Another alternative was to make a drop through filter that consisted of the three coloured gels and two opaque sections that is literally dropped through a filter holder during exposure.
12.
"Drip brew coffee, " also known as filtered coffee, is made by letting hot water drip onto coffee grounds held in a coffee filter surrounded by a filter holder or brew basket.
13.
However, a " simple polarizing " microscope is easily made by adding inexpensive polarizing filters to a standard biological microscope, often with one in a filter holder beneath the condenser, and a second inserted beneath the head or eyepiece.
14.
In general, square ( and sometimes rectangular ) filters from one system could be used in another system s holders if the size was correct, but each made a different system of filter holder which could not be used together.
15.
Most of Cokin's filters are made of optical resins such as CR-39 . A few round filter elements may be attached to the square / rectangular filter holders, usually polarizers and gradient filters which both need to be rotated and are more expensive to manufacture.
