Color, Colortemp, CRI, TM30 and depth perception ?

[QDubs]

I've perused this forum for years and used it for purchase advice often (thank you everyone!). First time post.

I'm trying to better understand the effect of light quality on depth perception (and perhaps comfort and eye strain). For instance, for lighting crossings in a road junction or lighting a bikeway - what qualities are important for people to be able to see obstructions clearly?

Seemingly Cool/Blueish is worst and Warm/Redish the best? But a warm 2200k with low R9 or R10 might not be so good?

Some bikeways in The Netherlands are lit w/ a slight greenish tint and this is surprisingly comfortable on eyes and seemingly provides good depth perception but being close to blue this shouldn't be?

Thanks,

 

[JustAnOldFashionedLEDGuy]

Cool light is superior for reaction speed, contrast perception, and object detection at lower light levels. It creates higher glare perception if you look right at it. Neutral (around 4K) can provide better contrast in natural settings at lower light levels and is generally a good trade off between glare and visual acuity. There can be an advantage is absolute resolution at lower CCT, but this is normally balanced against poor depth of focus, and is not required for object detection/safety in a road/cycling environment.

Green is not that close to blue really. It is in the middle. That light is designed to have reduced circadian rhythm impact, but is arguably inferior for best objective detection / safety. Being absent blue you may find it easy on the eyes, but blue is generating a glare response, not hurting your eyes at these light levels. Alert is a good thing.

 

[Owen]

Cool light is superior for reaction speed, contrast perception, and object detection at lower light levels.

The relationship between colors is fixed, and the ability to differentiate between objects is based on contrast between them-which typically suffers with cool white LEDs. It's such a factor that there are now low contrast tests for medical conditions resulting in degenerated vision, as our contrast-based visual acuity actually "hides" that damage by allowing people to pass normal vision tests in spite of having other issues with their eyesight.

 

[JustAnOldFashionedLEDGuy]

The relationship between colors is fixed, and the ability to differentiate between objects is based on contrast between them-which typically suffers with cool white LEDs. It's such a factor that there are now low contrast tests for medical conditions resulting in degenerated vision, as our contrast-based visual acuity actually "hides" that damage by allowing people to pass normal vision tests in spite of having other issues with their eyesight.

The op asked specifically about object detection in a roadway crossing and/or bike path. To that end your post is wrong. Research has shown in the past that at reduced light levels (mesopic and into photopic as you will get peripherally) that bluer light will result in faster reaction times and better contrast for object detection.

Even if the lighting levels are technically photopic you aren't guaranteed reflection levels are such with the light levels of roads and paths and people and objects on them are, hence the advantage of blue skewed light.

On highways where you are technically looking out seconds ahead, there is little evidence of advantage of bluer skewed light, however, for low speed roads (and bikeways) there is research indicating that light with a higher scotopic/photopic ratio is superior, especially for detecting the entry of objects from outside the primary lighting area that are dimmer.

Contrast does not suffer with cool LEDs. It is object / spectrum richness dependent, though with typical low CRI of outdoor LEDs / streetlighting, neutral (around 4000K), seems to provide highest typical contrast with purely photopic vision.

I will put a caveat that if the light sources are designed such that they are creating glare, that that will impede object detection and this can be made worse by cooler sources.

 

[QDubs]

Thank you. One specific example is a crossing where the old light heads were changed out to LED a couple of years ago. They appear very cool/blue but I've not way currently to measure them (I'd love to get a C-800 color meter one day). There are a couple of very poorly placed 3' high posts for crossing buttons that people must navigate. They are not a problem when approaching from the bikeway as people are slowing down to stop but when crossing towards them (which must be done a somewhat high speed to avoid being hit by cars due to a too-short light cycle) many people have complained about the new lighting making them more difficult to see or judge exactly where they are.

I'll try to get a photo tonight of this one.