Working with Digital Cameras
Checking the NIR sensitivity
The way to measure your digital camera's
NIR sensitivity is the same as with a camcorder.
The higher your camera's
NIR sensitivity, the brighter TV remote controller's transmitting lamp
will appear on the LCD screen. The other way to measure the NIR sensitivity
is the camera's equivalent ISO film speed. The ISO is a term used for representing film
sensitivity and generally used in digital cameras instead of "minimum
ISO 100 is standard and the higher the number, the greater the
sensitivity, and vice versa. Therefore a film speed of ISO 200 is
twice as sensitive as ISO 100, and half that of ISO 400. Please
check your camera's manual to see the ISO speed.
Taking see-through pictures with
an unmodified digital camera
It is true that the CCD sensors of digital
cameras are also sensitive to the NIR. But as shown in the Experiments
digital camera's see-through pictures are not as acceptable even in environment
A. To get acceptable pictures, slowing the shutter speed down manually -
often up to 1/8 or 1/4 second - is needed in most digital camera models.
Therefore some camera models where shutter speed can't be adjusted
manually or can't be
adjusted lower than 1/60 sec (for example, 1/8, 1/4 second) can't
take see-through pictures at all without modifying.
The problem is that slowing the shutter speed down manually
is not suitable for moving objects. This is because the slow shutter will give moving
objects a very blurry look. Thus, an unmodified digital camera can be a good see-through device for
fixed objects but is not desirable for moving objects. To get acceptable see-through
images of moving objects, you need to
modify your digital camera.
Another problem is that some digital camera models
fitted with the PF only show up
quite dark - sometimes not visible at all - images on the LCD
screen. If you have one of these models, it just means you won't be able to verify the
see-through picture until you transmit it to your computer.
in modifying a digital
A modified digital camera will allow you to get
good see-through images under any NIR environment. Since slowing the
shutter speed down is not needed in a modified camera, moving objects
can be captured. However, the problem is
that modifying a digital camera is often much more difficult than
modifying a camcorder, as described below.
As mentioned in the Normal
Camcorder section, the purpose of modifying a digital camera is
also quite clear and simple.
You just need to remove the ICF installed in-between the optical lens
and the CCD. However, some models, especially the early digital camera
models, don't employ an independent ICF owing to digital cameras' compact
internal structure. Alternatively, by coating an optical lens' surface with infrared-blocking chemicals, these models get the same infrared blocking
effect as employing an independent ICF. These coated-lens ICFs not only have an infrared blocking effect but also an original optical
effect and so this coated-lens ICF must not be removed. If you
remove this coated-lens ICF you will get terribly blurred images.
So, you need to confirm whether the ICF is an independent ICF
or a coated-lens ICF. These two can be easily distinguished by surface shape,
rather than colour.
An independent ICF has flat surfaces on both faces. On the other
hand, a coated-lens ICF has curved surfaces on both faces or one of
the faces as shown here:
Since a camcorder has enough inner space to insert an independent
ICF, most modern camcorders don't employ the coated-lens ICF method.
For them, this is less cost effective. Contrarily, many early
digital cameras or industrial color CCD cameras (especially compact-type,
colour pin-hole cameras) have employed this coated-lens ICF
However coated-lens ICFs often bring a slight distortion in
the edges of images owing to uneven coating of chemicals, especially in
the edges of the optical lens. So the latest digital camera manufacturers
tend to employ the independent ICF method which is used in camcorders.
you can't be sure
your camera has a coated-lens ICF or an independent ICF until you
open up your camera's case.