Some manufacturers use their own designations to avoid this confusion, for example Singh-Ray has a warming filter which they designate A‑13, which is not a Wratten number. Filters used where precisely specified and repeatable characteristics are required, e.g. for printing press color separation and scientific work, use more standardized and rigorous coding systems.
Some manufacturers use their own labels to avoid confusion, such as Singh-Ray's A-13 warming filter, which is not a Wratten number. Filters used for precise specifications and repeatable characteristics, like those in printing presses or scientific work, utilize more standardized and rigorous coding systems.