There are a lot of DOF lens converters in the market to achieve a shallow DOF. But all of them are expensive. We have an old Canon EOS camera. Can I just remove the 35mm lens and attach it to the front end of the XL1 lens to achieve shallow DOF? Thanks.
Long answer... using a 35mm lens on a camcorder by itself does not decrease the depth of field. The DoF is very deep on a small camcorder because of the size of the tiny 1/3" sensors. It's principals of physics and optics that really can't be bent much... the smaller the "target area" of the image, the greater the depth of field will be. This is why small camcorders have somewhat deeper depth of field that bigger "full sized" cameras, which have 1/2" or 2/3" sensors (but even the bigger camera have very deep DoFs). The same principals apply to film: 35mm film has much shallower potential DoF than 16mm because the surface area of the frame size is about five times bigger (and just for comparison, a 16mm film frame is going to be roughly the same size as a 2/3" video sensor).
This is why you gain no change in DoF by just changing to a 35mm SLR lens. You must use a lens converter (which basically projects the image onto a 35mm-sized groundglass and re-photographs it) to achieve shallow DoF.
Yes, some of them are expensive. The "Rolls Royce" of lens converters is the P+S Technik Mini35 (for small cameras) and the Pro35 (for bigger cameras). Yep, they are expensive, about $10K-ish for the Mini35. On the other end of the spectrum are the bargain converters such as the Letus35 (just a few hundred bucks) and the Brevis35 (a little more than a grand, with lens mount). Somewhere in the middle (actually more toward the cheap end) is the unit from Redrock Micro.
I will say that having played with several of them (and am owner/user of a P+S Technik) you seem to get what you pay for. The more expensive units just seem to be better designed, more functional, and work better than the cheaper ones (I must say the Mini35 that we have is one of the best designed and built pieces of equipment that we have ever bought). On the cheaper end though I have seen some very nice footage out of the Brevis35, which is quite inexpensive.
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What SLR lens will I use so that when I shoot close up (from top of head to shoulder) I will get an even focus of the whole head? I think I read it (also from you, Todd) that when I shoot with 50mm at that distance, I'll blur the ears if I try to focus on the nose.