Re: Spatial frequency (Should be: color spectral evaluation)

Dear Samuel,

you may answer your question by taking a closer look at what RGB 
really means and how such signals come into existence in your camera.

> can a ImageJ read a RGB photo (taken by a cheap USB Camera) and filter it to
> show only the colors between 2 wavelengths (say between 465 and 495 nm, this
> is useful for filtering based on emission and excitation spectra of
> Molecular Beacons) or do I need special cameras which are spectrally aware,
> to capture and anlayse this information, thanks Samuel, Virologist India

In fact your color camera has tiny color filters on top of its light 
sensitive elements (pixels). Most often, half of the elements are 
covered by green filters and the remaining two quarters are covered 
by red and blue filters respectively. These three filter types show 
more or less overlapping spectral responses with peak transmissions 
-- of course -- in the green, red and blue.

If you need high color spectral resolution you may use a spectrometer 
type camera or a b&w-camera together with appropriate interference 
filters.

Best
--


                  Herbie

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         <http://www.gluender.de>