The Tiffen #4 Viewing Filter is intended for process photography. Balancing lighting by eye is a matter of experience.

Decisions can be made easier by using contrast viewing filters.

These are designed to handicap the eye, with its much wider range of apparent densities, to resemble the range of different types of film.

Use contrast viewers to judge the relative densities of highlights and shadows

There are viewers for black-and-white films, as well as various densities of viewers for colour films

A darker viewer is used for slower film speeds, where you would tend to use brighter lighting; faster film, which can be used in darker environments, would require a lighter viewer


Tiffen Viewing Filters
-The #1 is for black-and-white imaging
-The #2 viewer is for film speeds up to 100
-The #3 is for faster films; they can also be used for video, with the #3 being better suited to lower light levels
-The #4 green viewer is for process photography
-The #5 blue is for blue screen work, as well as for adjusting colour video monitors