Friday, 20 January 2017

That isn't yellow! That's blue-orange!

LED lighting has become hugely popular. I can understand why. They consume little power, and come in all kinds of sizes and colours. LED bulbs can even replace "old fashioned" bulbs in any kind of lamp. After my country banned the sale of incandescent bulbs, LED replacements are sold everywhere.
Yellow LED Christmas tree lights

Most of them come in the colour "warm white". It is warm, that can't be denied, but it isn't white.  It is a combination of blue and yellow. The LED itself produces blue light. It is covered in a yellow fluorescent material, and the mix between the yellow and the blue wavelength is ideally seen as white by the human eye.

Humans, on the other hand, come with different colour vision. Some are colour blind. Others, like me, have a more sensitive colour vision. I'm especially sensitive when it comes to tones of yellow. Very few sources of artificial light can produce a true yellow colour, and that is especially true for LEDs. The yellow component of cheap warm white LED light lies on the orange side of yellow, so the mixed colour comes out as "orange-blue". I can see both the orange and the blue in it. "Yellow" decorative LEDs are even worse. To my eyes, they are orange-blue, similar to a street lamp. It is an interesting colour, but it is far from yellow!

I have great difficulties explaining this to my SO. To his eyes, white LEDs are white and yellow LEDs are yellow. There is no such thing as yellow-blue or orange-blue to him. I call street lights purplish orange. To his eyes, they are orangeish yellow. This comes from a passionate hobby photographer, who is far from colour blind!

The NPS building in Bodø in yellow orange street lightTo make matters worse, my phone camera can't capture yellow-blue, orange-purple or any of those mixed colours. On the picture of Christmas tree lights above, the light to the left is a blue-orange LED and the one to the right is a beautiful yellow incandescent bulb. My phone camera captures both of the colours as "yellow".

The photo of the building was taken in bright purple-orange light. It shows up as yellow in the photo. The phone's "eye" has a colour vision more similar to my SO's eyes than to mine. This could be part of the reason why he is a so much better photographer. (No, just joking, it has something to do with talent too)

The painting below gives a better idea of what street lights look to me. It shows both the purple and the orange, although in real life the purple also shines through the bright orange light from the bulbs. It is impossible to mix this colour in a digital painting, because the screen can onyl produce red, green, and blue wavelengths. It can't do purple-orange.

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