Why you use LWF? and how?

[m_hinks]

Hi peeps,

Im new to vray, but have spent a long time reading through this forum and have totally missed the point for using LWF, and also how you do it.

So two things really! Firstly, can someone sum up why you use LWF. I need to understand so I can tell me boss so we can start to use it. At the moment we use adobeRGB 1998. we have hardware calibrated monitors and work in a colour controlled environment. They only time we change the colour of the image is when it gets turned in to CMYK for the printers.

And secondly, if someone can finally produce a document explaining the benifets and how we set our machines to do LWF. There are so many methods mentioned, is there not one that is correct/better.

Tell me to go jump if you like! we'll continue to produce images straight out of max and apply adobeRGB in photoshop. When we get images printed they near always look how they look on our monitors!

Thanks

[jow]

Hey, Do a search for LWF, there are loads of threads covering it (infact to many!!)
There's also a video tutorial that someone on here put together.
Good luck, once you get the hang of it you wont look back

[m_hinks]

Yeah i really hope so, I just dont see the advantages yet.

To make it clear, I have read prob most of the threads on the subject. Thats is why I think someone needs to put together a master doc to cover the subject.

cheers

[panthon]

You can start here:

http://www.gijsdezwart.nl/tutorials.php

[Neilg]

It makes things brighter.

When you boil down to it, on its own thats about it.
Because the light is brighter within vray, the GI is supposed to be more accurate, but it can go either way depending on your skills and for talented artists this becomes irrelivant.


Its a lot easiar to get better looking materials with it, and its also better suited for interiors, theyre a lot easiar to light because of how it works. From what ive found, exteriors dont really benifit from it (apart from in the following
You can match colours to their real-world counterparts almost perfectly if you use the colour correct plugin, so if you do alot of interior design spec work you'll probably benifit.

Although saying all that, its awkward as hell to use without the colour correct plugin, which doesnt work in max 9, and its awkward as hell to use the colour correct plugin in the first place (every single colour swatch you plan to use needs one if you want them to be reliable, including reflection, refraction, opacity.. etc)

Give it a try and make your own mind up.

That being said, I really dont like the way its considered a be all and end all solution - use it when you need to, not because its 'better' - Its just different, like changing your colour mapping, only deeper and more elaborate.

[m_hinks]

Thanks panthon, that link was usful, ive printed it out to read now.

Now ive read it, and showed it to a couple of collegues, its starting to make sense!

It seems it doesnt matter what rgb/srgb you use, its all down to setting your monitor up correctly, we've done that. And now setting max up so it displays the render correctly on the 2.2 monitor.

Can someone stick up a screen grab of the preferences/gamma panel so we can see the sorrect settings.

Am i right in assuming theat once these settings are done, we dont have to colour correct any maps or colour swatches?

Thanks

[grasshopper]

Hi all,

m_hinks, Sorry for hijacking your post but I’m in a similar position as yourself so hopefully 1 post is better than 2.

I too am relatively new to Vray and have never considered colour or gamma correction until now. There seemed to be so many variables fixing it in post just seemed so much easier.

Having said that reading many posts and tying to understand the concept i am trying to set up a work flow and here it is so far so could someone please verify or destroy my results.

1. Calibrated monitor.
2. Colour Settings in Photoshop: Workspace RGB - Adobe RGB (199
3. Vray: Colour mapping - Gamma Correction - Inverse Gamma 0.4545
4. Colour Correction Plugin - Gamma 2.2
5.Save as 8bit tiffs open in photoshop.

Now as i say i'm new to this so there’s a few questions.

Am i correct in thinking i don't need to touch Viz's Gamma settings?

Whats/wheres the best place to apply the colour correction plug in? I only downloaded it today and at first glance i need to apply it to the diffuse channel of every material and set gamma to 2.2. Is this correct or is there a way to apply it globally?

Anyway think that’s enough for now any answers and comments would be gratefully appreciated.

Thanks in advance

[m_hinks]

np grasshopper.

Im thinking that if you have to use this colour correction plugin for every map and colour, we simply want use LWF. Its not worth the effort. I am hoping that you can set up max/viz gamma in preferences and it will effect all maps and colours there after. That would mean you could do one setup and then all is good.

But we need someone to clarify the exact process of how to use LWF.

[grasshopper]

What i can figure.

You need to use gamma correction to adjust for Vray being correct and monitor displays being guff. If you instead try and increase lighting levels to compensate for gamma your lighting becomes incorrect patches get blown out and rendering takes longer due to extra light calcs.

However when i apply the gamma correction the render looks washed out which is what i understand colour correction plugin is supposed to compensate for. Now i may be wrong and if so i'd really like to know.

I have been doing some quick tests this morning and found no difference between using Vray gamma correction & Viz gamma correction both look washed out unless I set material input gamma to 2.2 in which case everything appears over saturated. Material output gamma 2.2 seems to do nothing at all.

Could someone kind person please put us out our misery?

[joconnell]

Okay here we go:

A default crt monitor doesn't display colour in a linear fashion, it actually darkens the midtones of your images. When you use lwf, you apply a brightening curve to your images that is the exact opposite of your monitors darkening curve which cancels it out and restores your render to linear colour.

Textures and bitmaps on the other hand already take into account the monitor darkening when you scan or photograph them with a digital camera so they look correct on a monitor already. The problem is when you bring them into max, their already correct colour gets the brightening curve of lwf applied to them so it's like they've been brightened once on acquisition and a second time when you apply your gamma to the render, hence getting washed out. You can counteract this in two ways.

One is to use the colour correct map and apply a darkening curve with the same amount you're going to brighten it by later - it seems like a counter intuitive step that we're breaking our image only to correct it later, but you're just preparing for the fact that you're brightening the image later. The second way to do this is to tell max in your preferences to always apply the darkening gamma curve to every image that comes in so you don't have to manually use colour correct later.

As you correctly said, most people brighten their renders using a lot more light - the problem is that gamma affects the midtones mainly but not the highlights or shadow areas so your extra light that you pump in burns the highlights and crushes the shadows while not getting much effect in the middle area where you want it.

This make sense?

[grasshopper]

Yeah thanks a lot jo. Makes more sense now. a logical explination at last.

So if i'm using the Vray Frame Buffer and outputing to tiffs i should have.
Vray Gamma correction Gamma 2.2. OR invers 0.4545
Viz Gamma correction on with display gamma 2.2, material in 2.2 and material out 1.0

These settinging seem to get me a consistant

Viewport-->Render-->Photshop file

Thanks a lot & hope this helped you to m_hinks at last consistancy

[m_hinks]

yeah kind of, I think some screen grabs showing the various settings in use would really help.

[joconnell]

Yeah - one of the annoying things is that there's four or five different ways to use lwf so with options comes confusion. Your workflow is perfect - it might be better to render to a floating point image so you have a little more latitude in colour correction but if your renders are really close straight away it mightn't give you much benefit.

As regards the 2.2, that's assuming that your monitor is definitely calibrated to 2.2. If you don't know for sure, just pick a setting that looks right to you and make sure that you apply it consistently through your scene. If you had your monitor calibrated to 2.0, you'd be using gamma 2 or inverse 0.5 instead - personally here I don't have a monitor calibrator so I don't know for certain that 2.2 will give me accurate lwf - I just change the vray gamma setting in the colour mapping until it looks nice. 2.2 happens to be a good bet for crt monnitors There's been a few cases recently where I wanted more contrast from my renders which meant either doing that in colour correction or using a less washy gamma - 1.5 in that case.

It's the usual case of whatever looks good to you is the right value to go for but since most people want natural looking light in the first place, proper lwf seems to be a better option than anything else.

[joconnell]

yeah kind of, I think some screen grabs showing the various settings in use would really help.

I'll write something up.

[m_hinks]

That would be v cool. We have hardware calibrated monitors here, so I am sure 2.2 will be correct. I just need to know the simplest way to use a LWF without having to get everyone to start putting colour correction plugins everywhere.

Thanks again