There is an almost overwhelming choice of consumer and pro-sumer video cameras available on the market today. The most popular are models from Sony, Panasonic, Canon, and JVC. There are also at least a dozen camcorder recording media formats out there. They include 8mm, Hi-8, VHS-C, S-VHS, miniDV, DVCAM, DVCPro, HDV, microMV, DVD, SD, and MicroDrive. All of these cameras are designed primarily for topside use in mind. Only a subset of them are well suited for use underwater. We’ll show how to whittle down the list of formidable candidates.
The first thing to consider is which cameras even have underwater housings available for them. Details of housing selection are covered in this section as well, but if you’re going to use a camcorder underwater, it needs to be in a reliable housing. Most housings are made by third-party companies, not by the camcorder manufacturer. Housing companies target primarily Sony, Canon, and JVC makes of camcorders in their product lines, with Sony being the most supported brand of camera.
The next thing to consider is recording format. With digital video gaining traction since the late 90s, the analog formats (8mm, Hi-8, VHS-C, S-VHS) are quickly becoming obsolete. Some of the new MPEG-2 based formats such as microMV, DVD, SD, and MicroDrive are OK for some types of use, but they have the major drawback of being ‘lossy.’ This means that you permanently lose video quality due to the MPEG-2 compression performed by the camera as it stores to tape or disk. The DV (digital video) formats store much better quality video to tape than MPEG-2. DV formats include miniDV, DVCAM, DVCPro, and HDV. The last three are professional flavors of DV. miniDV is considered a consumer and pro-sumer (professional/consumer) format and has become widely embraced in the market place and user communities. For that reason, miniDV is the recommended format for underwater video here. If you’re convinced you want to shoot video in Hi-Definition, HDV is the Hi-Def flavor of DV. However, HDV technology at the pro-sumer level is in its infancy, so choices are limited and expensive.
Low-light sensitivity, resolution, and color depth are next on the list. There is typically less ambient sunlight available underwater as compared to above, so one should look for a camera with acceptable low-light sensitivity. Light sensitivity is usually specified by a camera’s LUX rating in the specification. The lower the LUX value, the more sensitive the camera is to light. However, the method used in computing LUX is left open to interpretation by the manufacturers, so this number can be somewhat useless in comparing cameras of different makes.
Resolution is the total number of pixels (dots) used to define the image. This number seems to keep increasing with every new model of video camera. It’s a marketing game like processor speed is for PCs. Just keep in mind that DV is stored at 720×480 pixels, or 345,600 total pixels per frame. Resolution of three times this (about 1 mega pixel), helps to reduce noise in the image, but resolutions higher than this are pretty much unrecognizable in DV.
Color depth (or bandwidth) is the dynamic range of colors supported in the frame. More depth gives more vivid and saturated colors. This is where 3-CCD (aka 3-chip) cameras outperform single CCD cameras. 3-CCD cameras have a separate CCD sensor for red, green, and blue, instead of just a single CCD for the whole spectrum of color. Color is more true and vivid with 3-CCD cameras, but these cameras cost significantly more.
Camcorder size is another factor. A big camera requires an even bigger housing. This can result in a large and heavy system that’s cumbersome to travel with. However, going for the smallest camera isn’t necessarily the best solution either. Cameras with small diameter lenses suffer from more optical distortion than those with larger ones. A 37mm lens thread is a good choice on the small end of the range. Cameras that are too small also lack enough mass to benefit from the ‘smoothing’ effects of inertia while hand holding the camera underwater.
Finally, camera control and input/output features are very important. The camera should allow for the option to at least lock focus if not switch between full manual and auto focus. Manual white balance capability is a highly desirable feature, although not mandatory. LANC control capability is required by housings that have electronic controls. A FireWire (aka IEEE 1394 or iLink) port is pretty much standard issue on DV cameras today. Just make sure yours has it if you plan to transfer DV video to a computer for editing or DVD authoring.