The Art of White Balancing
by Nigel Cooper
I thought I would write this article to clarify a few mysteries and myths about manual white balancing when shooting with digital formats such as Digibeta, DVCAM, HDV, Mini DV etc.
Many camera operators are all too keen to reach for a white balance card and carry out a manual white balance test with their camcorder without stopping to think of the possible implications; sure, this will ensure perfect whites, but have you ever stopped to think about the damage you could be doing to the remaining colours in the image; not to mention the destructive effects this can have on human skin tones.
A little history
Many years ago, older analogue CRT tube based broadcast cameras had to be white and black balanced each time they were used. This was due to many varying factors. They were constantly being serviced by on-site engineers to keep the three tubes physically aligned. They were also very sensitive to temperature too, so in the case of external ENG cameras they were constantly being aligned by carrying out black and white balancing operations.
These days things are a little different and we donít have to concern ourselves with these analogue issues anymore. This is mainly due to the modern CCD (Charge Coupled Device) image sensor chips used in todayís modern digital camcorders. Combined with other modern electronic advances we now have very stable camcorders. Alignment drift and temperature sensitivity (within reason) are now well and truly a thing of the past.
Modern camcorders have built in pre-set white balance settings as well as a manual white balance adjustment feature. What many camera operators fail to realize is that modern camera manufacturers such as Sony, Panasonic and JVC go through an awful lot of time, trouble and expense to get these pre-set 5600K (daylight) and 3200K (tungsten) settings perfect in a controlled environment; they are scientifically tailored to give you perfect colour reproduction and skin tones.
Whenever possible you should aim to use the pre-set 5600K or 3200K settings on your camcorder; hereís why: letís say for example that you have lit a studio with 3200K tungsten lights and you have your interviewer and interviewee seated on set and standing by. As long as your lights are outputting exactly 3200K (or pretty close to e.g. 2900K) you should choose the preset 3200K setting on your camcorder to ensure the best possible reproduction of skin tones on your talent. If on the other hand your lights are not outputting 3200K and they are outputting say 2200K or 4100K, you will have to use a white card and carry out a manual white balance procedure in-camera. This manual white balance procedure will adjust the cameraís CCD image sensors and the RGB characteristics to the white on the white card, but it will also adjust all the other colours according to its new white point of reference, including your talentís skin tones; this can be a bad thing.
The technical bit
Modern camcorder manufactures like Sony, Panasonic and JVC spend obscene amounts of money to scientifically get these pre-set 5600K and 3200K settings perfect in a controlled environment. By using these presets, coupled with high quality light sources such as Tungsten halogen, film quality HMI or MSR daylight sources or Kino Flo fluorescents, you will retain more accurate colour reproductions and better skin tones.
The manual white balance setting on your camcorder is (in its most basic form) an in-camera effect and once you start messing with these settings by carrying out a manual white balance by using a white card, you are forcing the camcorder to adjust its RGB (Red, Green and Blue) CCD image sensors and their preset characteristics (assuming you are using a 3 CCD chip camcorder, though a similar thing happens in single chip cameras). This in-camera adjustment is a trade off; you will achieve true whites, but you could also sacrifice true colour reproduction and natural skin tones. The camera is now telling its image sensors to balance all the other colours according to your new white point of reference i.e. your white card. This practice shifts the colours picked up by the CCD image sensors and shifts them away from where they were naturally set by the manufacturer in a controlled environment.
To white balance or not to white balance
Personally, I try to avoid manually white balancing to a card because I like my shots to have natural skin tones and accurate colour. I achieve this by making every effort to control my lighting environment by using high quality light sources. Of course I don't always have this luxury, for example, in supermarkets under fluorescent lighting. Of course in this instance and many like it, you will have to white balance manually. In reality whites are rarely true white and they often appear as various different shades of colour as they become tinted by either light from variable sources of light, or from light reflecting off coloured objects nearby. This could be very subtle, think 'apple white' 'egg shell white' or in the case of a white cottage in the middle of a rape seed field, a subtle shade of 'daffodil white'.
Take this example: if you were shooting in the late afternoon when the sun is low in the sky and there is a beautiful golden orange coloured light splashed across the entire scene by the setting sun, you will notice that white objects in the scene will not be pure white, instead they will be slightly yellow, golden or orange, or a combination of all three as the white objects in the scene reflect the natural late afternoon golden light projected by the sun.
Now, if you place a white card in that scene and carry out a manual white balance, your whites will be pure white with no beautiful late afternoon colour in them at all, but the rest of the scene will change in colour also, for the worse, and in this instance the whole scene will suddenly become blue and very cold looking, more like a late winter afternoon as apposed to a lovely summer evening. Would you want that to happen? me neither; that would be like erasing Godís art from his canvas. This happens because the camcorder corrects all the colours relative to what you have instructed it to interpret as white via your white card, it can't think for itself, you on the other hand can.
In most outdoor shooting situations where the scene is predominantly illuminated by daylight, I would suggest that you aim to use the 5600K preset on your camera so it will display colours more naturally. Remember, you can always white balance a shot in post production later on if you are not 100% happy with it, though this is a different ballgame and unless you are a master of grading in post you would be much better off white balancing manually at the shooting stage. Personally, I like to get things right at the shooting stage.
The same rule should be applied indoors when shooting under 3200K tungsten lighting (or 5600K daylight lighting units for that matter). Use the preset 3200K setting and make sure your lights are outputting close to 3200K, correct them with colour correction gels if necessary.
Hollywood production companies usually always use presets when shooting on HD. If they are shooting in a studio environment and the lights arenít outputting exactly the colour temperature they require, they will not carry out a manual white balance to compensate, instead, they will use colour correction gels on the lights to get them to match the camera, hence, maintaining accurate colour reproduction and natural skin tones. However, they always use a colour meter to get their equations 100% spot on.
If you are shooting in a studio environment or any other indoor situation where you are using Frenels, HMI's, Dedo's, Kinoís or whatever, you should try not to mix your light sources other than for artistic reasons i.e. donít be tempted to use 3200K tungsten lighting units (i.e. Redheads) with 5600K lighting units (i.e. Kino Flo Fluorescents lamped to daylight) in the same shot. Mixing light in this way can spell disaster. You will be forced to white balance and even then you could get some questionable and unnatural results.
This is why professional Lighting Cameramen stick large sheets of colour correction gels to the inside of say office windows when they are shooting an interview with the MD inside with tungsten lighting. Having said that, things can quite often be totally out of your control i.e. take a TV commercial that was shot in a large supermarket. As you know most supermarkets have banks of architectural fluorescent lights up in the ceiling, Iím talking about the office ďgreen spikeĒ variety here. In this instance it would almost certainly be far too costly for the commissioning company to change every bulb in the supermarket to 5500K colour corrected bulbs. Instead if they were using Kino's they would ask the caretaker to grab some of the spare bulbs from the stock room and they would then take out the colour correct Kino Flo bulbs and use the architectural bulbs in the fixtures for the shoot.
For other lighting units they would use a plus-green gel and the aid of a colour meter to get the source keylights to match the hundreds of architectural fluorescents in the supermarket; finally a manual white balance would be carried out.
In any instance, when you must carry out a manual white balance test you should always use a proper white balance card that is perfect prime white and not use somebodyís T-Shirt that might have faded or worse, picked up a hint of pink of the wifeís blouse. The same can be said about using a sheet of white A4 paper from the office location where you are shooting; the paper might have been lying in the sun for a couple of weeks and might be ever so slightly yellow. These factors will affect your manual white balance calibration and subsequently the final colour reproduction and of course, skin tones.
Of course artistic lighting is a different thing altogether; for example you could have a 5600K keylight, then experiment artistically with say a 3200K Dedolight for the fill or backlights. There is a difference between doing something on purpose in an artistic way and achieving a rather dodgy result accidentally; your lighting must be by design and judgment.
Another example of necessary manual white balancing is when you are shooting under sodium street lighting, which are pretty much a big spike of orange light and not a lot else (neither 5600K daylight nor 3200K tungsten). Also, white balancing can sometimes be necessary if you need to ensure that the whites appear identical when shot in different light sources. However, the general rule is; only white balance when you absolutely have to. In a controlled lighting environment it is always better to balance the lights and use the camcorders presets to maintain better skin tones and accurate colour reproduction.
©2005 Nigel Cooper