Infrared Photography
I've been interested in infrared and ultraviolet photography for
many years but never had the initiative (aka budget) to try it with
film cameras. A good thing about digital camera sensors is that they
are just as sensitive to near-infrared as they are to visible light; so
much so that the camera manufacturers have to install a filter to
remove the infrared so that photos will have proper colour and the
camera will focus correctly.
I tried the TV remote control test with my ancient HP 618 camera and
found that it passed, easily seeing the infrared output. I tried a
few tests with crossed polarizers as a primitive IR-pass filter; it
worked as a proof of concept but the quality was poor and exposures
were long. I bought a Hoya R72 filter which improved the image
quality but exposures were still long. The next step would be to
remove the IR blocking hot-mirror from the camera but I didn't want to
possibly destroy a camera I was still using, so I bought the same
model camera for $20 used rather than the $600 it had cost new in
2001. I can tolerate destroying a $20 camera!
After removing the hot-mirror without destroying the camera I tried
the remote control test again. This time the LCD panel didn't just
show the IR LED light up, rather the entire panel flashed white!
That's a sign of how bright a remote control actually is and how well
the hot-mirror does its job at blocking infrared. The sensor needed
to be shimmed after replacing the hot mirror with glass to allow the
unit to focus correctly but once that was done the camera worked
great! Exposure times were normal. The only gotcha is that the
camera is now dedicated for infrared work and would need an external
hot-mirror filter to take visible light photos again.
The most stunning infrared images involve plants and trees combined
with sky or water. Vegetation reflects infrared very well, appearing
bright, but sky and water appear dark.
B/W Infrared
For practical purposes the R72 filter cuts off almost all visible
light. When using the eye to look at brightly lit outdoor scenes
through this filter one can start to see dim images in the deep red as
the eye dark-adapts (but don't look at the sun, the infrared will be
at full strength and burn the retina). Taking photos through a
modified camera means that this dim deep-red isn't recorded by the
camera because of the short exposures needed for the bright infrared
part of the spectrum that the eye can't see.
These images have been desaturated to remove any false colours
recorded by the camera.
False Colour Infrared
Infrared is beyond visible light, by definition, so any colour in a
photo taken through a filter like the R72 must be a camera artifact
created by differences in the way the image sensor's red, green, and
blue filters respond to infrared. The images here have been
post-processed to enhance and manipulate what little false colour was
recorded by the camera. In many cases the result is beautiful.
