ALA - Another LWF Alternative - Thoughts

[johnvid]

After spending a lot of time with LWF, trying to get good results & and wondering if LWF was just another way to disrupt the workflow. I have just had an alternative idea...

 

Instead of reducing all the materials RGB Values to 0.255, I just tried reducing the main direct light power to 0.255, and the GI skylight multiplier to 0.255, so changing 2 values instead of hundreds.

 

Turned on the srgb, in the vfb, altered the exposure +1 stop, and tweaked the curves and Hey Presto the results looked ok, It was a real simple scene, so cant be too sure if its exactly the same results as the long drawn-out LWF method.. I can be damned if I am going to convert the scenes rgb values back to 1.0 without an automated script to test it out on a complex scene.

 

But in theory lights with such a low power as 0.255 should render quicker than lights with power set at 1.0.

 

Can anyone else out there test this on thier standard setup files and post results & opinions

Cheers

[AJLynn]

No, that wouldn't give you the same effect as linear workflow. Try instead the methods discussed in this thread - it's a lot to get your head around, but it's a few settings and you're done, and it does work.

[johnvid]

Sure is a long thread, more about working with gamma 1.8, and not too much of a difference between 2.2 or the results I have seen so far with the different image output formats...Resulting in images that still need tweeking in Post.

 

The method above did seem to work for me, the only thing I noticed was it seemed to give more colour bleed than I have experienced with my other attempt at the LWF.

[AJLynn]

Right. Because it's not actually linearizing the system, so it's retaining the same problems that LWF solves - this is why LWF is complicated, it's taking several different factors that are out of whack in Max and bringing them into whack. There's no really good one-click answer to this. Heck, it's really hard to even get a good explanation and too few people even really understand it (and I'm not one of them).

 

The problem is that Max's problem is non-linear. You look at your monitor and it's in gamma 1.8 or 2.2. Images you have saved on your PC are in gamma 1.8 or 2.2. Max is in gamma 1.0. This is a non-linear problem - gamma affect midtones but not the values of white or black, so it can't be solved by adjusting the light. The only way to do it is to make your gamma space consistent.

 

That .255 thing is one method that somebody figured out empirically, and for many scenarios it does work, but it's a lot of extra work for you. The way I do it, which works in mental ray and probably in Vray, is just to set up the gamma correction in Max. See attached image. I save EXR output which ends up having the right gamma, but if I were using 8 or 16 bit output I'd also set the Output Gamma. 1.8 or 2.2 is a matter of some discussion, I'm in 1.8 by habit but 2.2 is probably correct and I'll probably change it at some point.

[johnvid]

Hi Andrew,

 

Thanks for the info, your gamma in the attached picture is slightly different to how iunderstood it so far, the gamma setting on the left with the squares I have always left at 1.0, only changing the 2 on the left...I thought that was how it was recomended by most?

 

But my monitor which I believed to be 2.2 as it was an LCD LG L226WT, has a gamma profile, which comes with it but photoshop says its damaged. The monitor is very bright compared to my other monitor thats why i thought 2.2,

 

But in the ATI catalyst control center the Gamma is actually set at 1.0,(if i set it to 2.2 it looks far too bright and horrible to work with) which i believed to be linear because the line was straight...

 

In the Vray frame buffer you have curves and an srgb button, Ive read that you dont really need to set the output gamma to 2.2, especially with EXR's as you can do it all in PS, (but also read that the reason you can do it in the Vray Frame Buffer is for those people who dont have photoshop or other HDRI image progs.

 

If I dont set the srgb in the Vray frame buffer, I can almost get a similar image just by using the curves and the exposure settings...

 

Which is where i came in with the start of this topic, My results where similar without setting the rgb output of each material and also without replacing the colour swatch with a vray colour. (but I assume thats why I got the extra colour bleed).

 

Meanwhile I remember that before trying the LWF, I was getting good results from the standard max camera, while the physcam would be way out, even though I know all about fstops, shutter speeds, inverse square laws and reciprocity.

 

I am not really sure at the moment that i am getting any better results than when it was all set at 1.0, which is how i have worked for the last 15 or so years with a lot of repro work, my gamma was always set at 1.0, Then I have a friend telling me that adobe 1998 contains more colours than srgb, but this could be his misunderstanding, as the CURVE shouldn't really affect the amount of colour info, merely the way its presented, but he feels it is clipped to around 220 in the rgb channels???. but as you say it doesnt effect black or white

 

Then you read people saying the LWF is best for interiors, I was trying it on an exterior.

 

The only thing I think I may have achieved is shorter render times. which is why I think this method may give shorter render times also.

 

It sure is a MIND FLUX...