Silverbased

Projects and ponderings for film photographers

Archive for June, 2008


Sawing Expensive Glass In Half

A tip of the hat to friend Katrin for forwarding a great link to Wired’s gadget blog, with a look at some optics exhibits at the Deutsches Technikmuseum Berlin.

The museum shows several camera lenses cut open—one of which appears to be a Leica Tri-Elmar-M:

Leica Tri-Elmar-M, Bisected

I realize this museum is in Berlin, and thus wants to showcase Germany’s well-regarded optics industry. Still, it’s a bit heart-stopping to note that this particular Leica lens is now out of production, and was hardly an inexpensive item—one currently for sale on eBay has a “Buy It Now” price of USD $3,350!

This is an unusual lens for M-mount rangefinder cameras, that can be switched to 28, 35, or 50mm focal lengths. Note that it is not exactly a zoom lens, as only those three discrete focal lengths are available. (This makes sense on a rangefinder camera, where the viewfinder also switches between several discrete choices of frame lines.)

It’s actually rather impressive that the lens achieves this (and has a good reputation for sharpness to boot) with so few lens elements (8 elements in 6 groups).

If you were interested in my past post about simple camera-lens design, check out the link. The complexity that goes into sophisticated camera lenses can be pretty impressive.

Pimp My Polaroid, Part 3: Double-Exposures

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.

Pimp My Polaroid, Part II: SX-70

The collapsing Polaroid SX-70, introduced in the 1970s, may be one of the coolest cameras ever made—and it’s definitely my favorite Polaroid. So in our final few months before the company stops making film, I’m determined to get the maximum use out of mine.

Aside from a few price-gougers on eBay, there are no supplies remaining of the Time-Zero film packs created for the SX-70 cameras. However, there are many descriptions on the web of how to adapt a Polaroid SX-70 camera to use 600 film packs—even Polaroid has one.

Polaroid SX-70 camera adapted for 600 packs

The basic problem is that the original Time Zero film packs for the SX-70 had a speed of ISO 75; while 600 film has a speed of… well, 600. There are a couple of ways to solve this, and I won’t repeat all the information available elsewhere.

I wanted a solution that left the camera in unmodified, original condition, and didn’t rely on the “lighter/darker” dial for adjustment. The simplest answer is to add a 2-stop neutral-density filter over the lens. (Admittedly, this makes the viewfinder image rather dim.)

Originally I had high hopes for holding a regular Hoya screw-in polarizer in front of the lens: This cuts out about two stops, plus would have sometimes helped deepen colors by rotating it to different angles.

But it turned out to be a real fumble to hold the polarizer in the correct place; and worse, the image seemed a bit washed-out and greenish.

Flexible gelatin filters are a better choice: They can be taped permanently in place while allowing the camera to collapse normally. So I wanted to report success in adapting my SX-70 using filters taken from a swatchbook of Roscolux theatrical gels.

Swatch-book of Roscolux theatrical gels

You only need about 30mm square to cover an SX-70 lens. Perhaps some friendly theater tech will let you snip out what you need from their samples or scraps. I got my swatchbook by requesting it from a form on the Rosco website—but perhaps too many photographers were abusing this, because the page has vanished now (I blame Strobist readers!)

Roscolux filter samples have handy light-transmission info included right in the swatchbook. So it was an easy choice to start with #98 “Medium Grey,” which claimed 25% light transmission (that is exactly two stops). I found the exposure was almost perfect—perhaps just a shade light on my camera. However there was a slight greenish tinge to the image which bothered me a bit.

I tried sandwiching the gray filter with #3318, a pale magenta “1/8 Minusgreen.” That worked great, but still gave a slightly bluish color palette. Finally I tried the #98 gray plus #05, “Rose Tint.” This seemed like the best combination overall—slightly warmer grays but still neutral. Having said that, the color casts were pretty subtle and you might be happy with any of them.

Sample Polaroid 600 print from SX-70 camera

Polaroid 600 film shot in SX-70

The other issue with fitting 600 packs into an SX-70 is that there are four little plastic nubs on the bottom of the pack whose purpose is to stop you from sliding them into the “wrong” camera. It’s possible to use a stiff card to slip those over the obstructions in the SX-70’s film compartment; or even to force the pack into place by tipping it in at an angle.

Shaving nubs on Polaroid 600 pack to fit SX-70

But it’s no real problem to shave the nubs away with a sharp blade. According to Polaroid, it’s only the two middle nubs which hang up on the opening to the film chamber.

With these two mods, you can take that sleek SX-70, in all its folding, close-focusing grooviness, and put it back to use again!

[See another Polaroid project: the Pack-film Pinhole]

________

UPDATE: June 20, 2008

Thanks to Megan, commenting below, for noting that you can buy the Roscolux sample book for $4—good tip!

Contrary to the instructions widely posted on the Internet, my original silver SX-70 did not have a neutral density filter over its photocell; hence I needed a 2-stop filter over its lens for proper exposure (the Roscolux #98).

However I just snagged an SX-70 model 2 (in stylish cream & tan), and successfully modded it too. This camera did have a 1-stop ND filter over its photocell; removing it (see photos at the link above) allows you to get correct exposure with only a Rosco #97 ” Light Gray” gel over the lens.

Conveniently, the first gel in the Rosco sample book is a completely clear one. It’s much easier to cut a new cover for the photocell from this than from a brittle CD case as often suggested. Another bonus of this solution is that the viewfinder image becomes one stop brighter too.

I still found that sandwiching a #05 “Rose Tint” along with the gray gave a more neutral color balance; but I will continue experimenting.

Thus continues my bittersweet Polaroid love affair…