I have been shooting a lot with film this past year for my personal work and one of my favorite things to have fun with is double exposures. I had already been playing a bit with digital double exposures with the Canon 5D Mark III, inspired by the work of Sara K. Byrne (see her terrific tutorial on how she does it here). Shooting double exposures on digital, especially with the Mark III, is great for being able to see what you're getting right away, which on a wedding day for example, is a nice benefit. With film, while you can still pre-visualize things a bit, there is an element of surprise involved, not always knowing exactly what you are going to get, and that is just one of the many things I love about shooting film.
Some film cameras have a double exposure function built in (Nikon FE2 and FM3A for example), allowing you take one frame and then take another one directly afterwards, before advancing to the next frame. This is a fun thing to try if you have multiple scenes in front of you that you want to combine (i.e. a person and background you like).
The technique I used on most of these images here however is a bit different. I first learned of this method from one of my favorite film photographers, Ryan Muirhead (@ryanmuirhead on IG), who in turn credited learning this from someone else. This method has essentially been around as long as 35mm film has and is just as simple. Basically, shoot an entire roll of the "background" images first, rewind the film, and then reload it for a second round (in my case, portraits) later.
One advantage to doing it this way is, if you find yourself out and about somewhere cool and feel inspired, you can shoot a roll of the backgrounds and then save the roll(s) for when you have a person or subject that you want to overlay them with later. I have rolls saved up at home labeled with stickers that tell me what is on them (Maui skies, raindrops, San Francisco cityscapes, bokeh, etc) so that I can use them when the double exposure mood strikes. You can just as easily shoot the portraits first and the backgrounds later. What's also cool about this method is that you don't have to use the same camera for each round, most any 35mm camera will work, which means you can take the first round with one camera/lens and the second round with a different camera/lens.
Regarding exposure, the most important thing is to simply under-expose each shot by one stop or so (-1). Since the film is getting exposed to light twice, you need to darken each image a bit so things balance out in the end. This same formula applies to digital as well. There are a number of ways to do this. The easiest way for me is to simply shoot in Aperture Priority mode and set the exposure compensation to -1. On a more automated camera like the Nikon F6, for example, I sometimes dial it in to -1.3 or -1.7 if the scene I am shooting is particularly bright (i.e. bright clouds in the sky). For triple exposures or more, you just want to darken things even more, -2 or -3, respectively. Using a professional lab for your developing and scanning (I use and highly recommend Indie Film Lab) can also go a long way towards your final shots looking as best they can.
On a camera without an exposure compensation option (i.e. Leica's), you can simply set the ISO so that your camera is under exposing by a stop. For example, if you put in 400 speed film, set the ISO on the camera to 800 and then just meter/shoot normally based on the aperture you choose. The shutter speed your camera would have fired at, i.e. 1/125 of a second, will now be 1/250th of a second. In a nutshell, faster shutter speed = darker image. For older all-manual cameras without Aperture Priority, you just need to use a meter of some kind, either the one in camera or a hand held type.
Another important tip if you are going to reload the film is to make sure when you rewind the film, that you don't rewind the film all the way back in to the canister so that you can reload it. On any manual winder like the M6, Nikon FE2, or Canon AE-1, just rewind softly until you hear that soft click at the end and then stop. Open the camera and the leader should be out, similar to a new roll. On an auto-winder like the F6, there's often an option to manual wind still, and with the F6, there is also a setting in the custom functions to leave the film leader out after auto-winding, which is what I do.
One tricky aspect to note when shooting this method, and one I am still learning to work around, is that the film does not always start at the same point when you reload the film and sometimes this can lead to the frames being misaligned when you shoot the second round. You can see this in some of the images below, a vertical band going through the image. This is essentially one image in the middle with two different frames on each side of the band. Sometimes, this means the band going right through the subjects face for example. Not something I am going for, but can yield some fun and interesting results none-the-less.
Learning how the dark and light parts of images overlay in double exposures takes some time. Essentially the dark areas of the image will overlap, and the brighter highlights will generally not. For the portrait of Christina in the next shot below, I shot in the middle of the afternoon in my garage, with the garage door open and her facing outside, with a black backdrop behind her. The soft indirect light from outside provided light to her eyes and face, and the dark background allowed the image of a crashing wave in Maui to be seen on either side of her.
It can help to pre-visualize this at times but usually I am just as excited not knowing how things will turn out, especially when you don't know exactly what you are overlaying on each frame. In the end, my best tip is to just experiment. Combine wide-angles with macro shots, in-focus shots with out of focus shots, long exposures with short ones. Possibilities are truly endless.
The last step for me is sending my film to get developed and scanned by the good folk at Indie Film Lab. They work wonders. A few weeks later, I receive my scans and see the results. And for me, that is terrifically fun. Hope this helps a bit and encourages you to go out and try some double exposures on film yourself!
Here are a few of my personal faves. Big thanks to all of the friends and models who helped create them with me.