Topic: Are paperweight collectors a new species?

[tootingpf]

On Kevin and Angela's most excellent Ysart website I was intrigued to see that a Caithness (1963-1970) era Ysart fluoresces Reddish Green under long wavelength UV.

I've long been under the impression that the human visual system can't 'see' reddish green (in the same way that we also can't see a bluey yellow), so I'd be intrigued to see that colour.  Anybody got a picture?  Or maybe paperweight collectors have just evolved that bit further....

[chopin-liszt]

Kevin and Angela's site?
Do you mean Frank's site, which Wuff works on tirelessly too; "Scotland's Glass" ?

The human visual system detects wavelengths somewhere inbetween the longest of the short, red end of the spectrum and the shortest of the long, violet/indigo long end.

We can see red, but not infra-red. We can see violet and indigo, even a bit of ultra violet - but not ultra-ultra violet. The greens and yellow wavelenghts are inbetween those.

So there isn't a problem with seeing reddish green or bluey yellow, unless there's some form of colour bilndness involved.

[Lustrousstone]

Surely reddish green and bluey yellow are just descriptors rather than defined wavelengths?

[chopin-liszt]

Given red and green are percieved from completely different independent wavelengths, as are blue and yellow, yes, absolutely. 

Any other problems are those of perception of the individual and/or the constitution/distribution and ratio of rods and cones in their retinas.
Women do percieve a greater number of colours than men do, in general. More men have varying kinds of colour blindness in general than women do.

[tootingpf]

Ah, I think the 'problem' (if such it is!) is with the visual system, not the wavelengths of light.  There are three colour receptors  in the retina (unless you're colour-blind of course!) - for blue, green and red.  So far so good, but it pretty much accepted now that they feed into two 'opponent' channels.  One can signal either red OR green and the other blue OR yellow (the yellow side takes input from red and green receptors).  Thus you can see e.g. a bluey-green (blue from one channel green from the other) but (supposedly) not bluey-yellow or Reddy-green (that would require the channels to signal two colours at the same time).

That's why I'm genuinely intrigued - I would love to see a colour that could be considered reddish green!  Or bluey yellow for that matter!  Just wondering if the fluorescence gives some odd effect.....

[chopin-liszt]

Then of course, there is the phenomenon of "wearing out" certain receptors by staring at a field of say red for a while, then when you close your eyes you see the shape of the field in green. If it's bright enough, you don't even need to shut your eyes - you'll have the patch of colour in your visual field for a while.

Vision is one of the most complicated things the brain does. It occupies about a third of the brain's volume, and it is not remotely understood yet, science is still scratching at the surface - and the knowledge we have so far would nearly occupy a whole library.

For an example of reddish green, find an image of some Zsolnay pottery with the eosin glaze, I'm going to have a good dig around and see if I can't find a bit of Mdina which is bluey yellow too. I've had a wee look - and found reddy-green bits in Mtarfa.

There are plenty of images of Zsolnay eosin on the web... unfortunately having had a look, mostly very poor photography as far as the colour is concerned!
this one's not too bad.
http://www.ebay.com/itm/Stunning-Zsolnay-EOSIN-Porcelain-BULL-Statuette-Hungarian-Fine-China-/251157225911?pt=LH_DefaultDomain_0&hash=item3a7a2321b7

[chopin-liszt]

I've just had a thought - perhaps the business of seeing reddy-green or bluey-yellow would be a similar thing experientially, as looking at the necker cube? (animation below)

http://www.youtube.com/watch?v=ZUByid1Qfzo&feature=related

[chopin-liszt]

A couple of images which might demonstrate bluey-yellow or yellowy-blue.
The dichotomous experience is far easier to obtain from the pieces in reality than in pictures.

[tootingpf]

Thanks Sue for the pics and the video link! 

The after image thing is evidence for the opponent (B/Y and R/G) channels.  If you stare at a red shape for ages the after image (when you look at a white space) will be green.  Likewise blue will give yellow (and vice versa). As you say, one side of the channel 'wears out' and the other side comes through.

The vases (nice though they are) have blue and yellow swirled together).  No single point is bluey-yellow (no matter how hard I tried screwing my eyes up!).

Sooooooo,  I still maintain you can't see a bluey-yellow or a reddy-green.  Well, that's not strictly true, you can see a blue/yellow mix - it's called green (but that's a different thing altogether).

Anyway, there are some colours you just can't have in paperweights.  It's the law...

Although maybe paperweight collectors CAN see other colours? ;-)

Graham

[chopin-liszt]

As I said, the effect doesn't happen when you're looking at images, you need to be looking at the real piece.
Anyway, reddy-green is brown, and bluey-yellow is green (when mixing pigment).
Red and green are quite distant wavelengtht from each other, while blue and yellow do merge over greens.

I'm sure the phenomenon you are discussing here is the shifting of perception between two dichotomous stimuli - certainly with the reddy-green thing. The shift itself is a conscious mental phenomenon - you're aware of it, and I think that adds a certain piquancy, something extra and slightly delightful to the experience of looking at it. 

I'm not so sure what you mean with your bluey-yellows - because bluey-yellows are the colours I seem to be most attracted to - the effects of silver chloride in glass, and perhaps I look at it so much, just enjoying it, I don't consider whether it is blue or yellow or green, I mostly love that I simply don't know, I don't need to give it a name, I love the experience.

And loads of other folk call green what I'd call blue, or blue what I'd call green.
I know that distinction is purely the individual's choice of label to give it.