Increasing the brightness of an OLED pixel

[jebez]

Increasing the brightness of an OLED pixel (display in general), the 3 sub-pixels are added or multiplied?
Is it R+x, G+x & B+x or R*x, G*x & B*x ? (Red Green Blue).

[Posted edited by a Mentor]

 

[Andy Resnick]

Increasing the brightness of an OLED pixel (display in general), the 3 sub-pixels are added or multiplied?
Is it R+x, G+x & B+x or R*x, G*x & B*x ? (Red Green Blue).

Neither- you can't arbitrarily increase the output brightness to whatever level you would like.

 

[jebez]

Huh? The brightness of my ViewSonic VP-16 OLED monitor can be increased from 0 to 100%, by my PC running Arch Linux KDE...

 

[Andy Resnick]

Huh? The brightness of my ViewSonic VP-16 OLED monitor can be increased from 0 to 100%, by my PC running Arch Linux KDE...

Maybe I misunderstood your question- I don't think you can boost the output of your ViewSonic VP-16 OLED monitor beyond 400 nits (ViewSonic 15.6" VP16-OLED Thin Portable Monitor), no matter how hard you drive the OLED display.

Are you asking if the 0-100% brightness scale is a linear scale?

 

[jebez]

omg my 1st post isn't clear?

 

[berkeman]

omg my 1st post isn't clear?

Not really.

Are you asking if the 0-100% brightness scale is a linear scale?

Or are you asking if you can go beyond 100% somehow?

 

[Dale]

Increasing the brightness of an OLED pixel (display in general), the 3 sub-pixels are added or multiplied?
Is it R+x, G+x & B+x or R*x, G*x & B*x ? (Red Green Blue).

They are added. If they were multiplied then if any one were zero then the brightness would be zero, even if the others were 100%

 

[berkeman]

the 3 sub-pixels are added or multiplied?
Is it R+x, G+x & B+x or R*x, G*x & B*x ? (Red Green Blue).

They are added. If they were multiplied then if any one were zero then the brightness would be zero, even if the others were 100%

That's part of the problem with the wording of the OP. He says "the brightness of the pixels is multiplied" but the (partial) expression he writes has each pixel's brightness multiplied by some scale factor x, not multiplying the brightness of the other pixels.

 

[jebez]

I can't edit my 1st post, clearer:

Increasing the brightness of an emissive display, how a pixel?​

Emissive display: OLED, CRT etc, not LCD.
Are the values of the 3 sub-pixels added or multiplied by a same value, or other?
Is it R+x, G+x & B+x or nothing if a sub-pixel is off, R*x, G*x & B*x or other? (Red Green Blue).

 

[pbuk]

Are the values of the 3 sub-pixels added or multiplied by a same value, or other?

Other.

Exactly what 'other' is (or if there is even a meaningful answer to your question) depends on what you mean by "values" and "brightness" and at what stage of the image generation process you are "increasing the brightness" (application software -> operating system -> device driver -> graphics card firmware -> graphics hardware -> display firmware -> display controller hardware -> display pixel).

omg my 1st post isn't clear?

No, can you now see why?

And drop the attitude.

 

[jebez]

Value of a sub-pixel: on 8 bits, 1 octet https://en.wikipedia.org/wiki/Color_depth#True_color_(24-bit) , 2^8=256 values possibles, 256^3=16 777 216 colors possible (3 sub-pixels).
Brightness: Arch Linux KDE, panel, Screen Brightness from 0 to 100%.

Aggravating_Bear9268 in the reddit link understood, wow! He answered multiplied by a same factor.

 

[pbuk]

Value of a sub-pixel: its luminance, intensity.

Really? Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction (https://en.wikipedia.org/wiki/Luminance). It is not measured on a scale of 0-255.

Brightness: Arch Linux KDE, panel, Screen Brightness from 0 to 100%.

I don't know how KDE's settings work but I would imagine that the 0-100 scale is calibrated to provide some level of perceptual consistency i.e. the amount of perceptual change between 10% and 20% is similar to that between 80% and 90%. This is unlikely to result in a linear scale. There may also be gamma correction involved.

Aggravating_Bear9268 in the reddit link understood, wow! He answered multiplied by a same factor.

I am glad that you are satisfied by that answer.

Can I suggest an experiment to see if it is correct? The background of the square below is white: it has the RGB colour value of 0xFFFFFF i.e. each sub-pixel has a value of 255. Now turn the brightness up. What value do you think the sub-pixels have now? Have they been multiplied by some factor?

 

[jebez]

Well e.g. a red sub-pixel has the value 142, at brightness 0% it emits x watt, I increase the brightness to 24%: it emits 24*x or 24*a+x watt? a is constant.

 

[Dale]

That is much clearer. Please ignore my previous answer. I completely misunderstood your question.

 

[pbuk]

Well e.g. a red sub-pixel has the value 142, at brightness 0% it emits x watts, I increase the brightness to 24%: it emits 24*x or 24*a+x watts? a is constant.

Neither. The relationship between RGB values and output power is much more complicated than that. There are also non-linear relationships between output power and luminance, and between luminance and perceived brightness to take into account, and also the fact that these relationships are different for red, green and blue pixels.

I can't find a short summary of this at the moment: you can get a reasonable overview by asking your favourite AI "how does an rgb setting convert to pixel brightness" or some such.

But if you are looking for a simple answer rather than an introduction to a large and complicated subject then I am afraid there isn't one.

 

[jebez]

I care not if sub-pixel value & output power is linear or not, I'm interested by the relationship between the 3 sub-pixels, back to my 1st post:

Static image on a OLED display at brightness 0%, a pixel has 3 sub-pixels emitting r, g & b watt.
I increase the brightness: now they emit rx, gx & bx or r+x, g+x & b+x (or nothing if a sub-pixel is off) watt? Or other?

 

[berkeman]

brightness 0%, a pixel has 3 sub-pixels emitting r, g & b watt.
I increase the brightness: now they emit rx, gx & bx

if r=g=b=0, then xr=xg=xb=0.

 

[pbuk]

I'm interested by the relationship between the 3 sub-pixels

Because the eye and brain detect red, green and blue light in different ways, to achieve an increase in brightness without changing the perceived colour the 3 sub-pixels are increased by different amounts.

For an introduction to the complexity of this see for example https://en.wikipedia.org/wiki/Gamma...perform_display_gamma_correction_in_computing

 

[AlexB23]

Increasing the brightness of an OLED pixel (display in general), the 3 sub-pixels are added or multiplied?
Is it R+x, G+x & B+x or R*x, G*x & B*x ? (Red Green Blue).

[Posted edited by a Mentor]

Do you have a light meter? You can measure the flux at a fixed distance for both red, green , blue, and white full screen images at the screen's minimum, 50%, and maximum brightness. Then, you can use an online color mixer as well and measure the brightness. When in doubt, quantitatively figure it out.

 

[jebez]

I think it's like audio on a PC:
sub-pixel value (0 to 255) goes to a DAC (digital to analog converter) then amplified, multiplied (brightness) by a transistor.

I googled a lot without finding, confirmation...