Rob Geraghty wrote:
>"Long-pass edge filters"!! - What??Ok. It seems that the optical industry do call these filters 'Long wave pass edge fiters", now that makes a bit more sense, but they're still low-pass filters to you and me.I'd say that it's meant to read "low-pass". Something probably got lost
in the translation either between the technical team and the sales team,
or between the sales team and the web designer.
These multi-layer-dielectric filters have an amazingly sharp cut off, and they're available off-the-shelf in 50 nanometre wavelength steps.
So, what I reckon Colourvision do is this:
They have 7 filtered sensors, in 50nm steps from 700nm down to 400nm.
They subtract the output of the 400nm sensor from the 450nm sensor,
and the 450nm sensor from the 500nm sensor, ..... and so on. This gives
them 7 sharply defined bands, each 50nm wide, across most of the visible
spectrum.
What they do about Infrared, which is always a problem with these things,
I don't know. It would seem more sensible to use high-pass filters, and
automatically chop off the IR.
Anyway, this is definitely NOT the way that the human eye works.
The human eye has only 3 colour sensors, with nearly 100% overlap in
their spectral responses.
Still, it seems like Colourvision are giving a lot of technology for
the money.
Whatever you do, don't try to read their FAQs on colour management though.
They seem deliberately designed to confuse, and to make you think that
colour management is impossible without their help.
Another time-honoured advertising ploy, eh Rob?
On the other subject:
Doesn't a neutral density filter have grain?Nope. Well, not at any magnification short of an SEM.
It's a pure dye colouration of a plastic film, or a dyed gelatin coating.
I used ND filter gels to check out the Dmax of my scanner, and that's when I noticed that a lot of the 'noise' wasn't noise at all.
Regards, Pete.
