Definition: revealing insight and understanding; discriminating; capable of seeing, knowing, and judging; sharp-sighted; shrewd; astute <discerning motives>
Quote: The unaided human eye, under the best possible viewing conditions, comparing large areas of color, in good illumination, using both eyes, can distinguish 10,000,000 different colored surfaces. — 1986 Guinness Book of World Records
Comment: It doesn’t matter what some so-called expert says about it, you’re going to decide for yourself anyway. You may open your ear a little bit wider if you happen to believe the source has good credentials, but even then you are the one sifting the information through your filters.