I was playing around with some red-cyan anaglyphs and my son pointed out that
the "red" portion of the screen wasn't perfectly blocked by the "red" lens.  Is
there a technological limitation here (see thread about "yellow" lens), or is
there just a more perfect rgb value I might be able to find?

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gregjohn wrote:
> I was playing around with some red-cyan anaglyphs and my son pointed out that
> the "red" portion of the screen wasn't perfectly blocked by the "red" lens.  Is
> there a technological limitation here (see thread about "yellow" lens), or is
> there just a more perfect rgb value I might be able to find?

Uh, no, the *cyan* lense is supposed to block red. The *red* lense is 
supposed to let it through. It shouldn't be blocking it at all.

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Invisible wrote:
> gregjohn wrote:
>> I was playing around with some red-cyan anaglyphs and my son pointed 
>> out that
>> the "red" portion of the screen wasn't perfectly blocked by the "red" 
>> lens.  Is
>> there a technological limitation here (see thread about "yellow" 
>> lens), or is
>> there just a more perfect rgb value I might be able to find?
> 
> Uh, no, the *cyan* lense is supposed to block red. The *red* lense is 
> supposed to let it through. It shouldn't be blocking it at all.

It should make it not visible at all which I think is what Greg meant.

Through the red lens, light coming from the cyan parts is filtered out, 
  therefore the cyan parts are visible in black. Light coming from the 
red parts and light coming from the white parts should in theory end up 
at exactly the same color, thus you can't distinguish the red parts when 
you look through the red lens.

Maybe the red used on the screen is a bit too dark, which makes the red 
areas appear as  slight shadows. Using light gray instead of white for 
the background might solve the issue...

-- 
Vincent

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>> Uh, no, the *cyan* lense is supposed to block red. The *red* lense is 
>> supposed to let it through. It shouldn't be blocking it at all.
> 
> It should make it not visible at all which I think is what Greg meant.
> 
> Through the red lens, light coming from the cyan parts is filtered out, 
>  therefore the cyan parts are visible in black. Light coming from the 
> red parts and light coming from the white parts should in theory end up 
> at exactly the same color, thus you can't distinguish the red parts when 
> you look through the red lens.

Or rather, with the red lense, black appears as black, red appears as 
red, and any other colour appears as black. (At least, ideally.)

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Invisible <voi### [at] devnull> wrote:
> Uh, no, the *cyan* lense is supposed to block red. The *red* lense is 
> supposed to let it through. It shouldn't be blocking it at all.

  The cyan lens blocks red light... making it look black. The red lens
blocks everything else other than red.

  Thus it depends on whether the *background* is black or white which lens
allows you to see the red lines. When looked through the red lens, a red
line against a white background will not be visible because everything
looks red. However, a red line against a black background will be visible
because the red line is the only thing which reflects light (and passes
through the lens).

-- 
                                                          - Warp

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"gregjohn" <pte### [at] yahoocom> wrote:
> I was playing around with some red-cyan anaglyphs and my son pointed out that
> the "red" portion of the screen wasn't perfectly blocked by the "red" lens.  Is
> there a technological limitation here (see thread about "yellow" lens), or is
> there just a more perfect rgb value I might be able to find?

I remember old 3-D comic books and such having the same problem. I think the
main limitation is the rather broad-spectrum 'red' color that is used in those
inexpensive cellophane glasses. They let pass too many light frequencies
'around' the red (or block too few??) I suppose an *ideal* red filter would need
to be almost monochromatic--and matched exactly to the printed color of the
anaglyph (or the projected color of a film/transparency.)

Ken

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Kenneth wrote:
> matched exactly to the printed color 

You'd need a very saturated printed color, too, or your ambient light would 
affect the results too much. At which point I'm not sure you wouldn't be 
messing up the cyan side of it.

On a slightly different topic, I saw one of the Sony 3D TVs today. 
Interesting, but not ready for prime time, IMO.

-- 
Darren New, San Diego CA, USA (PST)
   Forget "focus follows mouse." When do
   I get "focus follows gaze"?

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Update:

For the same image, on SCREEN, the RED red lens doesn't do what it's supposed to
do-- shows ghost images of stuff not appropriately blocked.

When PRINTED, the CYAN lens doesn't do what it's supposed to do.

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gregjohn wrote:
> Update:
> 
> For the same image, on SCREEN, the RED red lens doesn't do what it's supposed to
> do-- shows ghost images of stuff not appropriately blocked.
> 
> When PRINTED, the CYAN lens doesn't do what it's supposed to do.

Sounds to me like either the glasses or the screen/printer are not 
perfectly calibrated. There probably isn't a lot you can do about that...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Darren New wrote:

> On a slightly different topic, I saw one of the Sony 3D TVs today. 
> Interesting, but not ready for prime time, IMO.

I don't know what technology they use, but there's some "3D TVs" at my 
local shopping center. As you walk past them, they have a vaguely 
hologram-like quality to them. But it doesn't look particularly 3D; more 
like as you walk past, the image changes in discrete steps. Novel, but 
not very realistic.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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