Re: differences between colorimeter & spectrophotometer
Re: differences between colorimeter & spectrophotometer
- Subject: Re: differences between colorimeter & spectrophotometer
- From: Phil Green <email@hidden>
- Date: Thu, 04 Oct 2001 10:39:45 +0100
- Organization: LCP
Peter Miles wrote:
>
I was very surprised to hear, that for technical reasons,
>
colorimeters were often allot more accurate than
>
spectrophotometers for measuring CRT's with respect to CIE
>
colorimetery.
It's simply that CRT phosphors have very spiky emissions (a large
proportion of energy concentrated into vary narrow wavebands),
especially in red. To accurately record the resulting spectral emission,
you would need to sample at very small wavelength intervals. Most
spectrophotometers in commercial use sample at between 5 and 20nm, but
even 5nm is too crude. We use a telespectroradiometer set to 1nm when we
want to measure the spectral profile of a CRT.
Because CRT colorimetry is based on trichromacy (3 primary stimuli
mixing to produce the full range of colour sensations), the broadband
sampling of a colorimeter does a better job of providing the information
required to compute the CIE tristimulus values.
--
Phil Green
Colour Imaging Group
School of Printing and Publishing
LCP
Elephant and Castle, London SE1 6SB
Tel: +44 020 7514 6759 Fax: +44 020 7514 6772
http://www.digitalcolour.org/understanding