Subtractive Colour Mixing

[maxjones2000]

Right, I thought I understood it, but I've hit a wall!!

 

When you add a cyan & a yellow filter in front of a white light, you are subtracting everything other than cyan and yellow from the spectrum. Effectively, this is subtracting everything other than green, blue (green + blue = cyan) and red (red + green = yellow), so you are subtracting everything other than RGB, making white. However, cyan and yellow dont make white... :P

 

Am I just being dense, or I have I missed something?? :D

[AndyJones]

In subtractive colour mixing you have three colours. CMY (cyan, yellow and magenta) When you put cyan and magenta in front of the lamp you will get Green. if you then add magenta you will get no light output. Maybe you were missing the third colour?

[MarkPAman]

When you add a cyan & a yellow filter in front of a white light, you are subtracting everything other than cyan and yellow from the spectrum.

No, that bit's wrong.

 

You're subtracting everything other than cyan, then you're subtracting everything other than yellow from that. Can you work it through from there?

[niclights]

Forget about the whole RGB part.

 

In simple terms C+M+Y = White.

[AndyJones]

Forget about the whole RGB part.

 

In simple terms C+M+Y = White.

surely C + M + Y = Black ? :P

[abbotsmike]

Forget about the whole RGB part.

 

In simple terms C+M+Y = White.

surely C + M + Y = Black ? :P

In terms of filters, yes. In terms of light, CMY = white!

[maxjones2000]

When you add a cyan & a yellow filter in front of a white light, you are subtracting everything other than cyan and yellow from the spectrum.

No, that bit's wrong.

 

You're subtracting everything other than cyan, then you're subtracting everything other than yellow from that. Can you work it through from there?

 

aha!! That makes sense now!! Thanks!!

 

 

Thankyou everyone! Finally understand it now...hopefully! :P

[mac.calder]

The easiest way to illustrate subtractive mixing is to look at the colour transmission diagrams (I grabbed LB06 (lagoon 6) and L101 (Yellow) transmission diagrams from the Lee Swatchball)

 

http://i21.photobucket.com/albums/b273/maccalder/101.jpg

Lee 101

 

http://i21.photobucket.com/albums/b273/maccalder/b06.jpg

Lee B06

 

These diagrams show that white light (lets pretend white light is a completely even mix of every wavelength) when pushed through these filters has everything removed, except for the bit under the black line.

 

http://i21.photobucket.com/albums/b273/maccalder/CMY.jpg

The two placed into photoshop over each other then illustrate the resulting transmission (It is the overlap between the two lines) - a nice green

 

Light is not made up of 3 colours. The three colours thing is an overly simple way of explaining light to people who just want to know the basics... If you were to take just Cyan, just Magenta, just Yellow (the lee "magic" series) which only allowed transmission of their respective colours in a rather narrow band (and were perfect in doing so) then perform subtractive mixing of any two colours, you would end up with black

 

http://i21.photobucket.com/albums/b273/maccalder/CMY2.jpg

 

(This explanation is also overly simplified, purely to illustrate concepts)

[sleah]

To throw in something else, am I right in thinking that subtractive mixing would be where you put one or more filters in the same lantern, whereas additive mixing is where you would shine one or more coloured light sources at the same spot.

So.... (in simple terms) if you put red, green and blue filters in the same lantern, you would block the light effectively as you are subtracting the three primary colours. (Black light anyone? :P )

If you shine three lights, one red, one green and one blue at the same spot you would get white light as you are adding the three primaries????

[Gerry]

10/10, correct, go to the top of the class.

 

Cheers

Gerry

[dbuckley]

Google for and download visual color picker (I've got v2.6, don't know how young or old that is) and that'll let you play with RGB vs CMY.

[maxjones2000]

Ok, I'm even more confused now!! Here's what I put in my work, is this right?

 

Single colours:

When you add a magenta filter in front of a white light/full spectrum, it will filter out everything other than magenta, which is made up of Red and Blue (red + blue = magenta), therefore effectively filtering out green from the spectrum (e.g. SUBTRACTING green from the spectrum).

 

Multiple colours:

When you add a cyan & a magenta filter in front of a white light source, firstly everything other than cyan is filtered out (apart from cyan – blue and green), and then when the light goes through the magenta filter, everything other than blue passes through, as blue is the only primary colour that makes up magenta that passed through the cyan filter.

 

Light Source

Cyan Filter

Magenta Filter

 

heres a link to the photo/image that I used to explain multiple filters:

http://www.flickr.com/photos/maxjones2000/5117323182/

 

Is that right? I know people said to ignore the RGB aspect, but its just something that interests me so its really annoying if I cant understand the 'whole' thing!! Yes, I know thats sad... :P

 

 

Google for and download visual color picker (I've got v2.6, don't know how young or old that is) and that'll let you play with RGB vs CMY.

 

Thanks David, I'l have a look at that! Could come in useful!! :P :P

 

By the way, I have no idea whats going on with the middle bit of this post (ie the [size3] bit), so just ignore that!! It wont let me get rid of it :D

 

Moderation: Fixed the formatting and got rid of the "size 3" bit for you :)

[madorangepanda]

CMY does not equal RGB.

 

Do not think of them in terms of Cyan = Blue and Green etc

 

A cyan filter only lets cyan light through, a red filter only lets red through.

 

Additive mixing is if you have 3 (or more in some cases) separate coloured sources. Adding CMY sources together gives white. As does adding RGB together.

 

Subtractive mixing is if you have a white source and you take out all of the colours you don't want. Ie putting a red gel in front only lets red through, a cyan gel would let cyan through.

[maxjones2000]

CMY does not equal RGB.

 

Do not think of them in terms of Cyan = Blue and Green etc

 

A cyan filter only lets cyan light through, a red filter only lets red through.

 

Additive mixing is if you have 3 (or more in some cases) separate coloured sources. Adding CMY sources together gives white. As does adding RGB together.

 

Subtractive mixing is if you have a white source and you take out all of the colours you don't want. Ie putting a red gel in front only lets red through, a cyan gel would let cyan through.

 

Oh ok thanks!! So additive is adding different sources of coloured light (i.e. LED fixtures are additive because you are adding different coloured LED's together to make one colour), and subtractive is subtracting colours from white light using gels (ie CMY mixing works by using dichronic gels).

 

I get it now!!!! Thanks everyone!! :D :P

[TomHoward]

Does anyone actually use subtractive colour mixing in a real-world application? And I missing a whole branch of design of putting multiple colours in a lantern?