Alpha channel how to make them ?

[tuomok]

As always, it depends...

In alpha channel, white represents opaque and black transparent. And all the grey tones are somewhere in between.

Say if you have a photo of dark sky with a bright moon, you can quite easily use a greyscale version of the image (copy&paste) as an alpha channel. And by increasing contrast it'll probably work better.

But if you have say a photo of a forest and you'd like to isolate just one of the trees, you can for example create a new layer and start painting the areas to cover just that one specific tree and finally convert that layer to be your alpha.

Notice that if you have blurred edges (or otherwise grey areas) in your alpha channel, the final composite in those areas will be a blend of original photo and the background color of the application it is being used in.

Hope this helps.

[robin]

Thanks Tuomok, the help is appreciated im no photoshop expert

What im trying to say is that can i take a color image like this one (color) and make a new one (grayscale) out of it (this way i dont have to manually paint all that). Will this be enough when i put that under the alpha channel tab in photoshop or is there something that i must do to make portion of the B&W picture more white and others more black, all of this for my alpha channel.

In other words, by making my image B&W will this be a good alpha channel?


thanks

[tuomok]

It's quite hard to tell... I'd need to know where you will be using the final image, in 3D software, print, video compositing...?

See, in your greyscale image the veins are the darkest bits, so they will be transparent and the other flesh kinda surface will be visible. Is this the way it should go? Or the other way around...? In that case you need to invert the greyscale image (alpha).

[robin]

Its a texture for 3dsmax, i will use it over a cylindrical geometry.

If i invert the image it will give me this. Now how can i make the whites part whiter and the black parts darker ?

[tuomok]

Press Ctr+L (Adjust > Levels) and drag the handles towards the center.

[robin]

Damn Thanks tuomok, your my hero tonight.

I guess this should be more than enough to make an Alpha, im going to experiment on them like this. I wonder if by this method i still have 56 channels like ordinary alpha or if there's even a difference with a painted alpha.

Thanks again tuomok you've enlightened my path.

-R.


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