Yes, if one lens lets you open the iris wider at a given focal length you have the possibility of achieving a shallower DOF.

the 16x isn't a tad faster at the long end, it's a LOT faster

You can map out the DoF for your camera with a tape measure:

Fully extend and lock the tape measure, position it so that it measures the distance from your camera to the end of the tape measure.

put the camera on a tripod and position it so that you can set the end of the lens right at 0" and tilt it so the tape measure runs across (top to bottom, left to right...whatever) the frame.

set the iris wide open and zoom all the way out.

Start with the focus as close to the camera as you can get it, check the tape measure in a field monitor or big tv. As you focus out, note the begining and ending of the sharp focus areas.

Zoom in to 25%, repeat the procedure
50%
75%
100%

You will be able to see the differences in the DoF at different zoom levels. Chart them and keep the graph in your camera case for reference!

There's also DOF charts for any given format size, just find or print a 1/3" widescreen chart, it'll tell you what DOF to expect from any given aperture/focal length.

You CAN get a very tiny DOF with the 16X or 20X but it is conditional. If you use the lens long (from 8X and over), if you keep the aperature WIDE open, if you bump up the shutter, etc. I have shot a few things that people thought were mini35 with the 16X manual. Just have to looks at your tools and work backward with your production...



ash =o)

Ash,

I've shot a couple of interviews from the next room... litterally. I was in an office, interviewing a director, and wanted a nice shallow DOF. So I put the camera in the receptionists office, shot through the doorway. They thought it was a bit funny, but the end product looked great.

For some reason that made me have a vision of Orson Wells having a fit and chopping at the studio wall with a pickaxe into the executive offices so he can get the DOF effect he wants from the studio executive's bathroom onto the set.

Matthew,

Nothing so drastic as that! But I will say this, when using the long end of the 16x for a talking head interview, to get that shallow DOF... the camera sits pretty far back. This can actually be a great thing, in terms of setting up intimacy between the interviewer and the talking head. Because the interviewer is sitting up close, but just out of frame, and the subject is usually looking at the interviewer, the camera is so far out of their field of view, it can become 'invisible' to them. Great for intimate subjects and genuine responses.