinhole sizes very rapidly (a ruler divided into tenths of an inch is helpful).

Measuring the projected image of a pinhole

If you discover you went wildly over your target pinhole diameter, start over with a fresh piece of metal, but try to press more gently with the needle this time. And don’t throw away the “bad” pinhole. Just write its diameter onto the metal using a permanent marker, and hang onto it somewhere. Building pinhole cameras is rather addictive; a day may come when you create another one needing exactly that diameter hole.

Figuring pinhole exposure times means knowing the equivalent f/number. This is simply the focal length of your pinhole camera, divided by the pinhole diameter. (But both need to be expressed in the same units, whether millimeters or inches.) It’s preferable to avoid f/numbers under f/100, just because the correct exposure in full sun will be a fraction of a second—not something most homemade pinhole shutters can time accurately.

When you need to calculate exposure times, few light meters will indicate f/stops all the way into the hundreds! So it’s helpful to know that f/128, f/181, and f/256 are exactly 6, 7, and 8 stops smaller than f/16. Find the indicated exposure time at f/16 and count off the steps to the correct (longer) time needed for your pinhole exposure.

Have fun!