Probably the #1 trick for filming dance movies that can be effectively viewed for instructional purposes is: The dancers must not wear black pants or stockings! When the dancers wear black, it will be difficult, if not impossible, for the viewer of the movie to tell the right legs from the left legs. Instead, have the men wear khaki pants, and the ladies should wear light tan stockings and pastel skirts.
Since this suggestion is so very "counter" to dance fashion, a word of explanation is in order: the digital cameras and camcorders have very limited "dynamic range" when compared to what we can see with our eyes. That means that the range of the darkest shadows to the lightest highlights is compressed by the cameras, effectively "erasing" all the visual details that allow our eyes to easily discern left from right among an entwined collage of black-clad legs.
Here is an example of the problem. Looking at the leader, can you tell his left leg from his right?
Back-lighting (bright lights behind the dancers) will result in under-exposing the dancers, giving a dark and muddy appearance exactly where you want the most detail to be visible. When filming a dance pattern under "studio conditions," back-lighting is easy to avoid. However, when filming under typical "dance work-shop conditions," you may have to experiment with several camera angles to avoid including bright lights in the background of your movie.
This caution to avoid bright lights behind the dancers also applies to avoiding bright lights above the dancers. This happens all too frequently as a result of using a very wide-angle lens setting to capture the dancers from top-to-bottom on a relatively cramped dance floor. The wide angle of the lens also picks up a view of the ceiling and lights above the dancers.
If you can't avoid back-lighting, try to minimize its effect with one or more of the following techniques:
Here are two examples of back-lighting. On the left, exposure lock prevented the bright light in the background from darkening the rest of the frame. On the right (an early "learning experience"), the back-lighting was terrible, and the movie had to be post-processed on the computer (with great loss of detail) to be even marginally usable.
When filming dance patterns, "more" is not necessarily "better." The Tango Movie Tool was designed for 320x640 resolution, at original frame rates ranging from 10 to 30 frames/second. At this size and speed, most PC's have enough power to play the movies at their original frame rate. My aging laptop, an old Pentium 166 MHz, represents the lower limit of practicality: it can barely play a movie at 15 frames/second. However, even movies shot at 30 frames/second will play smoothly enough at 1/2 speed to convey the fluidity of any dance pattern.
I made a version of TMT that works at 640x480 resolution. Since each frame contains 4 times as many pixels, the computer needed to have a much faster CPU and video card to keep up with 30 frames/second. The additional resolution, however, didn't seem to "show" anything extra that was useful from a learning standpoint.
I have found a wide variation in the usefulness of different models of digital cameras, all of which are advertised with the "movie feature." The absolute best (at an affordable price) is the Fuji F-700, which can take 320x240 movies at 30 frames/second continuously until its memory card is filled. For the largest XD memory card of 512MB, this translates to 15 uninterrupted minutes of filming.
Almost all other cameras are limited to movie "clips" of 30-90 seconds duration. This is not a painful limitation when filming work-shop material, since the instructors typically are showing one thing at a time. However, it is a limitation when trying to film 2-3 minute long "show" or "demonstration" dance presentation.
Other cameras I have tested include:
Another factor to consider is the combination of lens "speed" and ISO setting, and in this case, faster is definitely better, due to the generally marginal lighting in most dance venues. Here are sample values for the three cameras mentioned above:
For low-light filming, of course, nothing beats a "1-lux" camcorder. The only drawback to using a camcorder is the potential difficulty in transferring the video into your computer in an AVI format. For this latter purpose, mini-DV digital camcorders are superior to VHS-C or Super-8 analog cameras. Easy transfer of mini-DV digital movies to the computer is supported by a wide range of inexpensive cards and software.