Considering the rising number of underwater videographers out there, it’s surprising that there isn’t more/better information online about white balancing in the water. For amateurs and professionals alike, proper white-balancing is one of the most difficult parts of getting good underwater images. And as critical as it is, the little information that is online is often incomplete at best. There are different approaches to white balancing underwater and people have great results with a variety of approaches but understanding the principles involved is key. When I started shooting underwater I scoured the web for information and ended up having to just learn by trial and error. Hopefully this post can save a few of you that long process and keep some great shots from being ruined.
The first thing is to understand white balance above the water. If you don’t have a solid understanding of that, go figure that out first. The amount and quality of light underwater changes as you go deeper underwater. The spectrum of visible light is filtered out in a specific order – warmer colors first, blues and greens last. This is why underwater images often look colorless and drab. This is pretty basic but how you deal with this depends on what you’re trying to film and in what conditions. Before I dive into white-balancing it should be noted that many videographers use color correction filters to try to compensate for the lack of color at depth. These come in a variety of styles and in both blue and green water versions. The idea is to replace some of the warm end of the spectrum that has been filtered out. Now, to be clear, a lot of people use these, including professionals, but there are a few problems with using filters. The first is that you can’t change the degree to which the filter works. Mostof these filters aren’t accessible underwater which means that in some situations, e.g. shallow or very clear water, you might very well have to compensate the other direction to make up for an overly red image. Another issue is that manual white-balancing through a warm filter can negate some of the filter’s effects, lower your image quality and generally complicates the white balance operation of your camera. Cameras need a reasonably well exposed and complete light to obtain a proper white balance. The more you mess with the spectrum of light coming into the camera, the greater the chances that the white-balance will suffer. Filters also commonly reduce light by a stop and half, something that can be very costly in low light situations underwater. This is especially true when you consider that you’ll usually be wanting the smallest aperture possible to maximize your depth of field and minimize focus headaches. The other problem with filters is that they don’t play very well with video lights which are usually balanced for daylight. This last point brings us to the source of most of the confusion and misinformation regarding white-balancing underwater and an issue which I have never seen discussed on the internet. It is the simple fact that the quality of light changes underwater but the quality of your video lights stays the same. Therefor, in everything but very clear, shallow water, you have to choose, through your white balance choice, to prioritize either subjects which will be within the reach of your lights or subjects which are not within reach of your lights. This is critical. In my opinion, the best images come from a camera white balance that matches your video lights and a subject that is close enough to be fully illuminated by your light(s). This allows a perfect white-balance on the subject and the truest color renditions and a background that is also true to what the eye sees – a deep and penetrating blue. The less water between your camera lens and the subject, the better the video image will be and if you can get close enough to whatever you’re filming to illuminate it with full-spectrum light from your video lights, then you should. However, for subjects that are not close enough, you will be left having to re-white-balance quickly to avoid a faded blue-green image. Conversely if you manually white-balance to compensate for the missing warm end of the spectrum, and then have a subject close enough to fall into the full-spectrum light on your camera, it will have an exaggerated red cast causing you to either turn off your light or again, re-white-balance very quickly. Using a camera/housing combination that allows you to store and easily access multiple pre-set whitebalances is clearly the best option for dealing with this but many housings, including all the housings for the new crop of video DSLRs (it’s a limitation of the camera), don’t allow for this.
You won’t encounter many people who advocate keeping a normal daylight whitebalance and try to get within video light range of your subject. Most people decide that the quality of light as you go deeper is too monotone to be useable and insist on white-balancing frequently to ensure that you are always compensating for the compromised light in the best way possible. I’ve spoken with Howard Hall about his approach to white-balancing and he told me that he white-balances frequently as he descends despite the fact that light within full range of the light maintains the same quality. Far be it from me to contradict Howard Hall – his work speaks for itself – but there are some important things to be aware of with this approach. The first is that, with certain camera systems, you could run into the aformentioned problem of having any subject within reach of your lights looking overly red because of your manual whitebalance compensation. The second is that, depending on your camera, you may simply not be able to get a good manual white-balance in some situations. The camera’s software white-balancing mechanism simply cannot achieve an acceptable white balance in some situations. No camera is unlimited in its ability to compensate for missing light and there is, unfortunately, a compromise to trying to make up for the loss of too much of the spectrum. If you’ve ever tried to white-balance in very dirty or deep water and gotten an image that was grainy and anemic looking you’ve unknowingly discovered one of the least discussed aspects of the art of underwater white-balance: Image resolution and color space are not independent! Read that part again because the implications of this fact reverberate through all of your whitebalance decisions. I won’t pretend to understand the details of the optical physics, sensors and compression schemes behind this fact but the implication is that if you try to manually compensate for the loss of too much color, you will degrade the quality of your image. This is why it is usually best to try to achieve good colors with as little manipulation of the image as possible. An image that has been pushed too far, even though it may not be visibly bad at the time you record it, will have less latitude for color-correction in post. Sometimes, in keeping with the idea of shooting flat to optimize post-production options, the tools available to you to fix the image in post are more robust than the tools you have to fix the image in camera. Recording a clean image without proper whitebalance can often yield a better final image than recording an image that has been degraded too far trying to compensate for light wavelengths that simply aren’t there. That doesn’t mean don’t white-balance, it just means you should be aware of your system’s abilities. As camera technology advances, many of these issues are diminished. The sensors in the new Canon DSLRs are more sensitive and thus better able to achieve a decent white balance in low-light or bad-light situations than, say an HVX200. The best option is to test your camera system as thoroughly as possible before an important shoot to see what techniques yield the best results. Bring your test shots into your editing software and play with color-correction options. And get the best underwater lights you can. A lot of time and money and effort goes into getting yourself in the water with a camera – it’s not worth risking that your images will be ruined by poor white-balance.