Our light-sensitive cells can detect light in a small range of wavelengths. Light within this range stimulates our neural cells to create the perception of colors. Longer wavelengths are known as red and shorter ones as violet. See Figure 1.
White light consists of all the colors in the visible spectrum. When an object, illuminated by white light, reflects the red portion of the light (and at the same time, absorbs the other wavelengths), the object will appear red.
Sunglass tints serve as filters. They allow certain wavelengths to pass… while absorbing the other wavelengths to one degree or another. A red tint will primarily allow red light to pass. For this reason, the lenses look red when held up to a white light. A grey tint absorbs wavelengths across the visible spectrum. It doesn’t look black because it is not completely blocking all of the light, it’s simply reducing the amount of light of each wavelength.
In this way, red writing on a white paper will be difficult to see when looking through a red tint. In white light, the white background reflects all wavelengths of light, but only the red portion will pass through the tint. The red lettering will reflect only the red portion of the white light, and it will be transmitted by the red tint. To the observer, the paper will appear all red. The lettering will effectively disappear due to the filter – or at the very least, the lettering will be more difficult to see.
In contrast, a grey tint will allow the red lettering on white paper to remain visible because it is simply reducing the amount of light (affecting all wavelengths similarly) as it passes through the filter. In other words, it would be a darker version of looking at the paper with red lettering without using any tint.
To make tints work for fishing, ideally, the filter must make the background disappear (making the fish stand out) or the fish look black (or dark) in front of a non-black background. It’s a tall order. And if we choose the wrong tint, it can make fish even more difficult to see.
To choose a tint for fishing, we must know the colors of the fish and the colors of the background. In this way, we can use the differences in their colors to accentuate them. To use the example of the red lettering on white paper, if we used a tint that blocked red wavelengths only, the lettering would look dark and the paper would look greenish-blue or cyan (white light without red).
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