Full spectrum photography is something that has interested me since I realized that many of the beautiful photos of space we have come to know and love are really photos from beyond the range of our own eyes. As it turns out, every element has what is called an emission spectra. What does this mean, really? It means that if a cloud of a particular element exists, it will give off very specific colors of light. If we can make a filter to only let through that color, then we can take a picture of only that element. Below is a graph showing different emission and absorption lines.
Taking it a step further, if we have a cloud in space, and it is mostly, say, hydrogen, and perhaps there are some areas that also have some oxygen in it, then we could take a picture emphasizing this cloud if we really only focus on the colors that these two gasses emit! In fact, by isolating the colors of each gas, we could get an image of the space clouds with each gas in a different color! How cool is that!? But, as always, there is a catch to doing this. A lot of the really interesting colors are outside of the range of what we can see with our own eyes.
(Above Photo from Astronomy Picture of the Day)
We experience light as colors, but it is really part of the electromagnetic spectrum, just like the radio waves from a cell phone or the microwave used to cook food. We can measure it’s wavelength just like radio waves as well. Reds tend to be longer at around 700 nano-meters. These tend to cut through the air a bit better than the short wavelengths like blue at 400 nano meters. This is why sunsets are red, as the sun must cut through more air to reach us during sunset. We can see from about 390nm-700nm, which is what most cameras are set to record. Actually, camera manufacturers have to limit the sensors using something called a hot mirror. Camera sensors use a silica chip to turn light impulses into electrical ones. The issue is that they are responsive from less than 300nm to more than 1000 nm. This means that these sensors see light far into the ultraviolet spectrum all the way through visible and well into the near infrared spectrum. If they were allowed to see all of this, the pictures they produce would look awful.
So here is the dilemma; In order to take advantage of these amazing and interesting colors, we have to remove the hot mirror from our cameras, but removing the hot mirror from the camera means the camera will no longer take normal pictures. The only easy solution is to have a hot mirror in front of every lens used with that camera. Recently I bit the bullet and had my camera converted through www.SpencersCamera.com.
The results are interesting to say the least. There is a larger learning curve than I expected for this kind of camera, the main portion being to try out different filters. Not every filter works the same, and it turns out that Nikon used a very specific hot mirror on there cameras. I have been experimenting to try to recover the original look of the D3s while still being able to expand the range when I want it. I hope to be able to showcase some of the camera’s new abilities in the near future, stay tuned!