Kodak/Wratten 87 Range
Cheap but effective filters.
These filters are often used by people wanting to "try out" infrared filming. This is simply because they are typically easier to get and very much cheaper than many of the other makes.
There are four types in the 87 range. These are the 87, 87A, 87B and 87C. The 87C is the most popular one because it performs very well and is still produced by Kodak whereas the 87A and 87B are no longer produced and are therefore somewhat rare.
The 87 is also currently produced though given the choice, the 87C is better suited to infrared x-rays.
The filters come in the form of a 75mm x 75mm square of gelatin which is very thin and flexible. All you have to do is cut out a circle to the size you require and insert it behind a clear glass or UV filter (such as the Hoya Skylight 1B). The UV filter has no effect whatsoever on infrared filming and is usually very cheap and easy to get from most camera shops.
The filters have different transmission characteristics and are shown below for comparison
This indicates that the 87C and 87B are ideally suited to infrared x-ray filming under most conditions with the 87B having an advantage in brighter sunlight. The 87B being a reasonably close match to the Hoya RM90.
The 87A is a close match to the Heliopan RG1000 and the Hoya RM100 and shows best results in bright sunshine.
The plain 87 is a less suited to bright outdoor conditions and is similar in characteristics to the Tiffen 87. Filming can be done in sunlight but typically requires more careful control of exposure.