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Author Topic: about light and color, primary colors  (Read 4941 times)

Offline brynn

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about light and color, primary colors
« on: January 10, 2014, 01:51:39 PM »
Hi Friends,
As I've mentioned in my first few posts here, I'm about to buy my 1st dslr.  And aside from online shopping, and soon in-store shopping, I've been trying to learn whatever I might need to know, to finally get serious about photography.  Someone posted this link for me (in another topic) and I just started reading it.  http://johnlind.tripod.com/science/scienceframe.html

On this page, http://johnlind.tripod.com/science/sciencelight.html#Light, it says that the 3 primary colors are red, green and blue.  I guess rgb are the primary colors of light?  Because in my school-days art classes, I was taught the primary colors are red, yellow and blue.  But I guess ryb are the primary colors of paint or other media....or something like that?  As I was taught, green can't be primary, because it's made by mixing yellow and blue.

And I realize this is a fairly technical question, and that the answer might be too technical (for me) to understand completely.  But I would like to try to understand how/why the primary colors of light are different from the primary colors of....well, I thought ryb were the only primary colors in the world.

I do know that TVs or computer monitors (e.g.) use the RGB pixels, but I didn't realize they were called primary.  I wonder why they can't (or maybe just don't) use yellow instead of green?  And I can't seem to reconcile with what I learned as primary colors: red, yellow, blue.  Can someone explain this in relatively simple terms?  Or if it's too complex, maybe someone can link me to an article or something?  Normally I would just search for myself, but I can't seem to come up with the proper words to search.  Maybe red, yellow and blue are the primary colors that our eyes can see?  Or something like that?

And one reason that I really want to try and get a handle on it, is because I wonder if this discrepancy will come into play with photo editing?  Some of you have impressed upon me how much editing is routinely done to photos these days.  And thinking in terms of rgb, instead of ryb, for editing.....well, it could be a challenge to change my habits, with graphics programs.  For example, if yellow is not primary, what 2 colors do you mix, to make yellow?  I don't think you can.....  .....Or maybe this is really a non-issue, as far as photo editing?  Maybe the color of the light only matters during the taking of the photo, the light entering the camera?

Thanks for your help  :)



Offline ABERS

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Re: about light and color, primary colors
« Reply #1 on: January 10, 2014, 02:31:49 PM »
Bryn

Without appearing rude, can I make a suggestion. Go out and buy your DSLR and learn on the job. All your questions will have no bearing on what type of photography you take or want to take.

I have yet to meet a photographer that needed to know all the answers to the questions you pose to be able to take a reasonable picture. They progress by a hands on approach and usually by making many mistakes and make progress that way,albeit slowly but certainly surely.




Offline donoreo

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Re: about light and color, primary colors
« Reply #2 on: January 10, 2014, 02:34:26 PM »
I agree.  You are over thinking.  I have never given any thought to any of that and do not know anyone who has.  The largest concern with colour and photography is colour temperature.   

Offline Beaux Reflets

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Re: about light and color, primary colors
« Reply #3 on: January 10, 2014, 03:10:09 PM »
Red Green Blue are the primary colours and the art teacher perhaps should have explained as mine did, that for the purpose of painting or colouring with pigments yellow is used instead of green.

The easiest way to demonstrate this is; If you fetch a dried brown leaf from the garden (which has naturally turned brown by the combination or mix in green and red pigmentation) and place it over a White torch light (an LED one will do) the brown leaf now looks or appears to be in shades of Yellows.

As others have intimated, find a camera that feels comfortable to use and jump in  ;)  Photography is a lot of fun and a never ceasing adventure in learning to enjoy.  :tup:
« Last Edit: January 10, 2014, 03:21:58 PM by Beaux Reflets »
:beer: Andy

"Light anchors things in place and gives perspective meaning."

The choices we make are rooted in reflection.

http://beauxreflets.blogspot.com/

Offline StephenBatey

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Re: about light and color, primary colors
« Reply #4 on: January 10, 2014, 03:36:15 PM »
It's the difference between additive and subtractive colours.

Our eyes are sensitive to just three colour bands - red, green and blue - and our minds make up all the myriad shades. If you mix equal amounts of light of the three primaries, you get white. This is additive colour, because you're adding in light of different colours.

When we "see" a red object, it appears red because it reflects red and absorbs green and blue. The same with paints - they get their colour from what they don't absorb. So, if you mix red, green and blue paints, you get black, not white - or you would if the paints were pure colours.

This is why the result of mixing paints differs from what happens when you mix light beams. With paints, you can't "make" yellow because it's the addition of red and green light that gives it; there are no paints that you can mix that will result in the absorption of blue and reflectance of red and green except yellow itself (because yellow is red + green).

Edit to add: hopefully the chapter on light in my book will make it clearer - if longer winded!
« Last Edit: January 10, 2014, 03:37:38 PM by StephenBatey »

Offline Graham

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Re: about light and color, primary colors
« Reply #5 on: January 10, 2014, 04:08:54 PM »
  I think that the technical answers to your question should clarify the matter and I can see why you are curious, but as Alan says, don't run of with the idea that you need to understand this to be a good photographer.
                             Graham.  :tup:
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Offline Oldboy

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Re: about light and color, primary colors
« Reply #6 on: January 10, 2014, 06:59:26 PM »
Agree with Abers, forget colour theory, as you don't need to know it to take great photos.  :D

Offline SimonW

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Re: about light and color, primary colors
« Reply #7 on: January 10, 2014, 07:11:38 PM »
This week's Amateur Photographer Magazine (dated 11th January) has a very technical article by Professor Bob Newman about colour. Essentially the "Primary Colours" we know do not tell the whole story, for example mixing red and green should produce a colour we cannot see. Colours can be reproduced by monitoring only two of those three, and luminance - and some camera sensors do it that way. Human eyes have sensors known as rods and cones. Some birds and animals have less than us, some more, and some can see many more colours than we can (not simply UV or IR). I was totally baffled by the science and decided it would make no difference to my photography even if I could understand it. (And some of the above might reflect my lack of understanding.).

Read it if you want to be completely baffled!

Simon
« Last Edit: January 10, 2014, 07:12:36 PM by SimonW »
Simon Warren
(in Dunning, Scotland)

Offline StephenBatey

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Re: about light and color, primary colors
« Reply #8 on: January 10, 2014, 09:30:07 PM »
Well, strictly speaking, colours are a figment of our imaginations; all that exists in the real world are different wavelengths of light. I haven't read or seen the article, but at a guess it would be referencing the CIE chromaticity diagram, which does in fact depend on non existant colours to produce a working theoretical system (it needs negative light to make it work).

I'm less convinced that you don't need to know some colour theory if you want to be a good photographer. OK, I don't need a lot since I photograph using black and white film (but you still need some knowledge to understand which filters to use). For a colour photographer, there is the rather important point that just as our eyes don't see all the available colours (translate that to "give us the same sensation of colour when different inputs are presented" - rather important to understand metamerism and why a lot of B&W inkjet prints change colour depending on the light source, being B&W only either in daylight or in artificial light and purple or green in the alternate light source) and neither can any medium reproduce them all.

Knowing what won't appear on our monitors, or what can't be reproduced with a particular paper or ink set, or what can't be reproduced in print, should matter if you want to have complete control over what you are producing. I do; but I'm well aware that for many "good enough" or "it looks OK" is all that matters. To me, knowing why something happens lets me, if not control something, at least use it to my advantage. Note - this is not at all the same as profiling your camera/scanner/printer. It's referring to an absolute limitation of what it is physically possible to do.

Offline Oldboy

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Re: about light and color, primary colors
« Reply #9 on: January 10, 2014, 09:51:29 PM »
Well, strictly speaking, colours are a figment of our imaginations; all that exists in the real world are different wavelengths of light.

Well that's not strictly true either, as colour is determined by the amount of enegy each proton has.  8)

Offline StephenBatey

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Re: about light and color, primary colors
« Reply #10 on: January 10, 2014, 10:06:00 PM »
The amount of energy determines the wavelength (and I'm not getting involved in the "what is light" debate), so I was accurate. You might want to use the wave/particle duality to argue that the amount of energy determines how our minds process the information; but in no sense does energy have a colour except in our minds.

Offline Oldboy

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Re: about light and color, primary colors
« Reply #11 on: January 10, 2014, 11:56:53 PM »
The amount of energy determines the wavelength (and I'm not getting involved in the "what is light" debate), so I was accurate. You might want to use the wave/particle duality to argue that the amount of energy determines how our minds process the information; but in no sense does energy have a colour except in our minds.

Then perhaps you can explain this?

Daily observations of color can be related to spectroscopy. Neon lighting is a direct application of atomic spectroscopy. Neon and other noble gases have characteristic emission frequencies (colors). Neon lamps use collision of electrons with the gas to excite these emissions. Inks, dyes and paints include chemical compounds selected for their spectral characteristics in order to generate specific colors and hues. A commonly encountered molecular spectrum is that of nitrogen dioxide. Gaseous nitrogen dioxide has a characteristic red absorption feature, and this gives air polluted with nitrogen dioxide a reddish brown color. Rayleigh scattering is a spectroscopic scattering phenomenon that accounts for the color of the sky.  ???

Offline StephenBatey

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Re: about light and color, primary colors
« Reply #12 on: January 11, 2014, 04:00:51 PM »
What's to explain? It seems self explanatory, and completely irrelevant to anything I wrote, although I wouldn't have phrased parts of it in the way given. Or did you mean that whoever wrote it refers to the subjective sensation of "colour" without using the word subjective? Most people do this - very few people for example would refer to the "subjective pain" of toothache, and just use the word "pain". ???

If you want to get technical (and I don't) there's a very simple relationship between energy and frequency. Energy = frequency multiplied by Planck's constant, from which you can calculate one given the other.

Offline Andrew

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Re: about light and color, primary colors
« Reply #13 on: January 12, 2014, 07:42:42 PM »
Bloody hell - have i been doing it wrong for all these years?

So how does all this stuff square with B&W images - or should I really refer to them as 'greyscale' based images?

I can understand the curiosity to the question as a nice to know - and that's good. But it really has no relevance to what camera you buy or picture you take.

You 'see' or 'create' the shot.
Set up you camera to 'capture' or 'record' the scene
Process the image and present it to the desired audience (processing could just be in camera, printer or on computer - presented could be on a web site, a print, canvas, mug etc)

To my knowledge, ALL digital cameras shoot in colour. If you opt to 'shoot in B&W' camera still shoots in colour buts shows you images that have been processed to look as a B&W image would look exporting as such. But if you look at the RAW file - it will still be in colour  :tup:

Now that could be confusing to some one looking to buy their first camera  ???
1 body, 1 lens, 1 flash gun, 1 tripod, 1 cable release & 1 filter. Keeping it simple!
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Offline StephenBatey

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Re: about light and color, primary colors
« Reply #14 on: January 12, 2014, 08:01:19 PM »
How does this relate to B&W? Read up on contrast filters and find out.

How do you "see" if you don't know what the camera is capable of recording, or your monitor of displaying or your printer of printing? If you don't know, at best it's a pious hope or blind luck. I prefer to create based on a greater level of certainty than that.

And, no, not all digital cameras record in colour.

 

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