The Leica E67UVA/IR Glass Filter is specifically recommended for the Leica Digital M8 camera. In order to maintain maximum optical clarity, the M8---with its superior sensor---was not designed with a total IR protection filter system.
This filter is designed to eliminate the pinkish/purple/reddish tint that certain black synthetic items might be subjected to when shooting under certain lighting conditions, such as that of incandescent bulbs. This filter can also serve to help protect the glass in your lens.
Leica recommends removing the attached UV/IR filters when using lenses from 16-50mm in analog photography