Multiple Exposure is exactly what it sounds like: merging multiple exposures together into a single frame. All of this is done in-camera. This has many applications behind it as well. For instance, you can use Multiple Exposure Mode (ME) to fake long exposures, smoothing water in the middle of the day. Let’s say you are out shooting a waterfall and you have an ND filter on your lens, but can only get 1/30s of a shutter speed, and the water still has too much distracting detail in it, taking away from the main subject of the image. A single exposure causes too much chaos, but your Neutral Density Filter is too weak to block more light, limiting your exposure times.
To counter this, you can go inside your camera menus and select ME mode. My camera, the Nikon D810 can shoot up to 10 frames in ME mode. Other models are limited to 3 shots, depending on what you are shooting with.
For Nikon users, you can go into your “shooting menu” which looks like a camera on the left hand side. Scroll down until you reach “Multiple Exposure” and move the selector to the right to see more options. Here you will see three options: “ON (Series), ON (single photo), OFF”
“ON (Series)” will allow you to capture ME’s every time you press the shutter release and continue doing so until you turn this setting off. Using this option, you can create star trails and have fewer overall frames, with each frame being a longer exposure than your camera would normally allow. Let me explain: one time I set my camera to “ON (series)” and selected 10 frames (my camera’s max). Each individual frame consisted of a 30 second exposure. 30 seconds times 10 frames is equal to 300 SECONDS or 5 MINUTES. Using ME mode to take a 5 minute exposure compiles all of the 10 frames and condenses it into a single photo. Once the 10 frames are complete, with the camera set to “ON (Series)” it will continue doing 5 minute exposures, automatically. Now, instead of having 350 frames to capture star trails, you can use ME ON (series) to take the same exposure time, using fewer overall frames, which in turn will be easier on your computer, post-processing.
*This can lead to small gaps in your star trails if there is a delay between exposures* Some software applications can fix these gaps, but it is one other tool in your arsenal to use if you are in a pinch.
“ON (Single)” captures as many frames you set in your settings, and will turn off ME mode once the session has been completed and the final image is merged into a single raw file. This setting is great to fake long exposures during the harsh daylight hours. If your ND is limiting your exposure times and you are not getting smooth water, you can shoot the same scene (using a tripod) with the same settings and the camera will blend those exposures together, creating the long exposure effect on the water. Let’s go back to the 1/30s exposure for shooting a waterfall, or some other water body. If you use ME and set the camera to take 3 shots, the end result will be an exposure of 0.1 seconds, which is way longer than 1/30s, giving a smoother effect. The more frames your camera is able to capture in ME mode, the longer shutter speeds you can acquire. Another example would be a base exposure of 1 second and setting up to shoot 5 exposures, will yield a 5 second exposure!
Either of these two settings allow for creative freedom and open up more options for you to experiment with.
Multiple Exposures can be used to show the motion of clouds over the period of a sunrise or sunset, for star trails, flowing water that has too many ripples, creating time stack photos (more on that later) and whatever else you can get creative with.
If you turn on ME ON “Series” be sure and turn it off when you want to take regular photos again, using a single exposure. One time I forgot I had the setting turned on and was capturing Multiple Exposures accidentally!