Reinhard and Exr

[Vividus]

Hello everyone,

I am trying to understand how to save to exr properly in order to keep the full power and range of color of the format by working in 32bits however I am facing a big issue with burn out areas

My usual way of working is rainhard multiplier 1 and I play with the burn value to avoid burn out areas such as sun light coming in trough the window but my understanding is that as soon as you modify the burn value you loose the full range of color so saving in exr will be useless as it will not keep 32bits color range anymore

is that true?

[Deflaminis]

1 = Full linear and 0 = Full Exponential, everything between is a blend of the two. Exponential color mapping will push the brights down to a level less than or equal to 1. So yes, it is true. You can preview what you might get in post in the Vray Frame Buffer "Show Corrections Control" in the exposure settings. Your highlight burn downward is like a poor man's Reinhard. At least, from what I understand.

Best,
AJ

[Vividus]

got it, thanks for the quick answer

[thanulee]

This is important if u composite ur beauty from passes. If not doesnt matter much.

In any case, keeping ur reinhardt around .85 to .9 helps render finish faster by sacrificing minor information. If u can be 1.0 is ideal (100% linear). Doesnt matter much though cause in post u can tonemap really easy and bring ur image down to its proper levels, even if its under or over exposed. If u feel safer, go with underexposure (renders faster too) and keep an eye in the shadow areas. To be honest, doesnt matter much cause its cg we re talking about and not real photography, u can compensate that by decreasing the noise thresh a bit.
In general, u dont have to render 32bit, 16 is fine, contains almost as much information as a 32bit one with half the size. In very specific scenarios 32 bit will make the difference. Many people will tell u otherwise, its up to u to test it.

Personally i almost never had to go more than 16, maybe in some low key shots that needed really heavy re lighting.

this will sort out all the issues for u : https://vimeo.com/ondemand/tonemap/127023473

[Neilg]

you're not loosing range in the exr - clamping does that. burn is squashing the upper range to soften it out. you can squash it so much that everything fits under 1.0, but keeping a little burn out and playing with the exr tends to work best. meet it somewhere in the middle.

[thanulee]

Btw guys, i was playing with some hdr skies recently in a shot and in order to keep things flowing smoothly without wasting tones of time in post, i had to go exponential. And the weird thing is, exponential gave me a bit different (better) result than reinhardt with value 0.0, which supposedly is the same thing.
I wonder if this is a bug, or exr related.

[Vividus]

Thank you guys for the info! a did some test last night however I wanted to ask you guys

if you modify your rainhard burn value below 1 let say 0.85 like thanulee said then you do not need exr anymore right? tiff will do the job in this case

if you guys work on 16 bits how do you achieve those nice glow and bloom effects in post that look so natural then?

btw thanks for the link thanulee I am definitely going to buy it right away

[thanulee]

U should definitely stick to the exr. Its the best format for compositing. Tiff is not real 16 bit. Contains less information than an exr 16 and its a big size file as well.
If u do not intend to composite a single png/jpeg is just fine for minor curves adjustments.

As for the glows, if u got 16 bit files in 32 bit projects ur glows are perfect PS anyways uses 32 bit for 16 bit images by default, nuke i think the same and AE is really easy to set it up with 2 clicks.

Ye give it a look it totally worth it, he explains everything and has some neat tricks in there for ae/ps/nuke

[Vividus]

In order to save hdd space, I should go exr 16bits but how do I save it from the vray frame buffer?

should I save it with default settings?

[thanulee]

yep just like that just default settings

[Vividus]

got it! thanks for the help