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Dichroic Color Filters for Landscape Lighting - Guide to Selection, Care, and Use
What are Dichroic Color Filters?
Dichroic filters are circles of glass with a set of coatings that reflect certain colors (of light) and allow other colors to pass through.
For example, a white light contains all colors in the visible light spectrum. If you pass that light through a blue dichroic filter, only the blue portion of the white light passes through while all the other colors are reflected back towards the light source.
The other way to change colors is to use tinted glass filters - these are less costly than dichroic filters but they absorb more light (are less efficient) and tend to fade with time.
Use of dichroic color filters is the most efficient and precise way to change the color of a light source.
How are they Used?
VOLT® sells two families of Dichroic Color Filters
Will They be Bright Enough?
This is an important question. Every color filter (regardless of type) reduces the quantity of light that passes through. There is no way to transform the entirety of a beam of white light into a beam of (for example) green light. A green dichroic filter works by reflecting (back into the fixture) all the non-green wavelengths of light, and only allowing the green portion to pass through. If the initial proportion of green light was only 5% of the white spectrum then the resulting quantity of green light will only be 5% of the original. This is why the more pure (saturated) the color, the greater reduction in perceived brightness. The resulting illumination will be beautiful, but may be less bright than anticipated and require a light source with higher lumen output.
Brightness is also dependent on what is being illuminated. Lighting a tree with dark-colored bark requires a much brighter light than lighting a light-colored object. The most saturated of the filters (such as red, green, and indigo) should only be used on light colored objects.
It is highly recommended that designers test color filters on specific applications before they commit to purchasing the filters for a project - and to use fixtures with high lumen outputs.
Orientation and Insertion
Install the filters with the dichroic-coated side facing the light source.
These filters should only be used in fixtures indicated in the product description page of the specific filters.
Before inserting the filters into the fixture, remove the plastic button on the center of the optics to get a better fit.
Will the Projected Light Show Uniform Color across the Beam
Some of the more saturated color dichroics show color shifts at the edge of the beam – all dichroics have this issue because incident angle of the light source(s) determines projected color.
Wider angle optics exhibit more color shift than do narrower optics since incident angles exiting the filter are wider. Having said this, the color shift (at the beam edges) in most cases is acceptable and may even be desirable since these saturated filters are mostly used to achieve dramatic effects.
If the colors are used for architectural features, then the color shift at the edges may not be acceptable. Always test filters if you are unsure about the effects!
Store filters in a cool dry place individually in their plastic bags - or in a suitable storage case.