There's a company that used to make a plastic screen backdrop that
would soften backgrounds - I always wanted to try it but never got
around to it.
The only other thing I can suggest is to use the
sharpest possible lens. With a 2/3" camera, you can get cine-style
lenses that are better in several ways than a standard ENG lens.... They
have prettier bokeh, and I have found that they appear to have
shallower DOF than a cheaper lens.
Technically they don't ... But
they ARE sharper. So if you are shooting wide open, and the part of the
image that's in sharp focus is extremely sharp, you notice the fall-off
in focus more than you would with a lens that isn't as sharp to begin
with. I've never confirmed this scientifically but it sure seems to work
- although nowhere near as much as using a larger sensor does.
Unfortunately
if you are working with 1/3" and 1/4" sensors there is really not much
you can do, except live at the extreme telephoto end of your lens (which
probably comes with some sacrifice in other aspects of image quality)
No, not really. Depth of field is an optical property determined by your aperture and image (sensor) size.
You
are more likely to get a good blurred effect by trying the long end of
your zoom. Zoom in all the way, then you move as far back as you need to
frame the person. Make sure that there is nothing directly behind the
person and that the background is much farther than the person.
[It
technically depends on how the aperture changes with focal length
(every zoom is different, and some are designed to be constant
aperture), but the way most zoom lenses work, you're likely to get more
subject isolation effect when operated as far at the long end as
possible.]
You may also be able to fake shallow DOF effects using
various techniques, such as printing a blurry poster to act as a
background, or using a UV filter and smearing vaseline over the parts
you want blurry, though this does not work for moving subjects like
people. (Sounds crazy but I did that in the days when I only had the
money for a P+S.)
The size of the sensor does not create the
bokeh. It is created by the lens. The only affect of a smaller sensor is
that it crops the image.
I will also note that bokeh at the
center of the image differs from bokeh at the edges of the image (look
at the MTF charts for your lens, which compares the differences at the
center of the lens to those at various distances from the center). Most
lenses have differences in the bokeh toward the edges which, depending
on what you are looking for, may make a better or worse image from a
bokeh perspective.
There are plug-ins and methods for creating a
bokeh effect within a sharp image, e.g., onOne's Focalpoint. I do not
know if a similar capability exists for movie clips (I work with stills)
but I suspect one does.
Just remember that a 25 mm lens is a 25
mm lens is a 25 mm lens. It will always have the same DoF at a given
aperture (technically a tiny bit more or less if used on film vs.
digital, digital being more critical), but it will have different PoV
depending on sensor size. So if you want the same DoF achieved with a 25
mm on a 35 mm size sensor, you can just slap the same lens on your
1/3". It will now be a much tighter PoV, but the same DoF at the same
distance. Of course in practical terms, this means it's hard to achieve
what you ask because you would now have to move further away from
subject because of narrow PoV, which would give you greater DoF again.
EDIT:
Helen Bach makes important remarks in her comment. DoF will differ if
your image from a smaller sensor is enlarged to the same size as the
image from a larger sensor. This is usually what happens to a video
image. Read up on circle of confusion for more info about this
parameter. Still, this is a good rule of thumb, and important to
understand.
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