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Visual comparison is the ultimate. You will find that it is so precise that you can have repeatable disagreements between different observers of when a match is achieved.
Decades ago, we had at Zenith a visual comparison unit using a fluorescent source (so the current did not require setting as it does with an incandescent source). One of the older engineers and I disagreed on how much blue was needed on the CRT to match the comparator, he requiring considerably more blue. I never found out the cause, but one possibility was natural browning of his eyes' lenses with age. Also, he had dark hair and brown eyes, an indication of likely greater deep violet / near-UV attenuation in his eyes (I am blond/blue). My experience with cataracts and my own lenses' aging is that they never got to the point of requiring more blue, even though after getting one operated on, I could see the difference in V/UV response to daylight.
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