Glow in the dark keys

[Binky]

If you look, they have the backlight cranked up -a lot- to get enough light out of the key shapes to be usable. Inverse the scheme and the amount of back lighting needed, and power use for it, would drop by 80-90%.

How can you tell all that from a single photo?

 

[moxie]

Grench has access to photo analysis software from Blade Runner, so he can twist the keyboard around, find the computer it is attached to and read its configuration files.

 

[Grench]

If you look, they have the backlight cranked up -a lot- to get enough light out of the key shapes to be usable. Inverse the scheme and the amount of back lighting needed, and power use for it, would drop by 80-90%.

 
How can you tell all that from a single photo?

Grench has access to photo analysis software from Blade Runner, so he can twist the keyboard around, find the computer it is attached to and read its configuration files.

It's simple logic actually.  It is not even specific device dependent. Let me walk you through it.


In order to transmit light, the core of the LED back lit keypad has to be translucent - regardless of whether it is going to be white letters on black background or black letters on white background.


Paint used to apply the black coating over the translucent material is black on both sides.


Black paint appears black because it absorbs all light in the visible spectrum.


Any light being piped up from the keyboard backlight LEDs that strikes the black paint is wasted. At that point all it can do is be converted to some trivial amount of heat at the paint level.


The only usable light being emitted from the key tops is contained within the portion that is not covered in black paint.


With black letters on a translucent background, 80-90% of the key top is left white - and can transmit the light hitting it from beneath.


With white letters on a black painted background, 10-20% of the key top is left white - and can transmit the light hitting it from beneath.


To achieve similar key-level brightness then, the back light of a light key with dark letters keyboard would require far lower brightness levels to achieve similar results. It is simply more efficient because there is not as much light wasted on being shone on black paint.


Lower brightness required at the key tops results in lower brightness at the LED which means less energy required.

 

[_wb_]

Instead of black paint, I would use a layer of reflective paint at the bottom (led side) and a layer of black at the top. That would reflect back most of the wasted light until it hits an exit, at least if you also have a reflective layer at the bottom of the light spreading keymat.

 

[Grench]

Instead of black paint, I would use a layer of reflective paint at the bottom (led side) and a layer of black at the top. That would reflect back most of the wasted light until it hits an exit, at least if you also have a reflective layer at the bottom of the light spreading keymat.

Good luck getting a chunk of thin rubber to line up perfectly and mask off to letter outlines exactly through the application, drying, then 2nd application, drying of two coats of paint.  The paint applications at that level of precision could quickly cost more than the price of the keymat itself.  The energy wasted by the LEDs shining on black would likely be much cheaper.

 

[_wb_]

Instead of black paint, I would use a layer of reflective paint at the bottom (led side) and a layer of black at the top. That would reflect back most of the wasted light until it hits an exit, at least if you also have a reflective layer at the bottom of the light spreading keymat.

Good luck getting a chunk of thin rubber to line up perfectly and mask off to letter outlines exactly through the application, drying, then 2nd application, drying of two coats of paint.  The paint applications at that level of precision could quickly cost more than the price of the keymat itself.  The energy wasted by the LEDs shining on black would likely be much cheaper.

Why would it require more precision to apply two coats of paint instead of one?

 

[Klumpen]

Instead of black paint, I would use a layer of reflective paint at the bottom (led side) and a layer of black at the top. That would reflect back most of the wasted light until it hits an exit, at least if you also have a reflective layer at the bottom of the light spreading keymat.

Good luck getting a chunk of thin rubber to line up perfectly and mask off to letter outlines exactly through the application, drying, then 2nd application, drying of two coats of paint.  The paint applications at that level of precision could quickly cost more than the price of the keymat itself.  The energy wasted by the LEDs shining on black would likely be much cheaper.

Why would it require more precision to apply two coats of paint instead of one?

Because the letters need to stay unpainted from both sides to let the light shine through.

I got his point and it's true.

I'd vote for white on black though in spite of a minimal higher energy consumption, because it causes less eye strain for me

and I only need it for short periods of time and not very often, but when I need it, I want it to be available in a nice way.

 

[Grench]

Instead of black paint, I would use a layer of reflective paint at the bottom (led side) and a layer of black at the top. That would reflect back most of the wasted light until it hits an exit, at least if you also have a reflective layer at the bottom of the light spreading keymat.

Good luck getting a chunk of thin rubber to line up perfectly and mask off to letter outlines exactly through the application, drying, then 2nd application, drying of two coats of paint.  The paint applications at that level of precision could quickly cost more than the price of the keymat itself.  The energy wasted by the LEDs shining on black would likely be much cheaper.

Why would it require more precision to apply two coats of paint instead of one?

Take a piece of paper and set it on the desk in front of you.  Close your eyes.  Feel the edges of the paper to orient yourself.  Draw a line down the middle of the paper (eyes still closed).  Take a look.  Probably looks like a nice line down the middle of a page.

Close your eyes again and flip the paper over twice.  Feel the edges of the paper to orient yourself.  Draw a 2nd line down the middle of the paper (eyes still closed).  How close did you get the two lines?

In the above example, one line on the page looks fine because there isn't anything to say it's off.  If you're going to make 2 lines overlap exactly, then you're going to need to be extraordinarily accurate with both.

Two lines shows the error in drawing each line.

 

[Grench]

I'd vote for white on black though in spite of a minimal higher energy consumption, because it causes less eye strain for me

and I only need it for short periods of time and not very often, but when I need it, I want it to be available in a nice way.

Do you have access to a good quality laser printer?

Print a page of text in black letters on white paper.

Print a 2nd page of text with the page colors inverted so that it yields white letters on black paper.

Which is easier to read?

Or even change your forum settings so that they're white letters on black background.  (Not 100% sure it's possible.)

Notice that the default is black letters on a white field.  That's because it is easier for most people to read.  Your eyes may be different.

 

[Klumpen]

I'd vote for white on black though in spite of a minimal higher energy consumption, because it causes less eye strain for me

and I only need it for short periods of time and not very often, but when I need it, I want it to be available in a nice way.

Do you have access to a good quality laser printer?

Print a page of text in black letters on white paper.

Print a 2nd page of text with the page colors inverted so that it yields white letters on black paper.

Which is easier to read?

Or even change your forum settings so that they're white letters on black background.  (Not 100% sure it's possible.)

Notice that the default is black letters on a white field.  That's because it is easier for most people to read.  Your eyes may be different.

Do the same experiment laying the paper on an old overhead projector (or any other backlit surface) in a dark room

and you got the right comparison, yours is flawed.

Notice that the default is black letters on a white field.  That's because it is easier for most people to read.  Your eyes may be different.

That's because paper naturally does not come in black.

 

[Grench]

I'd vote for white on black though in spite of a minimal higher energy consumption, because it causes less eye strain for me

and I only need it for short periods of time and not very often, but when I need it, I want it to be available in a nice way.

Do you have access to a good quality laser printer?

Print a page of text in black letters on white paper.

Print a 2nd page of text with the page colors inverted so that it yields white letters on black paper.

Which is easier to read?

Or even change your forum settings so that they're white letters on black background.  (Not 100% sure it's possible.)

Notice that the default is black letters on a white field.  That's because it is easier for most people to read.  Your eyes may be different.

Do the same experiment laying the paper on an old overhead projector (or any other backlit surface) in a dark room

and you got the right comparison, yours is flawed.

Keep the dark room.  Start turning down the power to the bulb on the theoretical old overhead projector.  Which one is still legible while using the least amount of light from the source bulb?

 

[moxie]

Notice that the default is black letters on a white field.  That's because it is easier for most people to read.

Actually, that is not true. Or rather, yes, it is true of a laser printer printout, for much the same reasons that you give about the two layers of paint above, but it isn't generally true, and certainly not for text on a screen (why you'd bring that in, I don't know, since it is a fundamentally different thing than reading on keycaps, but there you go...). For text on screen, the most readable combination is very close to the good old amber terminals - Amber text on black background. The reason we do get black-on-white on most websites is a carryover from print design (where black-on-white is easier), but it is not the most readable, nor the most restful for the eyes.

The reason for this is light pollution - Big fields of intense light is tiring for the eyes. We get non-meaningful activation of a lot of retina cells at quite strong levels, which in the end tires our eyes. Keeping the high-intensity areas small and meaning-carrying will allow your eyes to last a lot longer.

 

[Klumpen]

If there would be a way to make these boards amber on black, I would switch to that immediately

and actually my old boards all looked a bit like that.

All those bright backlit fields (because of my monitor, where I reduced the brightness already)

are tiring indeed and since it is not paper (which is reflecting light rather than emitting it...),

I do not see a reason for black on white at all.

 

[Binky]

Also, don't forget that although black print on transparent keys may result in greater light transmission, there is a greater area being illuminated.

The relative brightnesses will be exactly the same either way round.

If you had high-enough precision printing that the black areas were reflective on the back, the difference in brightnesses would be far higher than with black-on-transparent - resulting in lower energy consumption and higher efficiency.

 

[slaeshjag]

As someone having owned cellphones with both transparent background, and transparent on black, I prefer the latter. More readable, and looks a lot better.

If the chinese can do it on a $40 cellphone, I'd hope a reasonably good effort at it can be made for a successor.

 

[_wb_]

I get the point about the precision, but can't it mostly be solved by noting that the reflective coat is optional (it's just an efficiency optimization), so you could use a paint mask with bigger holes (i.e. bolder lettering) to compensate for inaccuracies. Only the black paint has to be correct.

Anyway, I agree with most others that black lettering on translucent backlit keys looks fugly, even though Grench' point about efficiency is probably valid.