What are the best focal lengths to use underwater?
Deciding which focal length to use while shooting underwater primarily depends on what type of photos you will be taking. For this article let’s examine a couple different focal lengths for shooting underwater photos and how they will come out.
Wide Angle Close Ups
When you shoot portraits underwater in the open ocean you might find that you get the most success with a wide angle lens shooting in the range of 14 – 18 mm range. At this range you are forced to get really close to your subjects. In the open ocean this is good because it minimizes the amount of particles that will be highlighted in the water when you capture your shot. See our article on Backscatter.
This is somewhat the catch-22 on underwater photography. A lot of people use very short focal lengths (generally under 20 mm). This short focal length requires them to get very close to their subjects in order to properly fill the frame. This approach is needed because at a farther distance (say greater than several feet) your flash loses effectiveness. In addition you pick up all the dirt and debris in the water. Remember the golden rule of underwater photography: Get In Close and Fill it with Light.
Let’s examine this shot above. This shot was taken with a 14 mm lens. The subjects are literally 2-3 feet away from the camera. Yet even at this close focal range you can still see a lot of particles and debris in the water (which was very clear water).
If you have more control over your environment and the water you are in (such as in a clear water pool) then you will be able to capture some medium range portraits. Think of these shots as one that shows someone moving through the water, interacting with an object, etc. Generally they show the full body of the subject as well as possibly some props. These may be shot in the 28 – 50 mm range.
To be successful with these shots at a farther distance from your subject you need two things. First is clear water, second is plenty of natural light. This approach is harder when shooting during scuba diving in dark areas. There simply won’t be enough light to properly capture a subject 20 feet away. However in shallow water, with lots of sunlight coming in and clear water you can capture a pleasing perspective on a reef wall or someone diving into a swimming pool.
Lets look at this photo. This one was taken at approx 24 mm. These are the same two subjects as in the photo at the top of the article. In addition, the second photo was taken in a swimming pool and not the open ocean. Notice how much detail is lost in the subject of the girl in the back compared to the boy up front. The girl is probably only ~12 feet away while the boy is probably ~8 feet away. Each foot that is added in distance between you are your subject adds all kinds of junk in the water to be captured and destroy your light. While this shot tells a fun story (of these kids trying SNUBA for the first time), it is much more difficult to capture good light and color at longer distances.
Truth be told, there are not a lot of circumstances where a telephoto range will be used in underwater photography. The exception to this of course is when you are using a telephoto in a very short distance from your subject. This is because when a telephoto range is used to enlarge a subject far away, let’s say 100 mm or higher, a great deal of the detail is lost as the light travels through the water.
So when you take advantage of telephoto zoom lenses underwater, remember to keep your subject distance in mind. Just because you can zoom into a shot far away does not mean that it will come out clear. If used for short physical distances then you will have greater effectiveness.