Like the past summer, 2014 was a bad year for fires in Canada. Very Bad. Most of western Canada was covered by a thick haze in the sky for almost two months from fires in the Northwest Territories, British Columbia, and Alberta. The smoke reached as far east as Ontario, and as far south as Kansas.
I had only had a full spectrum camera for a year at that point(not my current camera, but an older converted Panasonic Lumix DMC-Sz7), and was still learning how to use it to the best effect. On a flight over the prairies, I experimented with taking photos out the aircraft window. I was surprised at the photos. They were incredibly clear, picking out details on the horizon that I couldn’t see with the naked eye. The haze was gone. Take the photos below- the top is in the visible range(taken with a normal Canon Rebel T3), the bottom is with my full spectrum camera with a 760 nm infrared filter.
It turns out that the longer the wavelength of light, the less effect smoke and haze have. This can be seen even in the visible range, by separating the colour channels of the photograph(most photo editing software will allow you to do this).
Here’s the same visible spectrum photo as above. The shortest wavelength channel(blue), shows the most scattering of the light. Blue light is about 45o nanometres.
The blue channel by itself renders the scene completely indiscernible. Other than the black silhouette of the airplane window frame, the scene is completely grey. As you know what you’re looking at, you may be able to see the horizon.
Down to the Green Channel. Green peaks at about 550 nm
The green channel is clearer, but still not a good photo. The horizon can be seen no, as well as farmland in the foreground.
The Red Channel(peaking at about 600 nm) is clearest.
If you look hard, Ponds and rivers can be seen in the farmland, and even roads can be distinguished from the fields. For a normal camera, this channel is definitely the clearest.
But… lets look at the Infrared photo one more time.
I took this photo about 10 seconds after the visible photo, so the foreground has shifted slightly. Still, there is no doubt that this is the best photo.
By the way, Ultraviolet light(<400 nm) is scattered even more than blue light. I rarely take UV landscape photos for this reason( although I will post some in the future). Even on a clear day, UV photos look very hazy. That is also why UV filters work to improve a photo: they eliminate the small amount of UV light that affects the camera sensor, making th photo slightly less hazy. At the time, it was academic, as my Panasonic camera was not able to take UV photos. If I had another chance, I’d definitely take a UV photo on the flight for comparison.
Okay, one more example before I leave. This is from the same trip. The order of the photos is the same as above: visible spectrum, followed by blue channel, green channel, red channel, and infrared. I’ll give the visible spectrum a better chance this time by boosting the contrast. It wasn’t this clear to the naked eye.
Red puts up a better showing in this photo, but infrared is still the winner. The only thing to point out is that the blue channel photograph may be actually better at showing the river than the green or red channels. This is mainly because the river is reflecting the blue sky. I did try taking photos deeper in infrared with my 950nm lens, but between the airplane window and the low sensitivity to light that deep in infrared, the photos(although clear) were blurry from turbulence and a long exposure time.
Since 2014, I’ve used infrared much more often on hazy days, and haven’t been disappointed.
Parallel Views 