Ferlin

How do you {apply} clouds difference to each different channel. I'm sorry but Im new to photoshop and for some reason I am intimidated
by channels. I just hav'ent seen much use for them so far but I want to start using them . I'll have to read more about them.
Wendy - you stole my thunder. The first object that I want to make that looks real - is a lava lamp. Using some of Marks tutorials I want to try it. Never made a real looking object before on my own.
Photoshop is a stone groove baby! Yeah! B7

Bacardi

When you have Photoshop in, say, RGB mode, this means that all colours have to be a mixture of Red, Green and Blue. The easiest way to do this is to superpose three images: one with the Red settings for each pixel, one for the Green and one for the Blue. These images need no specific colour, only intensities, so they are usually shown in grayscale, and behave as greyscale images, meaning that you can apply lots of filters, levels, curves, invert etc to them. These three greyscale images/intensity maps are called channels.
For a uniform grey image, all pixels have the same value. grey means the same amount of Red, Green and Blue. Medium grey is the grey that is in the center between black and white.
So a document that is uniformely filled with medium grey will give three channels that are identical, and which are also filled with medium grey. (all three values of R,G and B are the same, and this for all pixels).
When you go to the channels palette, you can have the xomposite channel active (it works like the layers palette), or one of the R,G or B channels. Activate the Red channel by clicking on it and apply filters>render>clouds on it, whilst having the eye icon on the composite channel. You'll see red clouds appear. Do the same for Green and then for Blue.
You can, of course, also apply other filters, etc, just as you fancy.

When returning to the layers palette, don't forget to set the composite channel to active.

You can try this one also with CMYK (four channels) or even LAB. LAB is my favourite for many things as it contains much information (colours) that a monitor cannot show, but that PS can calculate anyway.

Channels offer another great trick, namely that you can load them as selections, but that is for a next time.

Wendy: 8}

Ferlin

I feel like a creep-wipe. I did'nt think your explanation would have to be so involved and I feel guilty. Your explanation is very clear and I understand it and have printed it out for future reference.
I've only used channels for saving selections and have got used to using layer masks for masking and difficult selections. Channels are my next move in my photoshop addiction - obsession .
Thanks again [righton]
Ferlin

Rick

Good stuff Erik -although I,m not sure what you meat about setting the composite channel to active [confused]

However here are a couple of coloured cloud images I did with your method

Bacardi

When you open the channels palette in RGB mode, you will find the three channels for R, G and B, and on top of those the channel that combines these three. In fact, it's not a real channel.
With the eye icon, you can turn each one on and off, but you can have the eye icon on for the composite channel, resulting in a view of all three channels together or your umage as you know it and still have another channel highlighted or active, resulting in changes that are limited to this channel's information, be that R, G or B.
So when, in this situation, you go back to your layers palette and apply any new thing like a filter or levels, or invert, it will be limited to that active, highlighted channel. That is why you need to highlight the composite channel so as to make it active. Unless of course, you want to apply any effect to that chosen channel only.

Hanarky

why do my colors looks so washed out and not clear and bright like in the other examples?

I made a layer, filled it with 50% gray, made a channel out of it and then applied the clouds filter on each of the 3 channels, each channel with another color combination. It looked washed out. I made another layer, like wbiss wrote and did the same again and set that layer to differenz-mode. Still washed out. What do I miss |

Hanarky

forget my question above, please [saywhat]
We are in grey mode in the channel and I can't apply color to it. Stupid me, lol. So the same again, but this time the first layer with clouds and the second layer with difference clouds and set to differenz. Wow, what colors!

P.S. Can I remove posted pics again and if so, how?

Bacardi

Because channels are like greyscale images. The darkest colour one can get is black, and the lightest is white. So whatever other colour you choose as darkest hue will always be lighter than black, and any colour you choose as lightest one will inevitably be darker than white.
So fill each channel with black and white clouds and you will have more contrast.

note: in the preferences you can choose to set the way you see these channels to their colour, meaning that instead of grey, you would see resp. Reds, Greens and Blues, ranging from darkest to lightest. But no specialist would ever encourage to use this option as human eyes are far more sensitive to green than to dark red, and also because in CMYK the yellow channel would be difficult to see. Also, when all colour values are represented by greys, it is easy to compare one to another.

recap:

1/ colour is built up from a basic set. For light this is RG and B, for print this is (mostly) CMYK.
2/ each basic colour is kept/remembered separately in a container called a channel.
3/ each channel can store hues for its colour that go from the darkest to the lightest.
4/because channels contain information on every pixel of the image, andthat information is kept on exactly the same spot as the pixel is in the image, channels are exactly as big as the image and can be made visible as monochromatic (one-coloured) images.
5/ instead of using the colours contained in their resp. channels, they are made visible as greyscale images, and this for practical reasons.
6/when one adds the information of all colour channels for any specific spot on the image, the monitor/printer knows exactly for each pixel how much of each basic colour has to be applied, and we get all possible hues.

markzebra

The best way to think of this is to try and seperate colour from luminosity. Color is the RANGE of hues. luminosity is the brightness of those hues.

By seperating your file into LAB mode- you can perform random operations using clouds on either the Colour or Brightness, seperately

So the point I'm making is this?? to get a truly random color variation across the surface perform clouds on both the L and B channels. This will give you a complete randomly generated spectrum (for it to cover the full spectrum hold down option as you choose Clouds from the filter menu). Because the result of this has no depth of tonal variation, it may not be what your really looking for, but this is the best and most complete answer to the original question

If you also want the Lightness to vary, use clouds on the L channel.

Black Lightning

well im glad to see some different, yet simular, methods on how to do this. thanks for your help guys. [oops]

wbiss

B7 This is the kind of stuff... you don't find in books!

Great detailed and concise explanations Erik! You have a 'knack' for simplifying a complex subject. Thanks for taking the time to give of your time by detailing your knowledge in such a way that we can all understand! :} [righton]

markzebra... I will definitely have to play more (based on your remarks) in the LAB mode! [righton] Thanks for your very knowledgeable and valuable contribution to this thread too! :}