While we had the K20D we got the chance to, briefly, see how it handled infrared photography
The K20D is a great camera but, in the short time we had it before we needed to send it back, I was very curious to see how it handled IR photography. To this end we went out with the camera, a couple of lenses and a Hoya R72 filter.
First thing is to establish the exposure. Auto exposure did not work. So I started a sequence of exposures at 4 seconds.
If you examine the histograms above you can see that about 8 seconds is right if you are going to use the red channel only, whilst 30 seconds or a bit longer is right if you will use the green channel for your conversion. Notice that unlike many cameras, the green and blue channels have significantly different exposure needs in IR.
Picking 15 seconds as a compromise, here are the individual channels and the best image with processing using that channel only:
Next we looked at image noise with changing ISO. These are 100% crops from the center of the RAW image. The exposures started at 15 seconds and shortened by a stop each time.
Here are some individual channels from the varying exposure tests, processed to give a good tonal range.
4 second red
8 second red
15 second red
15 second green
30 second green
As you can see, the K20D is very capable in IR provided you do not mind the long exposures and can give enough exposure to keep the noise low.
An Impressive camera.
You can see our visible light tests of the Pentax K20D here.
If you are after a K20D I can recommend B&H Photo in NY, our preferred US camera equipment supplier.
The Hoya R72 filter can also be purchased from B&H Photo.