The LEE Filters 100mm System Polyester 25 Tricolour Red Standard Filter is a separation filter.
Maximum transmission above 610nm.
Also used for b/w contrast effects, haze penetration in aerial photography, and removing blue in infrared photography.
These filters are made from a flexible high quality polyester material that is approximately 1mm thick.
They are supplied un-mounted by default and as such are incompatible with the standard 2mm filter slots on Lee Filters holders.
This is to allow them to be cut & shaped to fit alternative applications where a rigid resin filter would not be suitable.
If you do wish to use these filters with the 100mm System Holder then you will need to either purchase a pack of 100x100 plastic filter mounts, modify the holder with 1mm Side Blades, or opt for the Polyester B&W Technical Set in which some of the filters are available pre-mounted.
We would personally recommend the resin filters for most normal use.
Filters are widely used by black & white photographers for creative effect - most commonly to increase contrast between sky and cloud.
However, care should be taken, because as much as a black & white filter darkens one colour, it lightens another - specifically, any colour that is similar to its own.
A red filter, for example, makes a red pillar box appear almost white, and a blue sky as almost black.
However, a red filter also absorbs green, which would block up the foreground of a verdant landscape.
The Black & White filters in the LEE Filters range can be used in conjunction with others, such as the polariser and neutral density standards and graduates.