Kayak Lighting, Part 1 – Brightness
I thought so too at first. Then I actually started using really bright lights and immediately had some issues with it. So I looked into the question a bit deeper.
This post is going to drop a little science on you, but don't worry, I won't nerd out too much. Actually I couldn't even if I wanted to because I'm not a biologist or physician. But having a layman's understanding about how eyes actually work will help us make better choices for yak lighting.
How Eyes Work in the DarknessHuman eyes work in a remarkable range of light conditions, from ultra-bright sunlight to near complete darkness. Three parts of the eye work together to enable such versatility.
If you paid any attention in biology class, you already know the pupil acts as a light valve, expanding and contracting to let in more or less light. It does this very well with no conscious thought on our part. But that's only one piece of the puzzle.
The eyes contain two types of cells involved in seeing light: rods and cones. Rod cells detect only black and white and have poor resolution, but are very sensitive even in low light. Conversely, cones detect fine detail and color but require bright light to work. For our purposes in this article we are mostly interested in rods since they are the primary cells employed in night vision.
Rods and cones contain chemicals called photopigments that, when exposed to light, create the electrical impulses that our brains interpret as eyesight. Intense light causes the rods' photopigments to decompose, reducing sensitivity to dim light. Darkness causes the rod photopigments to regenerate. When you walk inside after being out in the bright sunlight, you're often temporarily blinded for many minutes until your pupils adjust to the relative darkness. That's the rod photopigments "recharging".
Eyes are much faster at adjusting to bright light than to darkness. In fact, rods are downright slow in adjusting. Cones adjust to bright light in about 5-7 minutes, but rods need a full 45 minutes or more of absolute darkness to reach just 80% adaptation to the dark. Completely adapting to total darkness can take many hours.
Blowing a Rod
All of this is why the brightness of a light is a two-edged sword for night fishing on a kayak. Obviously the brighter the light, the better the illumination and visibility you get. However, as you now know bright light will kill your natural night vision and the night vision of anybody who looks at it. And especially into it. And it will kill it for a good long time. Once you've done that, you're dependent on the artificial light, and good luck seeing anything beyond its range.
Positioning and aiming of your light so that it doesn't shine (or reflect) directly into your eyes helps. But you don't want others to be night-blinded either. Even if you don't give a damn about them, they could be driving the power boat that is headed your way.
You want enough light to safely illuminate what you're doing and/or increase your visibility to others, but not so much that you're destroying your or other people's night vision.
Therefore, the best kayaking light is not necessarily the brightest. It's the one that has (or can be adjusted to have) just enough brightness to achieve it's purpose, and no more. If you do get a really bright light, make sure it lets you adjust the brightness!
Red Light District
Airplane pilots will often wear red-tinted glasses for a half hour or so before flying in low light. They do this to maintain their night vision. The reason is that rod cells don’t pick up the color red (remember, black and white only), so they don't desensitize when the light they're seeing is filtered through red glasses. While other colored glasses would work to varying degrees, red is the most effective since it has the longest wavelength of all visible light and is the most invisible to rod cells.
The principle behind this trick is very helpful to us kayak fishermen too! If you have a red light mode on your flashlight, you can use it at night and it won't kill your night vision. It will attract fewer insects too! Lots of higher-end flashlights and headlamps have this feature and I recommend getting one that does.
Some other tips that are useful: First, wear good polarized sunglasses. Enough exposure to bright sunlight will permanently damage your night vision. Don't look directly into lights. And before going into a dark area, close your eyes for a few minutes (if you can do so safely) to give your eyes a head start on adapting.