a try at that Spanish Castle thing
Jun. 8th, 2006 11:38 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
eub(Shocking-to-me perceptual trick ganked from here.)
I gave it a try and mine sort of works; the indefinite persistence is there, but it doesn't manage full color saturation. It might just be my choice of source image. I could try oversaturating my inverse-color image, but it would clamp very soon. I simply set the inverse-color image's luminance to 50% everywhere; I didn't check to see if that's what the "Spanish castle" one did.
What I'm really fascinated by is what characteristic of the grayscale information of the image is needed to make the color afterimage persist. It can't possibly work with a flat gray field, right? But it does work with the castle's sky. So maybe it works with a grayscale gradient, or with a flat area alongside something else in the frame. I should try some of those.
I gave it a try and mine sort of works; the indefinite persistence is there, but it doesn't manage full color saturation. It might just be my choice of source image. I could try oversaturating my inverse-color image, but it would clamp very soon. I simply set the inverse-color image's luminance to 50% everywhere; I didn't check to see if that's what the "Spanish castle" one did.
What I'm really fascinated by is what characteristic of the grayscale information of the image is needed to make the color afterimage persist. It can't possibly work with a flat gray field, right? But it does work with the castle's sky. So maybe it works with a grayscale gradient, or with a flat area alongside something else in the frame. I should try some of those.
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no subject
Date: 2006-06-09 06:46 pm (UTC)--as beaq mentioned, a lot of high-contrast areas, where a little color goes a long ways
--A great way to accompish the above is to choose an image in which the center of focus is surrounded by a low-detail (low value contrast) field of a complementary hue. The castle image uses this technique with the amber hue of the stonework contrasting with the blue of the sky. This makes both colors stand out better.
--The greyscale image should have a lot of high-value (whiter than medium grey) areas of color; the since you cannot move your eyes from the dot, it is only the lighter and brighter (high-value, high-saturation) areas that will be visible in the peripheral areas.
--Important: the dot should be on the center of focus (high-contrast/detail) for the picture, otherwise your eye will be drawn away from the dot, destroying the effect. Strong colors, especially reds, will attract focus and should only be used carefully: if reds are used, keep them near the dot.
--keeping the previous point in mind, the dot should still be close to or at the center (as you have done); an consistant amount of periphery is less likely to draw the focus away from the dot.
complementary color pairs in RGB: blue/amber; purple/green; red/aqua