Tuesday, 25 August 2015

"Color for the Color Blind" - A quick review of EnChroma Sunglasses

I'm severely Red-Green Colour Blind (technically, I have Deuteranomaly https://en.wikipedia.org/wiki/Color_blindness#Types, a genetically transmitted condistion). 

I’ve just acquired a pair of EnChroma Cx Explorer sunglasses, which are designed to boost colour perception for many people who suffer from colour blindness. (See http://enchroma.com/

The theory is that for people with normal vision, the Red receptors in the eye respond strongly to red, but only moderately to red-green colours, while the Green receptors respond strongly to green, but only moderately to red-green colours. For people with Red-Green colour blindness (which is my problem), the red and green receptors in the eye overlap in their colour reception, and both respond strongly to similar wavelengths in the red-green range, so they don't differentiate between red and green as well as a normal eye.

The EnChroma lenses effectively transmit red and green, but largely block the intermediate red-green colours, so the red receptors will be triggered strongly by red but not by red-green (which are blocked by the lenses), while the green receptors will be triggered by green but not red-green. 

Where these glasses differ from other products that I have seen advertised before is that these use narrow band-pass "notch" filters to cut out a very tightly defined band of red-green, whereas the more common type use pigmented dye filters, which filter out a wider and less clearly defined band of colours. 

(The EnChroma lenses also have a "notch" for blue-green, which could be beneficial for some forms of colour-blindness, but is probably not so important for me - although maybe it helps with the overall effect as well?) 

My pair arrived yesterday.

So - do they work? In a word:


They're quite dark (just 14% overall light transmission), so they're intended for full daylight use, not really suited for indoor use. If you're wondering - 14% transmission is pretty typical for a sunglass lens designed for full sunlight. E.g. Oakley provide a range of tints from 9% to 11% for "Extremely bright light", while 13% to 22% are rated for "Medium to bright light".

EnChroma offers three lens shades: 14% for "strong daylight", 25% for "medium-to-low light outdoor conditions" and brightly-lit indoor use, and 65% for general indoor / computer use. The 14% has the strongest colour-correcting effect, which is why I chose it.

In muted light this morning (7:30 am, a bit of light cloud / mist), the effect outdoors was obvious - a lot more contrast and definition between various shades of green and red in the garden.

But as the sun broke through - WOW!

Colours became quite eye-popping - our dry winter lawn became a vivid green, pastel flowers that always faded into the background suddenly stood out ...

The most dramatic difference was driving in to work - so, green traffic lights are actually green? Who knew?! J

(Green traffic lights have always looked almost white to my eye, with only the slightest hint of colour, but now they are bright green. Also, for the first time ever, red traffic lights are brighter than amber traffic lights, whereas the amber has always been quite a bit brighter than the red to my eye.)

Some unexpected effects - they can give a strong green cast to some (but not all) digital displays - my Android tablet is now green when it should be white, but my phone looks normal. There's an LED display board outside the Convention Centre which is now green, but as I sit at my computer typing this, the white background is just white. I guess it depends on the exact colour spectrum of the pixels.

I'll by trying to catch a spectrum tonight using my Public Lab Spectrometer http://publiclab.org/wiki/spectrometer - I'm expecting to pick up a couple of strong "notches" in the white light spectrum. I'll post here when I've captured a useful spectrum.

(For the sceptics: There is some “real science” behind these glasses, which differentiates them from other tinted sunglasses which have been promoted as "cures" for colour blindness – e.g. see: