showstack / glossary / dichroic
Dichroic filter 二向色濾片
A filter that reflects the wavelengths it does not pass, rather than absorbing them. Made from thin interference coatings on glass. Because the rejected light leaves rather than turning into heat in the filter, a dichroic survives sitting in a beam that would burn a gel to ash in seconds — which is why colour-mixing flags in moving lights are dichroic and not gel.
中文
把不通過的波長反射掉、而非吸收掉的濾片，以玻璃上的薄膜干涉鍍層製成。被擋下的光是離開而非在濾片內轉為熱，所以二向色濾片能長時間待在會把色紙瞬間燒穿的光束裡 —— 這正是搖頭燈的混色葉片用二向色而非色紙的原因。
Regional usage
| Where | Term | Note |
|---|---|---|
| UK / US | Dichroic / dichro | |
| HK / TW | 二向色濾片 / 分光鏡片 |
Easy to get wrong
A dichroic works by interference, so its colour shifts with the angle light strikes it. The edge of a beam reads differently from the centre; that is physics, not a faulty filter.
Next to this
Gel色紙A sheet of coloured polyester or polycarbonate placed in front of a lamp to colour the beam. Modern gel is no…Subtractive colour mixing減色混合Mixing by removing light. One white source passes through layers that each remove part of the spectrum, and r…
Sources
- CIE colorimetry and colour mixing fundamentals — International Commission on Illumination primary
Understand the mechanism
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