Surprisingly enough, a lot allegedly experienced investigators that have
applied with us didn't know what a doubler was when asked about their
equipment. A very basic piece of equipment that every surveillance investigator
should be familiar with.
November 1997
From: JW
To: Field Investigators
Re: Camera Doublers
Another of Ron's excellent articles that we use for training tips;
There are several problems with doublers, once overcome, they
can be very handy.
A moderately priced 2X will eat up nearly four times the
light than the normal camera when fully zoomed out. The light you need for
quality images increases as you zoom in. 4X eats nearly eight times the light
and 6X eats up nearly twelve times the light. Without some light reflecting
through the lens, there is no image to record. The longer the lens, even
"doublers," the more light consumed. Zoom in magnification, consumes more light
than a straight lens. Fine lenses are expensive because they eat up less light.
Many popular "doublers" are 1.2X or 1.4X. The light disadvantage is just past
peak performance and they are useful at twilight time.
Another significant concern, is to make sure the lens does
not weigh ANY more than the lens it replaces. This even holds true for the old
dinosaur camcorders. Just a few extra grams places drag on the miniature
specifically engineered auto-focus motors. The more the "doubler" weighs, the
faster it will overheat, burn out, and lock up the autofocus. This problem is
exacerbated when the "doubler" is made with quality glass. Fine crystal has lead
in it. Plastic lenses scratch easy and have modest optical quality.
Learn to use the features on your camcorder manually. It
makes the weight problem irrelevant if you focus manually. Autofocus is painful
if the camera chases the focus with a moving subject. Client's do not like to
pay for blurs and excuses. The longer the lens, under questionable light
conditions, the closer you get to the subject, with or without the "doubler,"
because you must zoom out until you have enough light getting through the lens
to capture an image. If you are shooting at high noon at the beach, no problem.
With "doublers" it is absolutely essential you stabilize the
camera -- mini pod, bi-pod, tri-pod, or a bean bag, lamp post, and a nylon strap
with velcro strips. Any electronic stabilization features within the camcorder
will be irrelevant, because you are not supposed to use them when they are
stationary unless you like yours in the shop. Learning how to properly use the
equipment solves many problems.
There are good quality lenses, not zoom lenses, that can
produce telephoto results without eating up available light that also weigh the
same as the lens it replaces. Such items are expensive. Many prosumer camcorders
have OPTICAL zooms approaching 20X that are also stabilized with exposure and
shutter controls. Bought out of the back of a magazine from a good company like
B&H, you can steal them at bargain prices.
