Whee, more photographical geeking out!
I bought the Canon LA-DC52F lens adapter for my camera (the black tube). It allows me to attach a 52mm filter in front of my camera for special effects, like this Hoya 25A red filter, with two negative strips cut to fit the shape inside:
This was way better than my previous attempts at holding the negatives in front of the lens every time.
The red filter darkens skies and increases contrast (the red channel is more contrasty in most pictures). With the negatives behind it, I could make prettier infrared pictures (this was not color-adjusted):
I then bought the Hoya R72 infrared filter and put it in front of the lens adapter, followed by the red filter. (Putting the infrared filter in front of red filter would be redundant because there is nothing left for the red filter to uh… filter!)
(Picture courtesy of smashpOp‘s Panasonic FZ5 camera. I zoomed 12x on macro mode to make the lens look less big.)
This was a sunny morning, 7:45am.
For both, white balance was set to custom, pointed at the leaves.
I then did a bedroom lab experiment with a infrared-laden tungsten bulb:
For complete geeking out, click here to see a chart of filters in different combinations. 2RI, for example, means light passes through 2 black negatives, the red filter, then the infrared filter. The number below represents the shutter speed the camera used in P mode, ISO 50, manual focus, auto white balance. The reference picture above had a shutter speed of 0.005 seconds; thus, the red filter blocked 1.66 steps, 6.66 steps for anything with the 2 negatives (I didn’t know how to make sense of this), 6.33 steps with filters without negatives, and 5.33 steps for 1 negative. None of this made sense to me; however, it was obvious that 2 negatives gave a diffuse/fogging effect. Therefore, if you don’t mind the fogging effect, film negatives can safely be used instead of the expensive infrared filter. Also, stacking negatives with infrared filters was pointless as it did not affect the exposure.