Moire Issues

[Graeme Nattress]

"We do see aliasing on stuff that moves " Can't say I've seen that myself - care to elucidate? Is that spatial (which is what I'm on about) or temporal aliassing?

Graeme

[jbeale]

You can get temporal aliasing (rotating objects seem to stop or move backwards, etc.) if you have a fluorescent light, strobe light or any other light that turns on and off, but I don't understand how spatial aliasing (moire patterns) happens with your naked eye unless you are looking at a scene through a screen door, grille, cloth etc.

In theory, since your eye's retina is composed of discrete photosensitive sites it could have aliasing, but the rods and cones have no fixed pattern, and besides your eye is in nearly constant motion. I'm curious in what situation you could possibly see spatial aliasing.

[Graeme Nattress]

And the brain has fantastic image algorithms!

Graeme

[Jared VanLeuven]

And the brain has fantastic image algorithms!

Graeme

This came to my mind the other day as I was driving along and noticed the wheels of a car in the lane next to me. Its wheels (spokes) looked like they were moving backwards, as in the same effect that you can notice on film. I wondered what our eyes' refresh rate is?

Oh, and no, the wheels in question weren't those funky spinners... :)

[Graeme Nattress]

Yes, that's temporal aliassing.

The brain is funny too though, with optical illusions and the like!

Graeme

[Jeff Kilgroe]

I wondered what our eyes' refresh rate is?

I wrote a paper on this topic (or just how digital imaging compares to our eyes and brain) back in college. I researched and researched and at the time (nearly 10 years ago) there just wasn't much to be found. There is just so much about the human brain and our nervous system that is still a complete mystery. One of the most fascinating pieces of information I dug up in my research though was a study done on the human eye and color. I can't recall the details of the conducted by who and when or where. But they used cards with color gradients in red, green, blue, white to black, yellow, purple, orange, etc.. In an attempt to determine just how many shades of color the human brain could differentiate. What they found is that it varied drastically from one person to the next and results for males fell within one range and female results were in a slightly different, but identifiable range. But the general consensus was that the human eye can differentiate over 2000 shades of grey, nearly 1500 shades of red, 2000 shades of green and 1200 shades of blue. Human vision is essentially 4-channels, Red, Green Blue and Grey. ...The study also found that a small percentage of individuals (just a few percet like 2-3%) of those tested had vision ranges that shifted slightly into the infrared portion of the spectrum. These individuals tended to be more sensitive to various "fluorescent" colors and could see more tonal ranges where most people just saw something white. They also found that many people are blind or not sensitive to certain tonal ranges. So they may be able to see levels in a red gradient up to a certain point and then several spaces on the chart would appear as a solid color tone before it began to look like a gradient again. It was fascinating, but I can't recall much more than that.

Our eyes also don't have a "frame rate" But it seems that our brain samples the rods and cones within our eyes individually and in a semi-random order with the ones near the center of our eyes firing more rapidly. I don't recall ever reading anywhere as to what the actual "sampling rate" or "refresh rate" of the rods/cones in our eyes actually is... Or if anyone truly even knows.

[Jared VanLeuven]

Fascinating stuff, man.

I guess they'll figure it out the day we get our movies delivered straight into the optic nerve. :)

[Jeff Kilgroe]

I'm waiting for the day I can dump my thoughts/dreams directly to physical media and edit them in real-time. :D

[ericyoung]

This came to my mind the other day as I was driving along and noticed the wheels of a car in the lane next to me. Its wheels (spokes) looked like they were moving backwards, as in the same effect that you can notice on film. I wondered what our eyes' refresh rate is?

Oh, and no, the wheels in question weren't those funky spinners... :)

Hmm. The only time I've seen this in real life is in the dusk/evening when the strobing streetlamps will cause this. What time of day did you see this?

[Jared VanLeuven]

It was daytime. I thought it was odd, myself. My first brush with that effect was as a kid watching "To Fly" at the Smithsonian Air & Space Museum in the scene with the old car. Funny how things like that stay with you.