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Did you know…?
Just because a lens can be mounted on your camera, it doesn’t mean it will function the way you expect it will.
When you use a lens designed for a different format from the one you are using, there can be a dramatic difference in the effective focal length. It is dependent on the diagonal of your imager. A 2/3” imager (be it CCD or CMOS) has an image circle (and therefore diagonal, also) of 11mm. That also means that a so-called normal lens for that format would be 11mm. Take that “normal” lens off of your 2/3” camera and mount it on a camera with a ½” imager (with a imager diagonal of 8mm) and you will obtain an increase in effective focal length by a factor of 1.38X. In other words the lens now becomes more telephoto! Take that identical lens and put it on a 1/3” camera (with a imager diagonal of 6mm) and you will increase the effective focal length by a factor of 1.83x.
If you take a lens designed for a ½” imager and put it on a 1/3” camera, the effective increase is 1.33X.
Optical conversion adapters, which go between the lens and camera body exist, but they are expensive--and will have a small, but significant “light penalty,” as will just about anything that places the main lens further from the image plane. These adapters range in price from about $800 to $2500.
If you adapt old 35mm still camera lenses to your 1/3” 16:9 HDV video camera, the conversion factor is a whopping 7.2X. That makes even your widest angle lens an extreme telephoto!
Oh, another important point to remember when changing lenses: always adjust your back focus and perform a shading adjustment (see your operating manual for details). If your back focus is out your lens won’t focus properly during zooming.
Improper shading may reveal itself as color blotches, especially on scenes with white or light-colored content. Not something you want deal with in “post.”
By the way, if you can possibly avoid it, do not use lenses designed for standard definition on a high definition camera. They do not have enough resolution (measured in line-pairs per millimeter), and they may not function so well in HD’s wider 16:9 format. If you must shoot with a SD lens, use it for close-ups and possibly medium shots. Neither require as much resolution.
Finally, in closing, keep in mind that the videographer who “resolves” never to break an optical law, will more than likely keep out of trouble.
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