I have explained in previous posts that Infared photography can be undertaken via the use of infrared film, filters or a converted camera.
These days infrared filters can be obtained fairly inexpensively on the internet, and some companies (such as Neewer, whose IR lenses can be purchased through Amazon) produce sets of filters to allow through various wavelengths of infrared. The most popular infrared filter would be an IR720, which produces photographs of a resolution comparable with conventional photography. The higher numbered lenses let in more restricted wavelengths and the results get progressively grainier and more impressionistic.
This photograph was taken with an IR850 filter.
If you do decide to buy a set it might be a good idea to buy the largest thread setting for your lens collection, which will allow you to use stepping down adaptors on a larger range of lenses.
The other thing to note about using filters is that one will need a tripod and a long exposure. Exposure is not easy to determine and is often a case of trial and error, but the results can be very worthwhile.
This shot was taken out of my window, and I really like the extreme grain which still manages to resolve itself into a recognisable image. I will need to experiment more with this.