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Author Topic: visibility of colors  (Read 5004 times)

Offline science_guy

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visibility of colors
« on: 13/07/2006 18:31:25 »
I was looking at a few colors in low light, and i noticed that the orange color appeared to be red, while the green color appeared to be blue.  Are certain colors easier to see in low light?  What I saw led me to believe that of the main color group, red, blue and yellow, yellow is the hardest to see in low light.  Is this a valid conclusion?

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another_someone

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Re: visibility of colors
« Reply #1 on: 14/07/2006 01:40:04 »
There are two separate answers to this.

Firstly, the eye has two different colour receptors, the cones and the rods.  The cones come in 3 types (assuming you do not suffer from colour blindness), these are normally regarded as red, green, and blue (although the true colours do not match exactly those labels).  These cones are responsible for colour vision.  The rods only come in blue (although not exactly the same blue as the blue cone), but they are capable of low light vision at levels of light where the cones do not respond well.  You will also find more cones near the centre of your field of vision, so your colour vision is better in this area, whereas the rods are more evenly distributed.

The other factor is the colour of the light source.  Different light sources come in different colours, and this can distort the apparent colour of what you are looking at.  The noonday sun is fairly blue in colour (normally it is regarded as having a colour temperature of 6500K, whereas sunset and sunrise can be around 1600k, and domestic lighting is normally expected to be around 2500K to 3500K.  The colour of what you are looking at will always depend upon the colour of the light source (this can be a major problem in photography when you have mixed light sources with different colours).

http://en.wikipedia.org/wiki/Color_temperature
quote:


  • 1600 K: sunrise and sunset

  • 1800 K: a candle

  • 2800 K: tungsten lamp (ordinary household bulb)

  • 3200 K: studio lamps, photofloods,

  • 5000 K: A designation of D50 stands for "Daylight 5000K" and is the most common standard for professional light booths for photography, graphic arts, and other purposes.

  • 5200 K: bright midday sun.

  • 5500 K: average daylight, electronic flash.

  • 6000 K: lightly overcast sky

  • 6500 K: heavily overcast sky

  • 8000 K: hazy sky

  • 20000 K: deep blue clear sky









George
 

Offline heikki

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Re: visibility of colors
« Reply #2 on: 15/07/2006 12:22:36 »
quote:
Originally posted by science_guy

I was looking at a few colors in low light, and i noticed that the orange color appeared to be red, while the green color appeared to be blue.  Are certain colors easier to see in low light?  What I saw led me to believe that of the main color group, red, blue and yellow, yellow is the hardest to see in low light.  Is this a valid conclusion?




:)

Hi.

What to we need to see colors?

1. Object.
2. Light.
3. Eyes+brain.

1. Object has those colors.
Like animals, trees, clouds, blue air-atmosphere, painting colors, etc.

2. We need light that we can see these colors.

3. Colors must fly to our eyes and goes trough eyes to our brain so our mind can see it.

When i put front of my eyes paper i dont see colors of object. Colors dont come through that paper. Radiowaves vibration comes.
When i put front of my eyes 10meter air-matter colors can come through that matter.


Therefore i make question.

Maybe colors is some kind of small matter-particle stuff motion like photons are? Smaller particle size than we yet understand.

:)
 

another_someone

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Re: visibility of colors
« Reply #3 on: 17/07/2006 00:47:45 »
In simple terms, colour is to light like a musical note is to sound each colour is like a different note.  Colour is a measure of the energy of a photon, so a photon that we see as having the colour blue has more energy than a photo that we see as the colour red.

The differences between colour and sound are partly because our ears have receptors for thousands of different frequencies of sound, whereas our eyes only have receptors for 3 or 4 colours of ligt, so all the other colours have to be approximated.  That is why if you mix blue and green, you see cyan the actual light has not changed from blue and green to be cyan, it is just that our eyes cannot properly see that it is two separate colours, and so it guesses that it is one colour that is somewhere between blue and green.  In this respect, it is different from out ears, because our ears can separate thousands of different sounds, so if you mix two notes, the ear will still hear two separate notes, not a single note that is somewhere between those two separate notes.



George
 

Offline eric l

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Re: visibility of colors
« Reply #4 on: 07/08/2006 13:02:55 »
There are many aspects to colour perception.
First there is the purely physical aspect :  visible light is electromagnetic radiation within a given range of wavelengths (from about 400 to about 750 namometer), and each wavelength is seen a
specific colour.
Then there is the fysiological aspect :  the eye does not determine the wavelength, but gets information from 3 types of cones.  Each type of cone has its maximum sensitiviy for one wavelength :  about 430 nm (S-type, blue), about 515 nm (M-type, green) and about 565 nm (L-type, red).  Sensitivity for other wavelenghts around these values shows something like a Gauss-curve (bell shaped curve).  The information sent by the eye to the brain will give a ratio of S, M and L values.  
The light reflected by any object will depend on the light falling on the object, and that's where the colour temperature of the light, mentioned by George, becomes important.  Il the light from the source contains less blue, the S-type cone will not be stimulated as much as with a light with a high colour temperature.
The brain can correct the information, but within limits.  In order the judge the colour of a piece of textile or a print one needs either daylight or a set of different lamps.
 

ROBERT

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Re: visibility of colors
« Reply #5 on: 07/08/2006 17:43:39 »
quote:
Originally posted by science_guy

I was looking at a few colors in low light, and i noticed that the orange color appeared to be red, while the green color appeared to be blue.  Are certain colors easier to see in low light?  What I saw led me to believe that of the main color group, red, blue and yellow, yellow is the hardest to see in low light.  Is this a valid conclusion


" In color vision, the color experience of a given light mixture may vary with absolute luminosity, because both rods and cones are active at once in the eye, with each having different colour curves, and rods taking over gradually from cones as the brightness of the scene is reduced. This effect leads to a change in colour rendition with absolute illumination levels that can be summarised in the Kruithof curve, named after A. A. Kruithof.

As the brightness of the scene decreases the brighntess of red colours decreases more rapidly than those of blue colours, this is the so called Purkinje effect."

http://en.wikipedia.org/wiki/Kruithof_curve
« Last Edit: 07/08/2006 17:47:08 by ROBERT »
 

Offline Soul Surfer

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Re: visibility of colors
« Reply #6 on: 09/08/2006 21:48:40 »
There is one other important aspect to colour vision in addition to those already mentioned  the brain interprets colour by observing the difference in response between the three different colour sensitive cones to light reflected from the object.  this means that it is possible tyo see the colur blue on a blue object when there is in fact no blue light in the illuminating source.

old fashioned low pressure sodium lamps have an intense yellow colour and everything appears in black and yellow.  modern high pressure sodium lamps have a more golden light because the pressure tuns the narrow yellow lines into a broader band of frequencies in the yellow region of the spectrum.  It is possible to see "colours" in this light although they look rather weak and washed out  however the only light present is a small range of the yellow spectrum.

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Re: visibility of colors
« Reply #6 on: 09/08/2006 21:48:40 »

 

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