But was an extra photopigment all that was needed to evolve trichromatic vision? 但是是否另一種感光色素必須完全進化成三色視覺？
In this view, trichromatic color vision can be considered a hobby of the preexisting spatial vision system. 或許也沒有這個必要，如果從這角度來看，我們可以把三色視覺看成既有空間視覺系統的次要活動。
A certification of colour vision shall be valid for a maximum period of six years. 色覺視力證書的最長有效期應為六年。
Our experiments provided evidence that birds use all four cones in their color vision. 我們的實驗證明，鳥類的色覺使用了所有四種錐細胞。
