P3D Re: "Too much depth" Part 2 of 3

[Gabriel Jacob <jacob@xxxxxxxxxxxxxx>]

I wrote,
>>I'm not following this. The parallax you refer to is a
>>retinal disparity. At close distances it's still a
>>retinal disparity. Therefore distance doesn't come
>>into play. Granted at farther distances the parallax
>>is probably more important but the "key" word is that
>>they're BOTH retinal disparities. This retinal
>>disparity simply is the difference in perspective
>>regardless if the disparity is within the object or
>>the edges of the object (as in parallax).

Chris replies,
>So you would say that the brain processes all retinal
>disparities through the same mechanism?

Never said that, but then again what do you specifically
mean by "mechanism?" There seems to be some confusion
on this matter. If your trying to say that the 
"stereostereopsis" process differs, depending on the
distance, please say so! :-) So far you have said in
close distances we have vergence cues and these (as
I mentioned in my last post) are monocular cues.
 
Chris,
>But there is more than one kind of stereopsis. The
>distant case I described is known as "quantitative" or
>"fine" stereopsis, and the close-up case is "qualitative"
>or "coarse" stereopsis. It's a different process even
>if the results are broadly similar. And can arise from
>different cues.

That's interesting but why is the processing different?
What exact mechanism is at play for disparity to be
processed differently at different distances (assuming
that is what you mean, best I can gather). 

Gabriel
>>That's interesting but I haven't seen any examples or
>>proof of this yet (that it is a different process).
>>Wouldn't it still be retinal disparity at play here?

Chris,
>It's always retinal disparity in stereopsis. The original
>1971 reference for this is in the post just previous to this
>one, by Bishop & Henry.

Yes, I know. This was a rhetorical question. :-)

Chris,
>But would the brain be able to make use of static, out-of-focus
>information? Not anywhere near as well as it would be able to
>use dynamic out-of-focus input, I think.

I'm not sure.

Chris
>> More on that below, but consider still photography - would a
>>"natural" snapshot of moving two pencils together at a small
>>distance be useful, or make a "good" image?

Gabriel
>Yes, I think so.

Chris,
>What for? A snapshot of what I see would probably be the
>in-focus tip of one pencil and then a big diplopic mess.
>That's natural but a pretty poor image, IMHO.

I don't know about that.

Gabriel