Question about sunlight and monitorlight

I've a Question about light and colors for scientists ?

Lets assume we have 3 lightsources with freq1 < freq2 < freq3
And an observer.

Now I have the following question ?

Is it possible to create a continue spectrum of light between freq1 and freq3 just by adjusting the amplitude of the lightsource ?


The reason why I ask is the following. A monitor CRT (at least) has for so far I know Red green and blue pixels but no yellow and as we all know by changing the intensity of the pixels one can see all colors.

My question is quite blunt is this an optical illusion ? Or is really the entire spectrum of light emittable by a monitor.

I other words do we only see discrete light and make our brains up for the frequencys or are they really there. For instance If I see yellow thinks my brain it's yellow or is yellow frequency really there (the monochromatic yellow) ?

One way to test this is to funnel the light of the monitor to a prism , but I haven't one.

Mathematical I think it impossible to just by changing amplitude changing the frequency.
like
A*sin(Freq1) +B*sin(Freq2) = C*sin(Freq3)

Freq3 unequal Freq1
and Freq3 unequal Freq2

Another reason why I think that's impossible , because however you mix tree tones together and you never get a full octave of tones right ?

So if true ... the colors coming from our monitors are an illusion created in our brains or eyes. (discrete states translated into a continuum) and differs quite a lot from our sunlight.

Greetings.

a reply to: frenchfries

Is it possible to create a continue spectrum of light between freq1 and freq3 just by adjusting the amplitude of the lightsource ?

If the srcs are RGB and corresponding to frq of cones of eyes, you can recreate the illusion of white. But if you want to change the spectrum, you need some sort of non-linear convertion. White LEDs use a phosphor to change spectrum of another LED of shorter wavelength, like blue or UV.

A monitor CRT (at least) has for so far I know Red green and blue pixels but no yellow and as we all know by changing the intensity of the pixels one can see all colors.

You forgot the blue, remember the acronym RGB. Do a search for vectorscope in contexte of TV repair. RGB are used to encode a polar vector of chrominance, the angle is the hue, amplitude is saturation.

Mathematical I think it impossible to just by changing amplitude changing the frequency.

Exact, you need a nonlinear element to change the spectral content.

ETA: Better to read article on Vectorscope, been a long time since doing this stuff, TVs were still using vacuum tubes. No longer remembering correct terminology!

a reply to: Cofactor

Thanks for helping me out couldnt solve this even duckducking gave no result... this was exactly my problem...

...you can recreate the illusion of white...

Well I hoped for that answer , so we percieve 3 discrete frequencies of light from a monitor (blue included).Mathematical a tried to solve it to create 3 sine waves with 3 frequencies in (audacity sound program) . However when I did a fourier transform in it it gave a continuu spectrum. I Guess it interpolated the frequencies.

For me quite important so I am mostly exposed to only 3 discrete colors all day and never yellow .. although my brain tells me otherwise.

MyBrain You're are a Liar

a reply to: frenchfries

Mathematical a tried to solve it to create 3 sine waves with 3 frequencies in (audacity sound program) . However when I did a fourier transform in it it gave a continuu spectrum.

The whole point of Fourier transform is that for an infinite windows, there exist a correspondance between time representation and frequency representation for a signal. If you go for engineering studies, you will find that understanding a system is MUCH easier when using the frequency domain.

In real world, FFT are used since we have discrete points of sampling for the signal, but similar if we exclude the effect of discrete sampling and windowing.

If you add 3 sines together and your system is linear, then only 3 sines exist. In practice, going from the nice formula you find in a book to the actual display of a spectrum analyser is VERY frustrating for the beginner. Math frq spectra are often represented with one side being the complex numbers part, and the other side the real number part. You need to fold the spectra to get a real life magnitude spectra.

a reply to: Cofactor

hmmm.... Indeed fourier with it's frequency / amplitude domain I understand better.

If you add 3 sines together and your system is linear, then only 3 sines exist

.

As a kid I made some FFT transformer in pascal once (I download some code) tweaked it. And I remember that in experimenting , Threw in some sampling points and was very confused.... ?!

Had to learn about complex numbers first. huh root minus 1 ? Gauss must have been very smart.
Had to multiply the complex numbers also got a phase shift as a bonus. Not that I understood all I did but it was fun , i ended up with a very buggy soundcompressor... aahhh ... win95 dialup internet ...time flys...
Also Later as a student I used FFT in a project to analyse movement patterns of animals in a zoo.
FFT is a very cool scientific tool.

a reply to: frenchfries

You have made codes in Pascal. You come from a glorious time. I also did coding in Pascal Object, called Delphi at the time if I remember well. I loved the way we could easily and rapidly make a very descent GUI based program under Windows with Pascal being a very aceptable language for technical task.

a reply to: Cofactor

oh well that's also a bit my geekcode to. Turbo pascal and then delphi. Made some projects and made money with it. Later I ditched the Microsoft windows for linux , because I couldn't stand the NSA key in it ATS thanks
Now with regards to pascal I use the lazarus gui. But those old days were the most glorious times so much fun.

In a way less restricted than now or is it just me getting old and sentimental ,nah

a reply to: frenchfries
Not sure it was Turbo Pascal or Turbo C, but remember doing some work that required two floppy drive to avoid never ending request to change disc. The BIN floppy in A: and the LIB floppy in B: . Even me have a hard time to believe it was possible to use a computer without a HD.

a reply to: frenchfries

That's an interesting question. Never thought of that.

Looked it up. This prob explains it:

link

a reply to: nOraKat


Very interesting indeed...I summarize..

When an animal sees a computer screen, it doesn’t see the same colours as you do because our monitors only properly work for humans.

I never considered that animals would see something completely different... based on the resolution of the eyes..
My old cat used to chase the mousepointer... Young kittens nowadays , well they don't ( maybe because the CRT monitor is replaced by a LED version )

When your computer screen is told to produce a certain colour, it chooses the red-green-blue ratio that is the closest in
terms of activated cones to the one the given colour would normally cause.

So we give our eye only the light the cones want... For other frequencies there is complete darkness.. at least concerning the light of the monitor.

They still see the same shapes, but the colours may be completely off. I wonder whether scientists who study cognitive abilities of animals by showing them pictures even realize that…

Bananas are yellow... no yellow in RGB... could be some animals get confused. Any way very interesting.

source

Greetings.

a reply to: frenchfries

I never considered that animals would see something completely different... based on the resolution of the eyes.. My old cat used to chase the mousepointer...

Cats must see similar to us because if I put on a video with birds and squirrels my cats will sit there and watch it for long time. They might even walk up and try to catch one, or look behind the screen to see if the bird is there.

a reply to: Cofactor

I remember that it was probable Turbo C because I started to dislike it of that diskjockeying .

Lol I begged my father to buy a HD. 5MB he said no. And because of pure frustration i started to mess around with the io.sys of the boot floppy. to access hidden sectors and turn 1.44m into 1.8m oh I killed that floppydrive. As a result I was rewarded a HD , bad parenting but well the kid (me) was happy.

a reply to: nOraKat

oh .. but then you have to turn of the sound i guess, Because they might only hear it. Will you do that ? Tell me the reaction please. Because My kitten doesn't react on anything on the screen.

a reply to: frenchfries

Yup, he's checking it out, with or without sound.

Try 'Winter birds' on Youtube

a reply to: frenchfries

There are quite a few screens with a dedicated yellow diode/pixel now - RGBY.

My dog reacts to critters on screen before and after we switched from Tube to LCD. Particularly footage of lions stalking prey. She mimics their behavior when we come across squirrels on walks.

She learned to stalk prey from Nat Geo.

a reply to: nOraKat

So , cats see more or less colors the same as we cool thats solved. Maybe my kitten needs glasses

a reply to: MuonToGluon

RGBY ha just searched it... Might have better quality of colors.

hmmm.... So than we have now to kinds of yellow the real one and the composed one..

Call them rugby monitors. If so, then HTML coders and computer programmers will have to put up with a new color coding scheme. Instead of #FFFF00 to get yellow you’ll be writing #000000FF to get yellow. Or write #FFFF00FF to get super yellow! By the way, adding 256 more values for the various shades of yellow on an RGBY monitor means that the monitors will be capable of producing over four billion individual colors.

a reply to: intrptr

lol dangerous dog squirrels beware the dog, animals get really smart these days.

originally posted by: frenchfries
a reply to: intrptr

lol dangerous dog squirrels beware the dog, animals get really smart these days.

Not to worry, shes not quick enough. It is instinctual for her breed to hunt. She just never learned to stalk before until she saw it on TV.