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Frequently Asked Questions

What is Bicovi?
Don't Red + Green make Yellow?
Pronunciation of 'Bicovi'.
Why are the colours pale?
Colour names.

What is Bicovi?
A normal person has two eyes.  However, every colour theory and medical investigation into colour perception has been described as if there were only one eye involved.  This 'Binocular Colour Vision' website presents a colour theory wherein there are no primary or secondary colours in the conventional sense. 
    Colours can be mixed physically (as with paints) or optically (as in the dots on a television screen).  Either of these works for the one-eye model.  What happens when the eyes see different colours?  Normally the colours would be too intense and no mixing of the colours would occur.  The perceived colour might switch from one to the other but only one colour will be seen at a time.  However, if the colours are pale enough, colour fusion can result.  All colours can then be visually mixed  from adjacent colours on the colour wheel.
    When you mix red and yellow paints, you get orange. But you cannot mix any two paints to get a bright red or an acceptable yellow.  Red, yellow and blue are called paint primaries because they cannot be mixed from other colours.
    Similarly, if you present a pale red to one eye and yellow to the other, colour fusion can occur to give orange.  However, now you can use violet and orange to create red.  This works for any combination of colour pairs around the colour circle.  Thus all the colours are of equal importance.
    Finally, Bicovi colour mixing shares aspects of both subtractive and additive colour mixing.  The colours mix to give a subtractive result but the result is brighter than expected as if additively mixed.

Don't Red and Green make Yellow?
There are reports in the literature that dichoptic colour fusion of red and green produce yellow.  This is consistent with additive colour mixing.  This can be an initial perception especially with the Geometric and Helix figures.   However, systematic investigation of these figures will give a more consistent result if subtractive colour mixing is accepted.  This means that red+green=grey and orange+green=yellow.
As outlined in the Viewing Methods, care must be taken that the eyes are accommodated and that the eyes are dominance balanced.   The investigator must take care that the initial colours chosen are balanced.

Internet Link indicating that red and green produce yellow.
Research Paper (PDF Document):- "Multi-coloured stereograms unveil two binocular colour mechanisms in human vision." Casper J. Erkelens, Raymond van Ee; Vision Research 42 (2002) 1103–1112.

Pronunciation of 'Bicovi':- "bi-coe-vee".
Because the word comes from 'Binocular Colour Vision' you would expect it to be pronounced "bye-ku-vi" with a very short "i" at the end.  This is difficult say so "bye-ku-vee" would be the logical extension.
    However English drifts towards the easiest pronunciation of the word itself regardless of its origin.  Therefore "bi-coe-vee' (with a short "i") is probably the best choice.

Why are the colours pale?
This is to minimize 'retinal rivalry'.  If there is too large a difference between the images presented to each eye, as in the following figure, retinal rivalry will result.   The brain will see only one of the images (or a fluctuating combination of parts of each) rather than a fused image.

Review the Viewing Methods to learn how to fuse the two images

Retinal Conflict

Colour names.
    As noted in the previous question, the colours are pale.  Pale Red is usually called Pink.  However people would also say "Red plus Yellow make Orange".  To be consistent across conventions, I am calling the colours by their base names.
    Black and White occupy a curious middle ground in that they are "colour names" but are not actually coloured.  They are best thought of as colour modifiers or as a subset of colours as in "darker" or "lighter".

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