Quite often when using a standard zoom lens in low light there is just not enough light for a minimum exposure. The 6" Round (mounted) Tiffen LL-D (LLD) (Low-Light Dispersion) Filter can be used as an 85 substitution outdoors in low light when using tungsten based film. With no filter factor, the LLD filter will save you a 1/3 stop over that of an 85 filter. The LLD filter, when used as an 85 substitute will enable the color timer to match the color of a properly 85 filtered original. Be sure that the camera assistant makes a notation of the LLD filter on the slate and camera report.