What is the difference between an infrared filter and an ND filter? I have a big stopper and I would like to take some images to show the infrared spectrum I have seen images where green foliage shows up red and any heat source shown up white §Is there any lens filter recommended for this genre of photography
ND stands for "neutral density" - it is a filter type that (in theory) absorbs all wavelengths of the visible light by the same amount.
Effect of a ND-filter. CC-BY-SA 2.0: Robert Emperley
IR filters filter out all but certain wavelengths - the (near) IR wavelength of the filter. So basically, they are IR-pass filters, not IR-block filters. Thanks @TheLuckless!
As @Hueco states in his comment, IR filters will cut everything below a certain value. That value might be between 650 and 720nm - visible light, however, does go up to 750nm. Thanks for clarifying that, Hueco!
Typical result of using an IR filter. Some effort was put into post-production: The red and blue channels were swapped. CC-BY-SA 2.0: Jannis
What you think of (white heat source, everything else red-ish) is most probably a thermographic camera - they differ from regular cameras in a lot of ways, including lenses that are (typically) made out of Germanium.
Thermographic image. CC-BY-SA 3.0: Lutz Weidner