Dema 2008 – White Balance Technical Seminar


This year at DEMA I was asked to do a seminar on mastering underwater white balance, a topic near and dear to me. I have spent countless hours over the years experimenting, researching and testing various methods. The result is a body of knowledge and a toolbox of techniques that enable me to achieve that desired look in almost any underwater conditions. Read the transcript below:

Mastering White Balance for Professional Video Results

White balance is the essential technique for professional color.  Learn the tips, tricks and pitfalls of expert color control

INTRODUCTION

I can’t recall how many times I have been told about the “one” manual white balance [WB] method that really works. When I then apply that method, I discover that like many of it’s predecessors, it has limited application and varying results. When you think about it, given that one is shooting underwater, is there such a thing as “perfect” WB? On many occasions, I have reviewed a piece of footage with several capable shooters at same time, and frequently there is little agreement as to whether the WB was good or not. Some folks like it more colorful while others like it more true to what you see underwater. Depending on the subject and environment, both perspectives have merit.

On land, manual WB is wonderful for capturing footage with as accurate colors possible. Technically, WB is “a function which gives the camera a reference to “true white” — it tells the camera what the color white looks like, so the camera will record it correctly. Since white light is the sum of all other colors, the camera will then display all colors correctly”. In addition, by “tricking” the camera’s manual white balance, the shooter can either “cool” or “warm” the scene to achieve the desired effect. For land shooting, this process is pretty straight forward once you spend some time working with it.

Underwater, because various colors fall off at differing rates, the concept of WB gets much more complex. We move from a world saturated with white light (complete color spectrum) to one growing ever more blue as one descends. More specifically [excerpt from www.vividlight.com] “. The first color to fade and disappear is red. At a depth of eight feet, red light starts to fade and it is filtered out of the visible light spectrum by 15 feet. The next diminishing color is orange at 15 feet; by 50 feet, it has disappeared. Next to fade are yellow, green blue, indigo and violet.”  Because of this fact, auto WB becomes less and less useful the deeper one goes because the camera does not have enough color spectrum information to properly adjust WB. Even on land, auto WB tends to do an OK job but certainly not professional. Moreover, even just several feet below the water, a good manual WB can markedly improve the image quality.

The fall off of colors in the light spectrum as one descends creates big issues for getting that “perfect” WB. Unfortunately, the problem is far more complex than this. Many other factors come into play which impact the WB.  I have spent a good deal of time experimenting in this area, and have come up with several categories of variables that impact WB. Effectively managing these variables while shooting underwater will dramatically impact the results of one’s manual WB. I am aware that there are dozens of ways to slice and dice this, however this framework works for me.

ENVIRONMENT:

•Depth – How deep are you shooting? The Deeper you go, more colors fall off the visible spectrum.

•Ambient Light – How much available natural light (read sunlight) is there?.

•Angle of light – Is the sun overhead or on the horizon?

•Visibility – What is the concentration, color and size of particulates in the water?

•Distance – How far are you from your subject?

•Angle of shot – Are you shooting up, down or level?

•Shot relative to the natural light source (sun) – Are you shooting into the sunlight, across it, with it at your back?

•Color of environment – What is the pervading color of the corals, rocks or sand where you are shooting?

•Color of water – What is the underlying color of the water? (Combination of the above, plus algae, plankton, etc)

EQUIPMENT:

•Manual WB Control – Does your housing provide access to WB controls?

•LUX rating – How deep can you engage manual WB on your camcorder?

•Color Correction (CC) Filter – Does your housing accept CC filters? Can you remove underwater? What kind is it (green water, blue water)? Is it acrylic or glass?

•Lights – Do you have ext lights? What type are they (halogen, HID, LED, etc)?

•WB Slate – Do you have a “white” slate? What type do you have (warm, cool)?

•Camcorder Settings – Do you adjust cam settings such as Color Offset, WB Offset?

•Other – Do you use an expo disc or other WB device?

TECHNIQUE:

•WB Surface – Do you use slate, sun on water surface, sand, sponge, hand, fin, etc?

•WB Depth – At what depth do you WB in relation to depth you are shooting at?

•WB Angle – How do you adjust the angle of natural light relative to you WB surface?

•WB Distance – How far are you from you WB surface?

•CC Filter – At what depth and under what conditions do you use your CC filter?

•Hybrid – Do you ever WB with both lights on and CC filter engaged?

The above list may seem a bit overwhelming. I have found however that any one of the above variables on any given day, can have a huge impact on the quality of my WB. On the other hand, the more I understand these variables, the better I get at achieving more consistent and better quality WB. That being said, I have a long way to go!

First things first, what am I shooting with?

Equipment:

•Sony EX1

•Gate EX1 Housing

•Light & Motion Sunray 2000 Lights

•Lenses: Flat port, Std Dome

•Manual WB Control – Yes, one touch manual WB

•LUX rating – very good (I can typically WB down to 25 meters, +/- depending on ambient light)

•CC Filter – Yes, UR PRO Blue Water flip filter (glass)

•Lights – Yes (HID)

•WB Slate – Yes, cool bluish slate and plain white slate

•Camcorder settings – No, do not mess with color/wb offset as impact seems marginal compared to manual Wb

•Other – Yes, Expo disc but still to experiment with

Considering the above factors, here are some of my personal findings regarding WB using my equipment in varying conditions.

IDEAL CONDITIONS:

(depth of 10 meters or less, sunny day, late morning/early afternoon, excellent visibility of 30 meters or more, 3 meters or closer to subject, relatively level with subject or slightly below, sun over your shoulder, environment either neutral colored or no dominating color, and clear blue water)

Generally speaking, the better the conditions, the easier it is to achieve decent and consistent WB using some basic techniques. In ideal conditions, engaging the CC filter and balancing of a white slate held at arms length often proves to be sufficient. Warming the image is accomplished by angling the slate away from the sun (less light on it) and holding it further out. Cooling the image is achieved by the converse, angling the slate to collect more light and bringing it closer to the lens. I achieve further refinement in colorful environments by holding the slate close to the dominant color (say bright coral head) and balancing.

Alternatively, in shallow bright water, I often balance off the sun on the waters surface. I simply point my cam at the sun ball on the surface and WB. To cool the shot, I zoom in on the sun. To warm it, I zoom out. If the image is still to warm (red) I ascend a bit, WB, then descend to shoot. This technique proves handy at times when the slate is causing the WB to be too red. To be honest, I use this technique more than any other.

If neither slate nor surface are deliver the WB I need, I then use environmental surfaces. If my picture is still too red, I balance of a pink sponge, my hand or similar. If I need to spice up my colors or shift them, I balance off a sandy bottom. A variation of this technique that I have found to work is to hold my slate very close to the area I am filming, say a coral garden (being careful not to touch the coral of course) and angle it to catch as much light as possible. This tends to reduce the dominance of a particular color from the reef in your shot.

When shooting utilizing ambient light, in most circumstance I keep my CC filter on. I find the CC filter delivers superior contrast, better blues and a more pleasing image. Even in very shallow depths, proper WB technique tends to deliver (IMO) better WB with CC filter filter than without.

DEEPER AND LOW VIS CONDITIONS:

(depth of 20 meters or more, cloudy day, early morning/late afternoon, ok  visibility of 15 meters or less, 3 meters or further to subject, relatively level with subject or slightly below, environment dominated by reddish or greenish color, and aqua/greenish water)

Good examples of the above conditions include locations like Galapagos, Cocos, and Socorro where much of the sea life if found deeper and lighting and vis are relatively poor. Shooting in deeper and low vis conditions presents some real challenges to achieving ‘good’ WB. For one thing, most red light and much of the green light have disappeared from the color spectrum. In addition, the underwater topography is often covered with hard coral, barnacles or algae of a red/pink hue which enables them to absorb as much of this light as possible. To further complicate matters, plankton of a similar hue abounds in the water.

When one tries to WB using standard techniques is such conditions, the results are often unacceptable. In order to approximate “true” white, the camera cranks the red color contribution beyond the normalized range. The result is an image that is very unnatural in appearance. The sea floor turns glowing red, the water turns purple, and pelagic fish turn pinkish. In addition, the colored plankton in the water are accentuated, turning ok vis into poor and cloudy vis.

In my experience, use of the CC filter engaged consistently delivers a ‘better’ image in such conditions than with it removed it. The primary reason is that the CC filter tends to increase image contrast and provide a greater range of colors in the scene. By limiting the amount of blue light reaching my sensor, the relative red contribution is increased and subjects that have red in them appear with more color and of greater contrast. There is often debate on this topic and there are instances in deeper diving where I choose not to use the CC filter. This is determined by how much I am favoring foreground vs. background. However, under in most situations, I tend to favor the use of the CC filter. The CC filter does reduce the amount of light getting to your sensor, this is a fact. For cameras with poor Lux ratings, the issue can prove significant. However, when you are at a depth where Lux rating becomes an issue, frequently you are unable to WB anyways.

For example, the A1 frequently cannot WB below 10 meters (disclaimer: this is based on observations of several shooters I know and is not always the case). As such, this section does not really apply to this user. My EX1 frequently WB’s at 25 meters, so I have these issues to address. Continuing, I find that the CC filter enables to me to WB deeper than when I WB without it. The reason for this is that without a CC filter at depth, the camera is unable to lock on what it considers an acceptable WB value because of the virtual absence of red light contribution that is necessary to make ‘white’.

Experimentation is critical to this next point. Because of the above considerations, even if I “can” WB down at 25 meters or deeper, I typically do not. My reasoning is simple, I do not want bright red sea floor, purple water and pink sharksϑ I am looking to generate an image where the water is blue with subjects that are sharp, ‘appropriately’ colorful and well contrasted. To achieve this, I WB at a shallower depth (during my descent) than the depth I am shooting. The environmental conditions play a key role in exactly what depth I choose to WB at. Generally speaking, I WB more shallow when there is less ambient light, worse vis, more red/magenta in the environment (coral, algae, plankton), and greener the water. I tend to WB less shallow when the above conditions are reversed. For example, if I am shooting at 25-30 meters using ambient light, I will WB between 10 to 20 meters based on my assessment of the environmental conditions. Better conditions and I WB closer to 2/3rd s my shooting depth. Worse conditions and I WB closer to 1/3rd my shooting depth. To fine tune my WB (warm/cool) I use techniques described in the Ideal Conditions section above (slate, surface, zoom, angle, distance).

SUPPLEMENTAL LIGHTING CONDITIONS

MACRO AND NIGHT DIVING

Even the most powerful of supplemental lights have a very limited reach in day time diving. Whether you use HID, LED, halogen or whatever, this reach is limited to feet and meters. My HID lights generally prove ineffective for subjects greater than 3 meters from my lens. Beyond that, subjects are grey and shades of blue. As such, for wide angle and panoramic shooting, proper WB utilizing available ambient light will tend to produce images that are more balanced and with far greater range with color than lights. Simply put, a CC filter in conjunction with a good WB can reach as far as the camera can see. Your lights can only reach a few meters at best. If you goal is narrow foreground with color and little or no color (other than blue) in the background than just lights is a good choice.

I tend to use lights in two primary situations, macro and night diving. In both situations, I do not us CC filter. I simply adjust my lights to hit my slate in front of my lens and WB. If you are shooting macro, be sure to have you slate very close to your lens and/or zoom on the slate. This increases the amount of red light the camera sees and ‘detunes’ the WB adjustment. The result with be that your nice tight macro shot will not have overblown reds and greens. I have found both auto and daylight WB settings do not produce as consistent and quality results. Again, this is another area of opinion and preference.

HYBRID SITUATIONS

In certain conditions, I find that there is very little color information to distinguish my subject from the background environment. A good example of this is shooting marble rays in Cocos. The water was blue-green with decent vis. The topography was of black volcanic rock with barnacles. Unfortunately, the marble rays were perfectly adapted to these conditions, with skin patterns and colors the same as their surroundings (good for rays, bad for shooterϑ). When shooting the marble rays without lights, the resulting image was a black disc floating over black rock in blue water. I knew the rays had beautifully white undersides with gills and mouth and white freckles on their top side. When shooting with lights and no CC filter, the ray looked spectacular, but it’s background was low contrast and the water had a greenish tint. So, how to make the ray pop with lights and still preserve the background contrast, and blue water?

My answer is to employ a hybrid technique utilizing both CC filter and lights. The goal is to increase the reds on the subject by hitting it with your lights, but not turn it into a red orb in a blue sea. To accomplish this, I WB with CC filter on at 1/3rd to ½ my shooting depths. I use one of the techniques listed above to ‘cool’ the image. Descending down to the subject, I try to hit the subject with edges of my lights (the overlapping zone) vs. direct lighting. I move back from the subject to reduce the red contribution of my lights. Every foot back makes a big difference because of rapid fall off of my lights. The resulting image from this technique is a well contrasted subject with colorful highlights silhouetted on a background with good contrast and blue water. In post, I then can drop the red gain/levels to get that white underside just right. The rest of my image does not required color manipulation.

Note, I find this technique is difficult to ‘master’ and more often than not yields a less than ideal result. If the subject is close to surfaces with lots of red/magenta (coral, algae, barnacles) the result will be blown-out disco red backgrounds! This technique is also less effective for colorful subjects and colorful environments. In addition, if there is lots of plankton in the water, you will get some very purple/magenta water. The technique is best utilized in low contrast, low color environments where there is little to distinguish your subject. The lights offer that additional “pop” to your subject without turning your image into a psychedelic dreamscape.

CONCLUSION

The title of this article is ‘Perfect White Balance”. I personally do not believe that such a thing exists in underwater shooting (see intro paragraphs). I believe a more appropriate title is ‘Pleasing White Balance’. WB techniques that result in footage that most of your viewers deem as desirable and pleasing to view, is what one should target. In my experience, blue water (considering appropriate hue variations depending on location and conditions) is essential for quality footage. Furthermore, well contrasted subjects in bright and colorful backgrounds (when appropriate such as reef situations) are highly desirable. The goal is to preserve the ‘natural’ look and feel of the environment while offering an enhanced view which highlights the colors and beauty of the subject you are filming. Pleasing WB should be subtle yet effective. Try to avoid boosting your subject colors to the detriment of look and feel of the environment. A colorful subject in purple water is not natural or pleasing. Again, subtlety is your friend.

My recommendation is to experiment with a variety of techniques and find the ones that work for you. I do not believe in “one” magical technique that works in all conditions. I believe you need a tool box, which includes both technique and equipment, which you rely on to achieve pleasing WB results in all kinds of conditions. In this discussion, I presented the elements of my WB toolbox and my current thinking on when and how to use these tools most effectively. I believe I am only beginning to grasp this concept and have long way to go to ‘perfect’ it. My goal is NOT to state that my way the “right” way. I firmly believe there are a variety of methods to achieve pleasing WB.

– Shawn Heinrichs

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