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cartTutorials » Camcorders a Safe Harbor blogConsistent White Balance for Live Events
When videotaping live events such as wedding ceremonies, school plays, concerts or dance recitals, the videographer typically has no control whatsoever over the lighting. To make matters worse, the lighting may be constantly changing during the event. A church may have stained glass windows, meaning any entering sunlight may be tinted by the color of the glass. In this case, manually white-balancing the camera may produce good colors, but what happens when the outside light coming in alternates between sunny and cloudy? It can have adverse effects on the white balance. Also, cameras set up at different angles in the church may produce inconsistent colors due to the mixing of electric lighting and window lighting, resulting is mismatched clips when mixing footage from two or more cameras. Stage plays and dance recitals will usually have mood lighting applied, with different scenes having unique lighting treatments to set certain moods. There is no simple way to compensate for all the different setups. Most camcorders allow one custom WB preset, and some now offer two manual presets (A and B), but even two presets will likely not cover the range of lighting you will encounter. You also may not even have an opportunity to test the lighting to set your white balance prior to the event. Many videographers will forego manual white balance and simply set all cameras to the same preset, such as incandescent. While the colors in the recorded video may be off, the idea is that all the cameras will have a matching image and the colors can be corrected in the nonlinear editing suite. Once an appropriate color fix is created in the software, it can be applied to video from all cameras for matching results. I recently did a two-camera shoot of a school play. Some scenes were well-lit, while others were very dark to simulate evening scenes, and many scenes made heavy use of pink gels, giving the scenes an overly pink tint. I simply set both cameras to the "incandescent" WB factory preset, and only changed the exposure during the shoot, leaving the WB constant.
In post, using Adobe Premiere Pro CS3 with the Matrox RT.X2 hardware, I was able to quickly color correct each scene from the close-up camera. I then used "Copy" and "Paste Attributes" to apply the identical effects to the wide camera clips, creating a perfect match when cutting between cameras. There is no possible way I could have attempted changing white balance between scenes during the live shoot. There are certainly many situations where a custom white-balance setting may give the best results if you know the lighting will remain constant for the duration of the shoot. For ever-changing situations as described in this article, your best bet may be to choose a common preset for all cameras and color correct in post. Each situation is unique, and as a video professional you will need to make the call on each shoot yourself. For the play I’m editing, I’m very happy with the speed and ease with which I’ve reached good, matched colors throughout the production. Leaving the white balance alone during the shoot allowed me to focus on composition and exposure, which was enough work running two cameras by myself! The end results speak for themselves.
Interlaced vs. Progressive Video
For decades, NTSC has been the standard for US television and video, using the 29.97 frame per second interlaced video format. All standard definition TVs, video cameras and VCRs conformed to that spec, but now with HD video we hear a lot about progressive formats such as 720p and 1080p. What does this mean? Let’s use a round number of 30 to describe the number of individual "frames" that make up each second of 29.97 interlaced video. Each frame is made up of two "fields", with one field consisting of all the odd lines in the image, the other field having the even lines. Combining these two fields creates a single frame of video. Since there are 30 frames every second, each frame is 1/30 of a second long. As two fields are needed to create a frame, fields must be recorded every 1/60 of a second! The two fields combined create an entire video frame every 1/30 of a second. A typical video camera shutter speed is 1/60 of a second, so the two fields are captured 1/60 of a second apart from each other. When capturing moving subjects, some motion takes place between the capturing of the first field and the second field that make up the frame, so the images in the two fields may not match up perfectly, so fast motion may have "interlace artifacting" apparent in the picture. Hollywood movies captured on film use 24 frames per second, no fields, each frame being grabbed in its entirety in 1/24 of a second. At 24fps, the human eye can perceive that it is not viewing reality, like seeing "flip book images" displayed rapidly one after another, so subconsciously, a little imagination is used in your head to "make it real", filling in the blanks so to speak. This is what gives film its surreal quality, making it different than "video". We don’t know why, but we just like the look of film! In the video world, progressive video is the equivalent of film, capturing complete frames at once rather than mixing two interlaced fields. Many new HD cameras offer the option to shoot at 24p or 30p, which is 24 or 30 frames per second respectively, with the resulting images more closely resembling film than video. Of course, with less frames per second to work with, slow-motion may not come out as smooth, so there are certain trade-offs to get the coveted film-look. The videographer must also be careful to not pan too fast or the motion can look very jerky. It requires an entirely different way of shooting and editing and may not be for everyone. Of course, if you are videotaping a low-budget movie with the intent of having the end result transferred to film, then acquiring the video at 24 frames can make sense since no frame rate conversion will be necessary when transferring from video to film. Fast-action sports like football may also have a better "look" when shot in progressive. Another option for shooting Progressive HD is to use one of the new "60p" formats coming out, which offer 60fps shooting of non-interlaced video, in which case you can get smooth slow-motion. Some tapeless cameras even offer "overcranking", which records double the frames per second so that when played back at the normal rate you can achieve super slow motion! White Balancing Your Camcorder
Different light sources have different "color temperatures", and any object lit with these sources will take on the cast of that source. The human vision system compensates for different light sources, so white always looks white, but camcorders sometimes need our help in determining the best white balance setting for a given situation. In other words, we have to tell the camera what white looks like, and it can then use that as a point of reference to accurately reproduce any color in the scene.
All camcorders will have "auto white balance", or AWB, which often works just fine, but in many cases you’ll want to manually white balance to get the truest color reproduction in your recordings. Most cameras will offer WB presets such as sunlight, indoors (tungsten), fluorescent, and cloudy. Using these presets can work well in many common situations, such as "sunny outdoors". Some lighting situations can be difficult due to mixed lighting, such as indoor lighting mixed with sunlight coming in the windows, typical for church weddings. The color LCD or viewfinder on your camera may show the bride’s dress as having a blue or orange tint for instance. While one of the presets may improve the image, manual white balance will usually provide optimum results to ensure you record the best colors in your video. Consult your camcorder manual for the exact steps to manually white balance your camera, as controls vary between models. Note that cameras usually have to be paused to manually set white balance – you can’t set it while actually recording (though you can switch between the various settings while recording). After switching to manual WB mode, point the camera at something white in the scene, such as a wedding dress, table cloth, aisle runner, white shirt, etc., making sure the white object fills the entire screen (or as much of it as possible). You can use a sheet of paper if you need to, as anything white will work. Push the appropriate camera button to set the WB and then verify that the colors look good to your eye. White objects should look white without colored casts to them. Some higher-end cameras will offer "A-B" settings which allow you to save two custom white balance settings at once. This is helpful when running back and forth between the church sanctuary and bride’s dressing room before a marriage service so you don’t have to keep re-balancing. You will also be able to switch between AWB, WB presets, and your manual WB setting as needed. If you run outside, you can just switch to the sunlight setting most likely, but don’t forget to change it when you go back indoors!
White balance is critical to shooting good video, and should always be checked when changing shooting locations, even when moving from one room to another. While you can always "fix it in post", there is no substitute for good shooting habits. The color corrector in your edit software can certainly improve a video with badly shot color, but it may not ever look as good as if you’d have used the proper white balance to start with. | About This BlogGet the most out of your video and post production tools with tricks and help tips from Jeff Pulera, Safe Harbor's resident video expert and the rest of our helpful staff.Newest Posts |
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