How do you Post-Render colour correct the "cold, grey" images from LWF?

[Morne]

Hi all

Technically speaking this is not directly a vray question, but one that is still very related to rendering and espesially LWF so I decided to post in this section. There are lots of posts about LWF and how to set it up, but not much detail about how to get a correct final image after you save your render from VFB.

Just about all my images come out cold, grey, lack colour and that "extra ummph" the workflow is suppose to give me. Fine so far I'm getting it (according to threads I've read this is what you get from LWF). OK fine so how do you fix the colours afterwards in photoshop for stills and combustion/nuke for animations.

Trick1 (almost works but doesnt get me there
Can't remember who came up with this one but In photoshop go to curves and make an "s-curve". This curve is different for each image as your likes. This trick brightens my image and gives some colour, but makes some areas much darker and loose detail. But ok it sort of almost work for me.

Trick2 (also almost works but still doesnt get me there
Copy your image to a new layer and change the blend mode of the new layer to screen (and set opacity at desired level maybe 50%) This trick also almost gets me there, but not just yet.

Fool proof trick?
So what am I suppose to do in photoshop to colour correct my image and make it warmer and the colours come to life. Is there a fool proof way of doing things? one that works every time?

I'm sure I have the LWF thing down, but after that I'm unsure of what to do. Can somebody please tell me their workflow step by step after rendering asif I'm a complete idiot

[bardo]

I'm not a super colorcorrection expert but I think that it's more closer to an art than a science....so I thinkn there isn't a standard rule....

The 2 tricks you wrote are a good start...but only your eyes drive you to the best result.

[muoto]

i recently used the "lwf" option in the new SP3 render settings, and it works great. (I used all max settings at 1.0 gamma)
I had nice contrast, nice saturation !

[plastic_]

Those methods don't make sense...

If you want higher contrast you can always do it in post. But it's better to fix the values in the first place.

LWF just fixes wrong light distribution, especially excessive color bleeding. It does not affect the quality or the dynamic range.
I recommend to start from scratch with every scene, as with painting, it's all about the (diffuse) values. Converting old scenes to LWF doesn't work well.

[joconnell]

Bingo - If you want more contrast in real life you use more lights in closer to something - film negatives always come out rather flat and you grade them to taste after - The nice thing about lwf or gamma rendering is that you're getting so much information to play with after - you've lots of detail in the shadows and a nice even roll off from the lights so you've lots to play with in colour correction after.

[Morne]

Those methods don't make sense...

If you want higher contrast you can always do it in post. But it's better to fix the values in the first place.

LWF just fixes wrong light distribution, especially excessive color bleeding. It does not affect the quality or the dynamic range.
I recommend to start from scratch with every scene, as with painting, it's all about the (diffuse) values. Converting old scenes to LWF doesn't work well.

So what you saying is that I'm wrong in accepting the fact that all my stuff comes out cold and grey directly from VFB and I should look at making my diffuse warmer to start of with? Then I'm confused since all the fabrics etc I scan or take foto of the original and use it as textures, but when rendered it looks colder than the original jpg. What's up here? ligthing? underexposure?

Bingo - If you want more contrast in real life you use more lights in closer to something - film negatives always come out rather flat and you grade them to taste after - The nice thing about lwf or gamma rendering is that you're getting so much information to play with after - you've lots of detail in the shadows and a nice even roll off from the lights so you've lots to play with in colour correction after.

OK so the question was how do you guys usually colour correct stuff afterwards?

[simmsimaging]

Can't say that I agree with Marc's advice actually, although I agree with the sentiment that there is no single magic bullet for all renders.

You can increase the contrast of your lighting by things like moving lights in (or using smaller ones etc. etc.) but you can also increase your contrast a thousand other ways. If you want to increase your contrast without changing the quality of your light you can do it in post, or in the example someone gave of negative films you can push-process or polarize your lens, and on and on. There is no right or wrong about it - they each offer variations in look and workflow, but the end result is all that matters.

LWF does actually make a difference in dynamic range - it's the main reason I use it, so it's not just about distribution of light IMO. It gives you a full dynamic palette to play with in post. My approach is to get a solid range of shadow to highlight value in the .exr and then play in Photoshop. There's nothing "wrong" with that approach and it is often wildly faster than endlessly tweaking and render testing in Max, but to each his own (and I work in stills so that changes things too of course).

In any case, to the first question: there is no carved in stone approach because every lighting scenario and set of materials will mean a slight variation. It's just like photography - there's no one "treatment" I would use for any and all photos either.

The LWF renders do feel flat, and can often be a bit neutral (although that is more about your lighting than anything) so try a few things that work for you and then adapt from there on a case-by-case basis. I personally tend to render LWF and then in Photoshop I bump the gamma to .85 as a starting point to improve contrast, but it changes all the time too.

Anyway, the main thing is to get over the notion that you must have one approach - then you have all the options you need.

b

[JeffG2]

I punch the black level up a bit in the VrayFB.

[joconnell]

Generally just curves in after effects to get rid of the flatness - enough to add some contrast without pushing large areas of the image to solid black or white.

[stevesideas]

I generally get as close as possible, or as far as I can in 3dsmax and vray and render out the scene and then do the post work in photoshop, adjusting curves, colours etc to what I think works. I then try and re-match the post work using 3d studio max. I find it's easier to hit your target result, ie. enough contrast, correct exposure and warmth (depending on the scene). Also that way I learn quickly how to set up future lights, exposure, gamma and scenes. Obviously, that only happens when I have enough time to learn from my setups.

[duke2]

New adjustment layer->Gradient Map->OK->Soft Light mode, 60%->Double click it and make like this:



Problem (partially) solved.

[jujubee]

Trick1 (almost works but doesnt get me there
Can't remember who came up with this one but In photoshop go to curves and make an "s-curve". This curve is different for each image as your likes. This trick brightens my image and gives some colour, but makes some areas much darker and loose detail. But ok it sort of almost work for me.

That would have been Daforce.

[rajdarge]

to be honest I am a new convert to LWF. until I read this document - (it made it all clear) I thought it was a stupid waste of time and yielded washed out images:

http://www.aversis.be/tutorials/vray...l_gamma_01.htm

so I set up gamma and lut in max at 2.2 (I previously calibrated my screen): input gamma 2.2, output gamma 1.0. I then put 2.2 in the gamma of the "colour mapping" area. If I am using the max frame buffer rather than the vray frame buffer I think I change the output gamma to 2.2 as well. (havent used it in a while)

I also use "coolpicker" for colours as it forces you choose colours with the correct gamma applied

if I something is critical for colour then I use "vraycolor" map and chose a colour then it pre-applies gamma - I think this is the preferrable way for darker colours (for technical reasons that I read but cant remember).

so the frame buffer output loads in photoshop without washed out images and nice deep shadows. I don't have to change any of the gamma on the input textures and I don't tick the "LWF" button though I probably should read up about it.

Now I am pretty much a noob to max so you can choose to ignore what I say, and I would love for someone to correct me if I am doing something really dumb.

Raj

[duke2]

I don't have to change any of the gamma on the input textures and I don't tick the "LWF" button though I probably should read up about it.

Raj

The LWF button was added for old scenes so you had an almost 1-step solution. It's generally not used for any other purpose/new scenes.

[joconnell]

I kind of like the lwf button to be honest - it's really quick for simple scenes!