Author Topic: Adjustment To Curve  (Read 18448 times)

2015-11-16, 19:03:03

dubcat

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I've been playing around with this amazing PSD made by Edmon Amiraghyan.

But there were a few things about this PSD that bugged me.
- The gradient has a pixel aspect ratio of 2.34, not pixel perfect.
- The grid does not match the fine grid in Photoshop, this made it harder to recreate LUTs.

Here is the new version where these problems are fixed.
I want to thank Edmon Amiraghyan for sharing the original PSD. All credit goes to him.



This is how you change to the fine grid in Photoshop
Or you can hold down ALT and click in the curve editor.





Remember to resize the curve editor



Here is the PSD in action.





« Last Edit: 2015-11-18, 01:48:13 by dubcat »
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2015-11-17, 11:23:59
Reply #1

maru

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Sorry for the dumb question, but what practical use could there be for this? I understand this is a great aid for understanding "what is going on" with the image when using different adjustment layers. You mentioned creating LUTs - can you shed some more light?

2015-11-17, 19:12:32
Reply #2

dubcat

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Here's a little guide on how I'm using it.

A LUT could be made of a gazillion layer blends, a curve, maybe a little sprinkle of Channel Mixer. Or maybe it was made in DaVinci Resolve or Nuke.
But in the end, everything can be recreated with one single curve.
You are kinda stuck with what you get when you are using a LUT, but if you can recreate the LUT, there is no limit.

This is how I do it.

I'm using AI42 004 from Evermotion as an example image.



This is how it looks like with a LUT.
In this case I'm using "Valencia" from Instagram, because it has a nice RGB spread for this guide.



After applying the Valencia LUT to the PSD I posted, you get this curve.



I find it easier to just draw the curve with this tool.



Then I smooth the curve with this tool.



You end up with this.
Now you can add more points and fine tune it.



When I have done this to R G and B, it looks like this.



And here is the final result.
Of course the more time you spend on recreating the curve, the more accurate it will become.



When you are done with your modifications you can export it as a LUT again.
This way you can preview "the final result" in in Frame-buffer.


« Last Edit: 2015-11-18, 16:00:56 by dubcat »
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2015-11-18, 00:39:03
Reply #3

vkiuru

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Dubcat, you are sharing a great deal of really useful tips and interesting information, even though some of it is way too specialized or technically advanced for me to understand :) Thanks!

2015-11-18, 03:02:43
Reply #4

dubcat

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Thank you, glad you liked it :)

I did a fun experiment today.
There is a dirty technique for creating albedo textures from shitty diffuse textures. You duplicate the texture, invert it, change blend mode to "Soft Light" and boost the vibrance.
I have made a LUT that does all this for me, but I wanted to see if I could get the same result from one single curve adjustment, and guess what.



The curve is not perfect, so there are some differences. Like the LUT has some RGB splitting here and there. But I didn't want to spend more time on it.
The curve is set to "Luminosity" blend mode, since I didn't split the RGB values.
Like, who would have guessed that this curve = duplicate the texture, invert it, change blend mode to "Soft Light" and boost the vibrance.
« Last Edit: 2015-11-18, 03:44:57 by dubcat »
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2015-11-18, 10:42:31
Reply #5

lacilaci

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well.. you might want to take a look into "3D LUT creator" by oleg sharonov.

It's pretty powerfull tool, creating luts for use in PS or elswhere, which you could use directly in let's say VFB+ so... pretty much all post done while rendering.

btw. why would you ruin your renders with instagram filters?? :D

2015-11-18, 11:08:09
Reply #6

maru

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2015-11-18, 13:32:19
Reply #7

borisquezadaa

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I just want to thank you for sharing this knowledge with the comunity. I was not aware of this info and i have not seen elsewhere something similar.
Interesting concept LUT.
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2015-11-18, 15:19:05
Reply #8

dubcat

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btw. why would you ruin your renders with instagram filters?? :D
Heheheh, I was waiting for the Instagram comment :P
It was only to show the RGB spread, most real film emulation LUTs stay pretty close on the RGB level.

This is Kodak Gold 100



This is Agfacolor Futura 100



you might want to take a look into "3D LUT creator" by oleg sharonov.
I ran the trial earlier this year to test the Color Checker calibration part. Pretty powerful program.

Creating luts for use in PS or elswhere, which you could use directly in let's say VFB+ so... pretty much all post done while rendering.
The whole point of this thread is to
- "decompile" existent LUT files, and make the modifications you want.
- identify what a program does and recreate it
Then you can export it as a LUT again if you want to use it in VFB+.

I'm using ArionFX "Photographic" Preset (without the tone mapping part) as LUT in VFB+.
This is what "Photographic" does. I remade this curve and exported it as a LUT from Photoshop.
(I never save renders with LUTs enabled, only for preview)





This is how you export LUTs from Photoshop if anyone was wondering. I forgot to mention it in the guide, I'll add it now.


« Last Edit: 2015-11-18, 16:08:12 by dubcat »
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2015-11-18, 16:12:19
Reply #9

Juraj

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I am going to be shameless and ask you if you would be willing to share that LUT from Arion ? Seems like what the parameter white (to raise overall midtones brightness) and small toe to keep blacks would do if full filmic mapping was exposed.

Also, why not saving with LUT ?

I am also pretty interested what "Local" tone-mapping looks like in Curve. Or Clarity/Punch/etc.. parameter.
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2015-11-18, 17:43:47
Reply #10

dubcat

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I am going to be shameless and ask you if you would be willing to share that LUT
Here you go, I have included my Unreal 4 version too :)

Also, why not saving with LUT ?
I know you, guthrie and warwick like to do as much as possible in frame-buffer, nothing wrong with that. But I get chills just by thinking about burning stuff into my images, guess I'm just too used to linear.

I am also pretty interested what "Local" tone-mapping looks like in Curve. Or Clarity/Punch/etc.. parameter.
I actually did some tests yesterday, but tone-mapping is kinda tricky, we are talking about super whites and the curve is only 256. But here are the results.
These are with default "RandomControl camera" settings.



Clarity / Saturation / Vibrance etc is also tricky since the curve is black and white. I removed blue and green to make the curve red.
I used CameraRAW in Photoshop. When we go into the minus range, it starts to blur the pixels together.



If you got any specific stuff within certain programs, just give me a word and I'll check it out. I love to find out how stuff work under the hood.
« Last Edit: 2015-11-18, 18:06:16 by dubcat »
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2015-11-18, 17:53:42
Reply #11

Juraj

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Thank you much ! Also amazing research :- ).

Ah, expected the clarity to create perhaps even more smaller hills, but looks like this isn't so easily creatable manually. Local contrast is very interesting feature, there should be more easily adjustable controls to it.

The tonemappers are suprising, I don't really see much happening, expected something different :- ) Well interesting.

Does LUT get burned into linear .exr btw ?
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2015-11-18, 18:03:21
Reply #12

dubcat

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Does LUT get burned into linear .exr btw ?
I have no idea since I always disable it :p Can do a quick  test.

EDIT:
Looks like the LUT gets burned with gamma 1.0 and it will not look correct.



EDIT 2:
I have made a version that works with 32 bit. People can now burn those precious linear renders!

« Last Edit: 2015-11-19, 02:32:01 by dubcat »
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2015-11-19, 14:09:26
Reply #13

-Ben-Battler-

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Thank you for clarifying a lot of things which kept my brain busy the last days. Such information is gold to me!
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2015-11-25, 05:27:45
Reply #14

dubcat

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I made a 3dsmax version



The default Color Correction mode is acting like Photoshop Brightness/Contrast with Legacy ticked.




I ran a few tests just for fun














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