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Adjusting black and white point - how

Posted: Mon Jun 15, 2015 9:23 am
by gordonrobb
I'm trying to adjust existing texture (images) for use in Octane. I'm using the plugin, but it uses the same nodes so I'm posting the question here.

The ColorCorrect node used to have a black point adjustment but now it doesn't

What I want is what OTOY are suggesting is the process for adjusting black point and white point. I don't want to adjust the gamma (which I know how to do). I've found a few different work-arounds that each do something, but each do it differently.

What I'd like is what OTOY are saying is the way to do the following.

Make the blacks less black
Make the whites less white
Control where, from 0%-100% your images constrains it's black/white. So I have an image that goes frm 0% to 100% just now, but I want it to go from 10%-90% (without cutting off what is currently between 0-10 and 90-100.

Help!

Re: Adjusting black and white point - how

Posted: Mon Jun 15, 2015 9:47 am
by BorisGoreta
You have to mix the texture with the white RGB value to adjust the black point, and white point is adjusted using the power in the texture image node. So you don't need color correction node at all.

Capture.JPG

Re: Adjusting black and white point - how

Posted: Mon Jun 15, 2015 2:45 pm
by gordonrobb
I'll need it for contrast adjustment, but I can just feed your solution into it. Thanks, I'll give that a try.

Re: Adjusting black and white point - how

Posted: Mon Jun 15, 2015 3:01 pm
by BorisGoreta
There is a contrast adjuster in the Color correction node plus with gamma you can adjust contrast too.

Re: Adjusting black and white point - how

Posted: Mon Jun 15, 2015 5:22 pm
by gordonrobb
BorisGoreta wrote:There is a contrast adjuster in the Color correction node plus with gamma you can adjust contrast too.
yeh, that's what I meant, i'd need to use the colorcorrection node for contrast. It was in response to you saying I wouldn't need to CC node :

Anyway, tried your solution and it works a treat, except for this bloody gamma difference problem with Lightwave.

This is the original....
Normal.png
this is it in Photoshop with the black point adjusted to 128 (50% grey)
128.jpg
this is it in LW with the adjustment to 50% (with your node setup)
50.jpg
To get it similar, I've had to adjust it to 12%
12.jpg
This is ok, but the adjustments I'll lactaully be making with be darker than this, and 1% is a lot at the bottom end in LW>

Re: Adjusting black and white point - how

Posted: Mon Jun 15, 2015 5:28 pm
by gordonrobb
That's weird. My 128 image looks darker once I've posted it.

Re: Adjusting black and white point - how

Posted: Mon Jun 15, 2015 5:29 pm
by gordonrobb
Replaced it with a JPeg and that works