Quote:
Originally Posted by Aussie Bloke
This stamp has very very nice emerald green colour too it but comes up as more of a yellowish green when scanned! And with aqua colours they don't show up as a nice strong blue green on a computer monitor either.
I can imagine that 12p stamp if displayed on a 15GP22 CRT would come up with its original emerald green coloul. This would be a good experiment for CT-100 owners to try out, displaying a 12p queen head stamp on their sets and see if they can see the original emerald greens.
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There are several fine points to this experiment. When you use a scanner without any special setup, it and the softwaree you use for photo-editing and viewing is normally setup for the modern phosphors, "sRGB". In this case, even if the scanner is capable of correctly sensing the color, it is adjusted to fall within the sRGB gamut. Programs like Photoshop can be set to operate in the NTSC or even larger color spaces. However, your scanner may not be adjustable to operate this way. Digital cameras used in "raw" mode can produce a raw file that Photoshop can then import and process in NTSC color space. An NTSC picture displayed on an sRGB monitor will appear desaturated and with an exaggerated range of hues between red and green [caution, that is a simplified statement]- but if the RGB outputs could be sent to a 15GP22, not only would the colors be correct, but the emerald green would be correctly reproduced.
An important point is, if the range is limited at any point of the end-to-end system, you cannot get it back. Also, if the scanner/camera doesn't sense the dyes the same way as the eye, you will never get the right result even if the device is capable of an extended range.
The main reason that CRT displays with yellower green came into use is that brighter pictures were much more appealing to buyers than dimmer pictures with the wider range. Today, common flat panel displays (for example computer LCD monitors in the few hundreds of dollars) have a range similar to sRGB. (However, they are not always specified to even do that - laptop displays are typically worse.) Some extended gamut displays are being manufactured, both for computers and HDTV, at higher prices. These usually are LCDs with LED backlights or other special technology to get purer spectra for the primary colors.
As another note, diagrams of the range of colors on the 1931 CIE diagram distort how much gamut is lost, exaggerating the loss in the green region and under-representing it in the blue region. The NTSC blue is actually quite a bit less violet and more cyan than the modern blue, and this reduces the saturation of purple and magenta colors similar to the way the modern phosphors limit cyans and true greens. This comparison is better viewed in a "Uniform Chromaticity Diagram" or even a 3-dimensional "L*ab" plot.