Thank you, Barbara!
More on IR-focusing:
I did find that getting to know the lens quirks in IR focusing helps me a lot. Some lens you have to slightly adjust the distance scale closer to you after acquiring focus. How close depends on experimentation, a couple of feet or what I call a very slight twist of the focusing ring. Infinity on the lens is not infinity in IR, again this is a thought on my part.
On my Sigma DP1, I mounted an optical viewfinder on top of the camera just for the purposes of composition alone. The LCD is useless once you mount an IR filter on the lens. I set it manual focus at f/8 with distance at 5 feet with focal length set at its widest setting, the camera is good to go.
Sigma DP1 in Central Park (with B+W 091):
On my Nikon D40x, my go to lens is the Nikkor 18-70. It has a slight hot spot but it makes up for the color rendition and consistency in terms of focus as long as I keep the focus point on an IR reflecting (emitting?) object:
Nikon D40x in Staten Island (with 720nm filter):
On my NEX-3 IR, what is usually mounted is the Nikkor 28mm 3.5 because the lens is such an IR-focus friendly. I set it at f/16 and I am usually ok with hyperfocal focusing technique (set the distance and forget it) even with a very dark filter such as an 830nm.
Here is a sunstar IR output from the manually-focused Nikkor 28mm on an NEX-3 full-spectrum: