White vs. Green Phos

A much debated topic as of the last several years, emotions can and do run deep with this topic. To understand the argument we must understand how the human eye works.

The retinas of our eyes have 2 types of photoreceptors: Rods for Night and Cones for Day. We humans primarily use our Cone cells (color) when viewing through Night Vision devices. Of which there are 3 kinds of Cones: Red, Green and Blue sensitive. Cones also give you spatial acuity. The rod and cone cells are distributed evenly throughout the retina, except in a small central area called the fovea, where there are only cone cells. The fovea is the part used for detailed vision, like for reading. It takes about a thousand times more light to activate the color cone cells than it does the B/W rods, which is why detail, depth, etc. are much better when using both cones and rods, instead of just rods. Rods do not provide much detail

When using Green NV (GP) we use our Green Cone cells which make up only about 1/3 of our day vision.  Humans generally don’t use Rod cells with Green Phosphor night vision systems.

With White NV (WP)—White being the sum of all colors—we engage 100% of our day vision cones. So WP is engaging all of our day vision mechanisms (Cones) and even some of our night vision mechanisms (Rods), WP also has a strong Blue component in the 400 nanometer range, where we engage a measurable portion of our Rod cells.

With WP it would be akin to being able to use more of your brain processing power to think through and solve problems, you can certainly do it with GP, but you’ll probably do it faster with WP due to the physiology involved. We are getting more light data to our brain. This leads to reduced fatigue because we are not working as hard to gather the same amount of info. Contrast is higher and data feed is broader

“But Sam, the human eye can detect more shades of green than any other color in the visible spectrum”, Yeah I’ve heard that a time or two. Here is what you need to know about that, the dark adapted human eye is capable of detecting more shades of green than any other color, what happens when you power up a bright phosphor screen in front of your eye? Bingo, no longer dark adapted so that Voodoo science goes right out the window.

Colorblindness is generally a genetic mutation of one of or a combination of the Red, Green or Blue Cone photoreceptor cells in your eyes. True color blindness genes are carried on the X-chromosome, which is why it is spread from Grandfather to Grandson, very rarely is it expressed in women or any of the other 54 genders. If you are truly colorblind, then that can affect your choice a bit, but WP probably still comes out on top for the reasons I outlined above. If you can't see Green, then WP is even more clearly the choice. If you can't see Red and Blue, then maybe GP is the better choice for you.

All that said...it STILL comes down to personal preference for many people and nothing compares to trying both GP and WP in-person over an extended period of time to truly see which phosphor color one prefers. The physio/neurological basis for the detail, contrast and fatigue advantages of WP are true regardless—but remember this as well, some people are born with more of one type of photoreceptors than other folks and the same can be said about rods, as some people’s natural unaided NV is better than others, so genetics can come into play a little. Finally, individual tube specs and NV Generation are important variables (i.e.: EBI for contrast, Resolution and SNR for detail, Halo value for masking certain objects etc.) to consider, but need to be taken into account independently of phosphor choice for a truly useful comparison of WP vs GP.