It is a reasonable question, because a darker lens does reduce the amount of light passing through it. Many owners like the look of smoked or blacked-out gauge lenses, but naturally wonder whether that styling change will make the gauges harder to see.
In actual use, Porsche 914 gauges generally remain easy to read in daylight even with darkened lenses. The original VDO dial design already has strong white markings and good contrast. A darker lens may slightly reduce overall light transmission, but it can also reduce reflections and give the gauge face a deeper, higher-contrast appearance. The result is usually more of a styling change with some optical tradeoffs rather than a major loss of readability.
