On NTSC Video, Blue Blurring, Chroma Subsampling

NEOGEOman writes "Something I've been fascinated with for a long time is video signals. On my website I've spent over six years collecting video and other hacks for game consoles. I've recently put together the fourth revision of my video signal primer and it's expanded to six pages now, including strange subjects like chroma subsampling, horizontal colour resolution and rather interesting revelation: your eyes suck at blue."

Comments

Girl

[Anonymous Coward]

who's the girl? She's hot ;)

Obvious Physics

[rbruels]

If NEOGEOman had bothered with a freshman-level physics or astronomy course, the conclusion that "your eyes suck at blue" would have been obvious some time ago.

It's well known; as our eyes drift to the blue and red end of the spectrum, we lose our sensitivity, off by many orders of magnitude from say, yellow. This is why you see blue, and more commonly, red, lights as "night" light sources.

The general reasoning: our eyes evolved with a single primary light source: the Sun. Which has quite the yellow tinge to it. Our eyes adapted to this, and as such, gave yellow the highest sensitivity and drifted off in a rough bell curve from there.

It was an interesting article, and certainly put the RGB sensitivity into perspective, but ... it's not entirely new or surprising, either. Nor does the human eye really respond at RGB -- its response curves (beta, gamma, and rho) more closely correspond to blue, green/yellow, and yellow/orange.

That all being said, thanks for letting us meet Traci. ;)

Re:Obvious Physics

[Anonymous Coward]

You have been misled.

It is in fact BLUE at 445nm that the eye is most sensitive to. Blue receptors are the most sensitive.
This "sucking at blue" thing has nothing to do with sensitivity of the receptors, but with the fact that only 2% of the cone receptors are the blue sensitive ones, so you have no resolving capability in the blue part of the visible spectrum.

This is an issue of resolution NOT sensitivity.

Furthermore, I have been researching vision for about 10 years now, and I can tell you that the curve you linked to is totally fucked up. The leftmost curve is not far enough to the left at all. 445nm, which is what your blue cones are sensitive to is far more purple than that stupid graph would have you believe.

You need more reputable sources.

Re:Obvious Physics

[NEOGEOman]

I actually chose this image because it was more or less neutral, with a primarily white/grey image. All the other images I have of Traci have far, far more flesh colours in them. ...

I've said too much.

Re:Even better reason...

[Anonymous Coward]

What about blueberries and smurfs?

It's due to wavelengths

[SirNarfsALot]

You have to focus on different colors differently because red, green, and blue light are all different wavelengths and therefore are refracted slightly differently by your eye (shorter wavelengths, i.e. blue, refract more, longer wavelengths - red - refract less). You have to focus closer in on a red light than a blue light for it to be sharp, if you can even do so.

Something I don't understand is that blue light seems to exaggerate my mild astigmatism; I have a Logitech mouse that drives me crazy if I try to focus on the blue taillight. Red lights I can focus on quite clearly and from further away (I am also nearsighted) than any other color lights.

Fun related trivia bit (and forgive me if this is common knowledge):
If you have a decent old 35mm SLR camera with a normal lens (other lenses may have this too) look at the focus ring. There is a marker for where to line up the focus ring in normal conditions, and then there should also be a little red dot a fraction of an inch to the side of it to show where to line up the ring when shooting on infrared film. You have to focus the lens closer for infrared than for visible light, because longer wavelengths refract less.

This is all related the prism rainbow effect, too.