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Channels


Tron

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I know that using channels in PS should one of the basics, however I have never really gotten into them. One most of the site I see re: moving Poser images into PS, they talk about saveing the figure as a alpha channel- so that the background can be cleanly removed.
I would appreciate a little instruction on how to do this if anyone can help [confused]
 

{OZ}

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Rick, to do that you have to export your model

File->Export-> Image

from the dialog box save as type choose Photoshop uncompressed.

when you open that psd in photoshop, you see that the Alpha channel is created for you.

on layers palette, double click on where it says background, hit ok. it should say Layer 0.

click on your Channels tab then CTRL click on the Alpha1 channel.

then from the Layer Menu
Layer -> Add Layer Mask -> Reveal Selection

then go back to your Layers tab. Hold CTRL and click on the small box underneath the layers tab (Create New Layer). That should create a new layer under your Layer 0.

then you can fill that layer with whatever you want! :)

I hope that helps

OZ

:)
 

Tron

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Wow that easy, thanks Oz and Mark you uys have made my life so much easier thank you thank you.

It works too
see
 

Tron

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I wonder guys after the Poser figure is transplanted into PS, should there be a little feather or blur applied to make him blend a little better ? I wanted this guy to stand out, so all I did was to use the rubber stamp tool to pick up a little of the backgroud texture and blend ito his feet to give him the impression of actually being there. There must be a few other tips to help make the imported image a part of the background

Thanks again

Buy ther way Oz your instruction worked perfectly for me unitil the part about Ctr click on the 'create new layer icon' when I did that I got an adjustment layer, so I just created a new layer and moved in down under the imported layer and the merged the two layers together and used the rubber stamp as i said above.
 

Erik

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Bizarre as it may seem, Rick, I would definately use a desat on the poor creature just to merge it more with the background.
Now it stands a bit apart...

A bit about channels. More will come later...

When you work in RGB, your image is composed of three separate groups of information. Red Green and Blue each have for each pixel in your image a specific brightness value out of a set of 256. Together these make your colour. (255,255,255 is all three at maximum which gives white; 0,0,0 is all three off which gives black; 255,0,0 gives pure Red, etc...)

Each of this groups of information is called a channel, and because each pixel is influenced, they are visible like images with 256 possible brightness values, that is: as greyscale images. Channels behave as greyscale images: you can use filters and adjustment on them.

So in your layers palette you can get a thumbnail view of each channel. You can also select one to make it visible by clicking on that eye icon. The top "channel" is the composite one which is not really a channel, but is used to show your image in full colour.

So the eye icon makes a channel visible, but clicking on its name selects it, which means that you can work on it.
Try this: open a white RGB doc. Make one channel visible and see that it's selected. You'll see the greyscale image on your monitor(in this case: pure white). Invert it (Image>Adjust>Invert). Now make the composite back visible by clicking on the top eye-icon. See?
Try this: keep the composite channel visible (eye-icon on) but select for example the blue channel. You see the full colour image on your monitor, here pure white. Now take a broad brush and paint on the image with black: only the blue channel is affected and you see that the blue is taken away: black is brightness zero, so the blue has a brightness of zero.
What do you see? LBJ on LSD?
It's a kind of magic...

You can also duplicate a channel so as to safeguard your valuable information.
You can also open an new channel. Becasue the engineers had to give this a name, they called it an alpha channel. (with CMYK you also have spot channels, but I leave these out for now).
When you select this by clicking on its name, you can draw on it like on any greyscale image, use filters (clouds, crystallize, Gaussian Blur,...), use gradients,...
And what's so fascinating about it is that you can load this alpha greyscale image as a selection.
You know a selection is used to tell PS which pixels that you want to apply your changes on. And a mask is exactly the opposite: a mask tells PS which pixels you want to protect.

You can save an alpha channel (which contains a greyscale image of your making that is used as a mask) with your PSD file and re-use it later by loading it as a selection.

The big advantage is that you can actually see what happens when you draw or compose your mask: a selection is only visible because of the marching ants, and these only give you a faint idea of what is happening as they don't show all of the greyscale values.

Try this: open a full colour image in PS (RGB mode).
Go to the Channels palette and create a new channel. See that it is selected by clicking on the Alplha1 name. But keep the composite channel visible.
Apply a gradient from black to white, circular. to the Alpha.
See what it does.
Now with the Alpha still selected, open the Levels dialog and change the settings. See how it influences.

Click on the load as selection button and observe where the marching ants exactly are: they don't show your entire selection.
Now apply some effect, for example Invert (that's always a very good one for a demonstration.

Have fun.

When you understand this, really got it into your system by practise and experiment, all them so called difficult ones like layer masks (works in the same way) and and adjustment layers suddenly loose their power, like a ghost that loses its blanket.

Edit

Re-reading this, I found it clear as mud...so I added quick image which is posted further on in this thread.
 

theKeeper

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Hey thanks goes to OZ & Erik... i didn't contribute anything... just reaffirmed OZ's statements for you. ;)

PS: Try this Rick to help blend the animal model into the bg image a bit.

Dupe the bg image layer, and put it above the animal model's layer. Give the duped layer a 4-5 pixel Gaussian Blur. Then Mask out just the animal, by "Clipping" the duped bg layer to the animal model layer. Now set the blend mode to Softlight; and drop the opacity to 50% or so if it looks too strong.

This allows you to move the animal around the image, and have it assume some of the colour and lighting from the surrounding area in the bg image. The effect should be very subtle, and not particularily noticeable.
 

Tron

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Thanks Guys that really helps
Erik great info I can hardly wait for the next instalment.
One thing about PS and this board, you learn something new everyday :perfect:
 

Indigo

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I really like the background of this image, Rick. It looks like a scan of a picture and yet when I look at that green spiky plant next to the tiger it looks painted. Is there more going on here then just a scan? The tiger is quite convincing (his right back leg seems a tad too straight tho).
Please show the final image once you have blended in the tiger more into the background. Think you're up to something here!
 

Erik

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Here it is.

Open a white doc.
Write or draw on it with black. Result: black on white (what did you expect?)

BUT: Keep the eye icon on the composite (RGB) channel and activate (select) one by one the Red, Green and Blue channels and draw on them with black.

What happens for example to the Red channel? By painting with black, you specify that where you paint the brightness value for red is zero.

White is 255,255,255, but now you say that red is 0, so the colour you get is 0,255,255 (no red, full green and full blue).

ah, man, stop talking math![slick]
 

x-sniper

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ur right its yellow:)
any way u can do it the easy way just put the eye on for 2 colours say red and green, you get yellow...
simple.
 

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