back alley
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why are they so expensive...not a complaint, just a question...
Roger Hicks
Veteran
As far as I'm aware, because the filtration is via a dichroic coating, not via dyeing.
Cheers,
R.
Cheers,
R.
sevo
Fokutorendaburando
Dyes are not really cheaper - indeed, dyed glass can be decidedly more expensive, so that dichroic filters have taken over in most technical applications where large areas of filter glass are needed.
For imaging use, the bit of bare glass has to be filter coated after polishing - and right now there still seems to be a shortage of production facilities for that, while there are plenty of makers that can polish and AR coat coloured Schott and Hoya panes. I.e. it is a matter of supply and demand.
For imaging use, the bit of bare glass has to be filter coated after polishing - and right now there still seems to be a shortage of production facilities for that, while there are plenty of makers that can polish and AR coat coloured Schott and Hoya panes. I.e. it is a matter of supply and demand.
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It's akin to a circular polarizer being more expensive than a linear polarizer.
http://en.wikipedia.org/wiki/Dichroic_filter
http://en.wikipedia.org/wiki/Dichroic_filter