Understanding Lighting

Introduction
object appear larger underwater Taking pictures underwater can be frustrating. Sometimes you can spend a long time taking that just perfect shot, only to be disappointed later when you download the pictures from your card and they have a deep blueish hue, or a are filled with white spots. Then odds on you have a problem with the lighting in your photos. One of the keys to taking great photos underwater is to understand what is going on with light and particles in the water. Once you have, the results should be a quantum leap in the overall quality of your underwater pictures.

Light and water

light & color loss underwater If you remember your open water course, you will have learned that objects appear 33% closer and 25% larger underwater due to the refraction of light as it passes from the water into the airspace inside your mask. This property of refraction produces many interesting effects as light passes from water to air, the most well-known is the beautiful rainbow. After rain with the air laden with moisture, white light is split into its base color components as it passes through the water particles in the air.

The reason this phenomenon happens is that each component color of white light has a different wave length, with blue being the shortest and red being the longest. As the light passes from one medium to another it is refracted, with the shorter wave lengths refracting more and thus the light being separated out. These different wave lengths cause light to behave very differently in water than in air.

When it comes to water, light has a problem travelling through it uniformly due to the increased density of water (compared to air). The lights with the longer wave lengths struggle to penetrate deeper and deeper into the water and are lost. This is why a red colored object will start to appear more greenish as you start to take it deeper, and as you progress it will become a brownish/blue color. Eventually the only color is a darkish blue, and this can seriously affect underwater photos.

White balance

One of the first methods you can use to compensate for light issues underwater is to adjust the white balance of the camera. This is completely electronic and does not use an external source of light. By re-calibrating the camera sensor to an object known to be white such as a white slate (or sand or bare hand), the camera electronics can then re-adjust the effect of the different wavelengths of light that hit its sensor to compensate for the depth. This is possible because the camera knows that white light is composed of a spectrum of wave lengths and what each wave length corresponds to color-wise. As such, the highest wave length will always be a red color, and the shortest wave length will always be a blue color.

white balance

While this technique is great for novice photographers and in shallower water, it is far from perfect, since so much of the subtlety of colors are lost, especially at depth.

Strobes

macro set up To get great results from your underwater pictures you will eventually have to use strobes, which are simply an underwater flash. These are much more powerful than a normal land flash, since they have to put so much more light in the picture. As a result, unlike their land counterparts it is rare to point the strobe directly at the subject of the photograph, since this will often result in over-exposed pictures with large swathes of white across it. Another unfortunate result may be that the flash will light up every tiny particle in the water and the picture will be covered in white spots called backscatter. It takes time and practice with your own setup to get the best results with your strobe positions, since each system has its own quirks. The one underlying principle though is that you are generally aiming to reduce the amount of light hitting the object to a level that will produce great pictures without them being over-exposed.

Snoots

snoot underwater photographysnoot underwater photography

A recent addition to the underwater photographer’s arsenal is the snoot. It is primarily used in macro photography, and can vary from a small dedicated light fitted to the top of the camera to an attachment that covers a regular strobe leaving a small hole with a nozzle to really control the amount of light produced by the strobe. They are more commonly used in quite artistic macro shots where the entire background is darkened and only the colorful subject in the foreground is lit.

Macro Vs. Wide-angle

The principles of lighting in macro and wide angle are fundamentally the same, the main difference being a technical one. The bigger the subject of the picture, the greater the arm span of the camera strobes that is needed. This is so that you can point the strobes “off target” and still get the desired lighting effect. Some dedicated wide angle systems will have arms that span nearly a meter each way from the camera body.

Finally, the key to mastering underwater lighting is practice, practice and more practice.
macro arlequin shrimpstingray wide angle

At what depth exactly do I have to start accounting for loss of colors?

There is no set rule here and it really depends on the water conditions, while in clear tropical waters red starts to disappear at about 6-7 meters, this can be shallower if the water is turbulent or has limited visibility; as a general rule the more particulates are in the water, the worse the visibility, and the more overcast the day is, the shallower the different wavelengths of light will be absorbed by the water.

Do I need to have strobes as an absolute must to take great photos?

Simply put, no. While if you are taking photos relatively deep in the over 25-meter range then a strobe becomes vital, it is not completely necessary to have it to take great pictures shallower; in fact, several award winning photos in the last few years were taken without any strobes, just a manual white balance. It must be said that if you plan on doing a lot of macro photography then the strobes do tend to come in handy since the camera is very close to the subject, which is often not positioned in plain light. For the bigger subjects, great shots can be taken without any strobes at all.

Do I need to have a double strobe set up or can I just choose to use one strobe?

When it comes to lighting, it’s about symmetry; using 2 strobes is the ideal but you can easily get by with one strobe only. Mainly, 2 strobes are ideal for taking wide angle pictures, where you need the wider angle of lighting the subject. One strobe photography can produce amazing results in macro photography, with the strobe arm positioned above the camera pointing in the subject’s direction or above it.

Is it possible to have two different strobes on either side of the rig?

While this is possible, it is not recommended, since different strobes will have different power rating generally, and even strobes with the same power rating from different manufacturers will have somewhat of a different brightness. This disparity in brightness will lead to photos that are unbalanced, with too much light on one side of the subject and too little on the other. If you decide to opt for only one strobe first, then try and find a pair of strobes you want to use, buy both and start only using one, or decide which pair you want and then buy them one at a time.

USAFrenchGermanSpainRussiaSwedish