By Mark Fuller
A double (or multiple) exposure is when two or more images are combined into a single image. Although this creative technique is most popular in above-water photography, using it underwater can produce some truly special results.
In the days of film, this effect was achieved by a lever disengaging the advance mechanism, allowing the shutter to re-cock without advancing the film, thus allowing a second, third, etc., exposure on the same frame of film. These days, most SLRs -and even some point and shoot cameras- have an image overlay and/or multiple exposure settings, allowing a far less technical method to achieve the same affect (check your user manual).
You will need a housed SLR with at least one strobe. The specific image you have in mind will determine the best lens or lenses to use. For simplicity, you can assume that both macro and wide angle lenses are used in double exposures, either using a unique lens for each exposure, or just sticking with a single lens. Accessories like a snoot or diopter can also be very helpful, as black backgrounds with minimal backscatter are ideal for creating double exposures.
As mentioned, the two most popular techniques for double exposure are either two macro subjects, or the more orthodox macro foreground set in in front of a wide angle background. In both cases you will need to capture black backgrounds around the subject so the second exposure can be placed over the negative black space. High shutter speeds and small apertures are imperative in eliminating any natural light and providing the necessary black background. Planning is crucial in composing two images to work as one. I prefer activating the gird in the viewfinder so I know what lines not to cross.
Macro on macro:
This technique requires the use of your camera's multiple exposure mode setting, which can be found in the menus, and both shots can be taken on the same dive. Because the camera will be combining two images together there will be some light lost in the final image. I find it useful to first test-shoot a single image until I am happy with the exposure and then slightly over expose (maybe 2/3 of a f-stop) when ready to attempt the double exposure .
Maintaining exact focus is extremely important to keep both the exposures sharp, make sure your auto focus is set up to manually change the point of the focus. Additionally, make sure you are not shooting on continuous mode as you don't want an extra frame sneaking in.
60mm 1/200, f 22, ISO, 2x Ikelite Ds-125 strobes, rotating the housing 180 degrees on the second capture
Taking double exposures can be time consuming and a missed second shot can be very frustrating. Therefore, make sure you plan out your composition ahead of time.
For example, taking two consecutive shots of a goby on a whip coral side by side composed exactly the same will not produce a very interesting shot. Either move 180 degrees around the subject after the first capture and shoot the second frame, or if you are confident enough after moving 180 degrees, move the focus point to the opposite side and remember to also rotate the housing 180 degrees. This ensures that the two subjects' heads will be facing each other and that corals will look more natural. The advantage of using this setting is that the raw files will automatically be combined together to form a new raw file, so you can review your image right away and adjust your settings or composition as required.
60mm, 1/200, f22, ISO 100, Ikelite Ds 125 Strobes, moving 180 degrees around the subject
Wide and macro:
Wide angle: 10.5 mm, 1/200, f22, ISO 100, Ikelite Ds 125 Strobes. Macro: 105mm + x10 Subsee adapter 1/200, f25 ISO 100, Ikelite DS 125 strobe with macro snoot
This technique requires using two lenses on two separate dives: one wide angle shot and one macro shot and overlaying the photos during the editing process. There are endless combinations, so be creative!.
Instead of using the camera's multiple exposure setting, you can use the its image overlay setting, which lets you select the files to place over each other. As in the macro-macro examples, you will need two images with black backgrounds. It doesn't matter which image to start with, just remember that later you will be combining the image with one from another dive. Try shooting “dark” sunballs to create a black negative space for the macro exposure, while keeping some interest in the wide-angle background.
A great way to always being ready for double exposure opportunities is to keep around 20 raw wide-angle files ready for double exposure on your memory card , so when you have a magical macro moment you can combine them together.
Wide angle: 10.5mm 1/200,f 22, ISO 100, Ikelite Ds-125 Strobes. Macro: 60mm, 1/200, f25, ISO 200, Ikelite Ds-125 strobe.
Starting by shooting macro subjects is often easier. Critters that don’t move much, and are not surrounded by the cluttered reef are ideal. Stationary subjects allow you manipulate the composition the way you envisioned and isolating the subject against the water column allows for the black background necessary in shooting double exposures.
When selecting subjects, look for ones that will contrast well with the black in the wide-angle exposure, but are also positioned so that you can avoid including any unsightly parts of the environment in the final exposure. Hint: anything living on a whip coral is a super starter candidate!
The single image, as well as the double exposure of the same goby. 60mm, 1/160, f22, ISO 100 , Ikelite Ds-125 Strobes and rotating the camera 180 deg. on the second capture.
105mm + x10 Subsee adapter 1/200, f 22, ISO 250, Ikelite Ds-125 Strobes
Once you become confident in the basics of double exposure, it may be time to try shooting moving subjects. This can be difficult and needs a lot of practice and patience. The best way to start is with a full frontal shot of the same subject. Move your focus point to the left half of the viewfinder, compose and shoot the subject, then move the focus point to the right side and shoot again, being careful not to overlap the subject. Again this can be accomplished entirely using the double exposure setting in your camera.
105mm, 1/200, f25, ISO 100, Ikelite Ds-125 Strobes using inward lighting
This technique requires confidence in your skills, as well as experience: your subject won't wait for you! Think about your exposure while also moving around the subject to plan your composition quickly. Moving your focus points and strobe positioning are also important keys to remember.
Double exposure at night
This is perhaps the most difficult of all. It's extremely helpful to have a dive buddy as a spotter, while also helping to light up your subject. Adjusting your camera should be second nature in total darkness.The last thing you want is to be struggling to adjust your settings only to discover your subject long gone by the time you look up.
60mm 1/125, f16, ISO 200, Ikelite Ds-125 Strobes
Discussing your plans with a buddy before the dive starts is a great way to prepare for any subject you may encounter. I made sure my dive buddy knew before the dive exactly what and how I wanted to shoot my subjects, so when a subject moves quickly, we were both ready. Planning and teamwork can really pay off!
60mm, 1/160,f 14, ISO 100, Ikelite-Ds 125 Strobes
Don't be afraid to use the same technique at night by moving 180 degrees around the moving subject, as well as rotating the camera 180 degrees to create a more exiting image. The potential options are endless, and it's really up to your imagination as what you can create.
60mm 1/200, f5, ISO 100, Ikelite Ds-125 Strobes, moving 180 deg around the subject and rotating the camera 180 deg