Which lens are you happy with now for your infrared work? I know you weren't satisfied with the 24-120, and were looking for something else.
Your answer is actually contained in the 5 photos above. The Sigma 15mm fisheye is awesome (no spotting), as are the 24-120mm and 16-35mm f4 Nikons. The biggest surprise is the 28-80mm f/3.3-5.5G Nikkor that's essentially a cheap, $50 lens I got off of eBay. Not only isn't there any hot spotting to speak of, but the reduction/lack of coating on the elements makes makes it one of the best AF lenses I have in terms of IR light transference. Here's a couple channel swapped images taken with that one.
For the curious, the yellows in the two differ because of different Hue adjustments on the yellow channel. The main thing to notice is the consistency of color throughout the image and the lack of any change in color and contrast in the center.
The 24-85mm has hot spots like crazy. The primes and the 70-200mm f4 are also good, but they are a little warm cutting some of the blues that I get with the "cheap" and old non-AF glass I've tried.
