HDRI Lighting and White Balance

[Crazy Homeless Guy]

I have a question…

 

Are people in general using camera exposure and white balance with HDRI lighting?

 

I only bring this up because I mentioned in another thread that I am growing tired of camera exposure, and have started using it in fewer scenes. It then dawned on me that perhaps it should be a no-no in general for HDRI lighting, or at least white balance should be a no-no for HDRI lighting.

 

Hasn’t the HDRI map already been white point balanced to look proper? ….wouldn’t doing it again throw things off? Or is my conceptual understanding of this flawed?

[Tommy L]

Travis, has your avatar changed forever, or is this just a sneak look at your face as a Wednesday treat?

 

In what context are you using HDRI's? Have you reated them yourself, using a professional package, or just fooling around? Are you trying to achieve realism? Or are you just working out a reliable way of using HDRI in a predictable manner?

 

When I use HDRI's with Vray, it is usually for interior studio shots (products etc) and I always use camera exposure with neutral white balance (white) and 2.2 LWF. I find I get great results. Thats using HDRI's Ive made myself in the studio.

 

For externals, I use a couple of downloaded HDRI's (never made any external ones) and each time I use them differently. Studio shots tend to have a more regular look and they tend to have less color (usually high key lighting, deep midtones).

 

Externals are a lot looser and require more experimentation. But Ill usually use the above as a starting point and tweak from there.

 

http://ict.debevec.org/~debevec/

 

Paul Debevec tends to know the answers to all things HDRI.

[Crazy Homeless Guy]

Wow, that is quite a link. Lots of information there that will take a lot of time to sort through.

 

I have various HDRI's I use, but I do not use them frequently. So they are untreated by me, but presumably they are white point balanced by the person who took the photo. As I revisit my lighting more, I probably start to tweak them some. I am most interested in getting 1 or 2 of Peter Gruthrie's HDRI's and testing them. There was a thread a month ago talking about how they surpassed the quality of others available.

 

What I am interested in is providing a sophisticated, refined lighting solution that creates a striking composition for the project.

 

I really don't care if it is photo real or not, especially considering many photos that are striking often involve natural lighting occurrences which don't typically show up in rendering with prescribed daylight systems.

 

We tend to gravitate towards the idea of physical cameras in our renderings, but in reality the physical cameras are sophisticated tone mappers that are designed to compensate and bring back into view the overly powerful lights we just placed in our scene.

 

In other words, ....are we just creating the need for physical cameras in our scene?

 

In real life there is a need for them because the light is raw and rough. We are not god, and cannot control that, so we need exposure to compensate for it. Unless we are in a closed studio setup, then we are god.

 

I am in deliberation as to whether the "physical cameras" we use in our scenes are more or less KoolAid that we are drinking to convincing ourselves that this is correct because this is the way it is in real life. ....are we doing this at the cost of creativity in our lighting schemes? ...or does it allow us more creativity?

 

 

Striking lighting does not necessarily reflect real world lighting. Hollywood is constantly revising real world lighting through extra lights, and post work to get the effect they want. Studio lighting setups are very controlled conditions in order to get the look that is desired.

 

...but we tend to plop a physical sun and sky system in the scene and say that this is correct because this is the way the computer deems them to be in real life? I don't know, maybe I am making this all to hard.

 

I am quite far off the original question of whether people are using white balance or not on their HDRI, but to me it is all tied together. Are we getting tied up in the technical concept which in turn is controlling our final product?

[Crazy Homeless Guy]

Travis, has your avatar changed forever, or is this just a sneak look at your face as a Wednesday treat?

 

Hah.... Just testing out a more personalized profile to see how I like it. I have been using the Stiff Little Fingers album cover for years.

[Tommy L]

Hollywood is hell-bent on super-realism. It is so because it suspends disbelief in the experience of the movie. So realistic, believable effects are good, in the majority of cases. Check out Paul Debevec again, breaking down how lighting on digital actors is all HDRI driven and composited in light capture rigs (Google video Paul Debevec TED, he recently spoke at IIC). Its really interesting and demonstrates that we are not (ahem) light years behind hollywood in lighting protocols.

 

Ultimately, I think you just play with it and see what happens. I think artists that struggle with HDRI are ones that cannot self appraise a render. If you look at it and can tell its not what your trying to acheive, you must know 2 things: what is wrong and how to adjust it.

I never start off with settings that I think will be final. In fact I often start off with a lighting system I know will be too extreme, then dial back.

One system I havent tried yet is HDRI blends (this is useful in studio shots) where you put different lighting objects, be they sky captures or softbox/strobe captures then you can rotate them in world space in the material editor. HDRI on the fly, if you will.

[alias_marks]

I am in deliberation as to whether the "physical cameras" we use in our scenes are more or less KoolAid that we are drinking to convincing ourselves that this is correct because this is the way it is in real life. ....are we doing this at the cost of creativity in our lighting schemes? ...or does it allow us more creativity?

 

I have a little chip about this as well and really never understood the nature of why physical cameras & settings were important in our 3d scenes. I get that they will really help someone coming form a photography background but at the end of the day it's mimicking something that doesn't even really capture light all that dynamically to start with. To me the physical is just a little feature, that doesn't serve all that much purpose except for a translator for people who speak camera-ese.

 

So why bind our lighting to the restrictions of a real world camera constraints trying to light our scenes with iso's fstops and all that jazz?

 

I think the lighting tools we have in 3d/render engines are much more powerful and can lift the restrictions of a conventional camera. I want to capture light in all its glory in my render engine, then pick and choose what show how in photoshop/after effects/nuke/whatever. Who the really cares about a sunny 16 rule? I just want my lighting to look the way I want it with simple adjustments. The physical camera just complicates things.

 

My 2c

Edited August 18, 2010 by alias_marks

[Matt McDonald]

Kind of staying on the off topic portion of this conversation, I too have had some concerns lately about the whole "physical camera" thing. Mostly, I think that people tend to be overly eager to say "I have this physical daylight system, I've placed a physical camera & I'm using physical camera exposure and the resulting image is obviously 'real'" But obviously, that's not the case. The resulting images is still an interpretation. Often I find myself looking at renderings and thinking "maybe, maybe that is what a camera would get but that's not what I'd see".

 

I think its worse with Mental Ray renders because of how Mental Ray handles exposure, particularly because almost every tutorial you read tells you to use the mr photographic exposure control. Over the last few months I've been learning V-Ray and I really like how exposure is handled in V-Ray, its more sliders and curves and you kind of monkey with it until you get a look that you like. With MR, tweaking your exposure settings is such a pain in the ass that I think one tends to quickly consider it set and move on.

[Justin Hunt]

I have been playing (trying to use) Vray for the past couple of months, the one area that still confuses me is the combination of physical cameras and tone mapping. Which is more corect?

 

As for the mrPhotographic exposure, I find I can fine tune it with more control than I can with the vray physical cameras and tone mapping. I would like to have the ability to control different views with different settings ala vray.

 

At the end of the day it is largely a matter of achieving the look you want and not getting too tied up in breaking the laws of nature. Consider them but dont be bound by them.

 

jhv

[notamondayfan]

From what I understand, white balance is used to compensate for the light colour / tempature of the lights in your environment. So for example if your interior scene uses a lot of incandescent lights, you would set the white balance to a tempature of around 2700k (a orangy colour), where as an exterior lit with a sun and blue sky, then you would use a tempature of around 6000k (a blue colour). This helps avoid the light colour affecting your scene, and makes white materials look white.

Now for HDRs, to acheive a balanced white, you would have to desature your HDR and illiminate all colour, which is kind of backwards, as you would lose the GI colour and bounced light.

Sometimes it is useful to desaturate though, for interiors sometimes I use a HDR for highlights and reflections, so I dont need / want the colour affecting my scene.

 

You can ofcouse affect the hue / saturation of an image in post, but why not just do it in Vray with white balance?

 

Deano

[Crazy Homeless Guy]

Perhaps I posted this topic a little hastily. I understand the concepts of white balance and why they are used. I also appreciate the capabilities that HDR's/EXR's bring to digital production.

When I posted the topic I was curious as to what people were doing with HDR's considering they typically have already been white balanced once when the images were shot. I was curious if people were white balancing them again, and it sounds as if they are. Or they are at least modifying the color by desaturating them to acheive the color they want.

 

I am intrigued by this. I am in the process of questionging and adjusting my workflow. It has stopped making sense to me as to why we are placing lights in our scenes that 100 times brighter than what they need to be, and then adjusting them back down through exposure control to where we can see them.

 

The argument for doing it that way is that it simulates real life. That may be true, but I can produce nearly the same results by skipping that step, and simply using a less intense light. And in reality the less intense light method I am using gives me control over the entire color balance of the image.

I think we are loosing, or I am at least loosing a lot of the subtlties of lighting when I use the "realistic" sun and sky systems that come in the packages. I am starting to beleive that these packages are hindering creativity in an effort to produce something that is conceptually more accurate to what everday life would be. I say conceptually because the sun and sky system are to simple to really produce the natural variations that we get in everyday life.

 

Hence the use of high dynamic images, which start to bring back some of these variations, but are still far from perfect. And why would we want to crank these images 100 times brighter than what they need to be. It just does not make a whole lot of sense when I think about it. We basically create a probelm by making the light to bright, and then we solve the problem through extreme tone and color mapping of the rendering.

 

I poo-poo'd exposure in one post. I am not sure if it was this thread or another. But either way, I think I was a bit hasty on that. I think exposure in the terms of controlled tone and color mapping is highly useful. But I think it should be done on images that are visible wihtout any tone mapping, and then used to fine tune the image. I feel that this will give you far superior control over the entire image, and that is what I want, is superior control over all color and aspects of the image.

 

Now, ....what I am waiting for is someone to tell me that using a sun that is 100 times stronger than I need and then tuning it back to where I can see it provides other benefits such as ppuching light deeper into crevices. But as of now, I am not sure that this is the case.

[Crazy Homeless Guy]

I have been playing (trying to use) Vray for the past couple of months, the one area that still confuses me is the combination of physical cameras and tone mapping. Which is more corect?

 

As for the mrPhotographic exposure, I find I can fine tune it with more control than I can with the vray physical cameras and tone mapping. I would like to have the ability to control different views with different settings ala vray.

 

At the end of the day it is largely a matter of achieving the look you want and not getting too tied up in breaking the laws of nature. Consider them but dont be bound by them.

 

jhv

 

Funny, ....I find it the opposite. I can control Vray's tone mapping and exposure better than Mental Ray's. Typically for Vray, I get the image to where I want it either with or without exposure, and then I use the color mapper to bring the brights and darks to where I want them. I like to use Reinhard with the bright multiplier set to 0.7. In Vray, Reinhard is a combination of linear mapping and exponential mapping.

 

But yes, at the end of the day use whatever settings you need to get the look you want. I am just wondering if we are creating more work for ourselves with less control, or if these crazy bright lights are that much better?

 

At one point I did come across some lens shader for Mental Ray that dove deeper into Color and Tone mapping, but I can not find them now. I searched fairly extensively for them over the weekend. I wanted to test them out on a scene I was doing some lighting studies with.

Edited August 23, 2010 by Crazy Homeless Guy

[Tommy L]

Im of the opinion that the physical sun systems in place in mental ray and vray are there in response to consumer demand, competition from non-biased render engines and trickle down from Hollywood. They are what they are, an approximation of reality and in most cases, thats what we arch-vis guys aim for. If you do the reading on the VraySky research (mainly into 32bit color values assigned to different areas of the sky dependent on sun elevation) it makes sense. It is also designed to work really well in a LWF method. When software makes your life simpler, then its doing what its supposed to do.

That said, creative control in the hands of the artist is usually a question of evaluating all the tools inthe box and choosing the method that best suits the job at hand. I think your work-flow audit is a great indication of your creativity.

This is very interesting to me right now as Im doing a dusk shot and really struggling with the lighting. Im going to scratch LWF and daylight system and go back to my roots....

[Crazy Homeless Guy]

Hollywood is hell-bent on super-realism. It is so because it suspends disbelief in the experience of the movie. So realistic, believable effects are good, in the majority of cases. Check out Paul Debevec again, breaking down how lighting on digital actors is all HDRI driven and composited in light capture rigs (Google video Paul Debevec TED, he recently spoke at IIC). Its really interesting and demonstrates that we are not (ahem) light years behind hollywood in lighting protocols.

 

Ultimately, I think you just play with it and see what happens. I think artists that struggle with HDRI are ones that cannot self appraise a render. If you look at it and can tell its not what your trying to acheive, you must know 2 things: what is wrong and how to adjust it.

I never start off with settings that I think will be final. In fact I often start off with a lighting system I know will be too extreme, then dial back.

One system I havent tried yet is HDRI blends (this is useful in studio shots) where you put different lighting objects, be they sky captures or softbox/strobe captures then you can rotate them in world space in the material editor. HDRI on the fly, if you will.

 

I watched the TED one, and it was interesting. Actually, almost scary in seeing what can be achieved.

 

I am having trouble downloading the others, they keep timing out. I think it has something to do with my connection here in our office. It gets finnicky like that when downloading from some websites.

 

I agree that HDR's are very powerful, and can provide a lot. But I would still question as to whether Hollywood is using something like the a sun and sky system, where they are placing lights that 100 times brighter than they need to be, and then tuning them back. I would guess that they are using a more refined and controlled method of lighting through things like HDR's and then using tone and color mapping to achieve the realism.

[Crazy Homeless Guy]

This is very interesting to me right now as Im doing a dusk shot and really struggling with the lighting. Im going to scratch LWF and daylight system and go back to my roots....

 

I agree with going with your roots on this. Whenever I try to use the Sun and Sky systems on a dusk shot I always struggle. The colors warp greatly into heavy oranges and yellows when the sun gets close to the horizon. Perhaps I am not controlling the white balance properly at this point to bring them back to where they need to be.

[BrianKitts]

Personally I never use an HDR for lighting a scene with the intention for going photo realistic. 99% of the time I can say that it's to achieve a mood or style to the image tones. The white balance comes in play when I'm partially happy with what I get out of the HDR and want to bend the color tones a bit to my liking. But it has to be said that when I use the white balance with an HDR it is not with the intention of hitting a perfect white in the render if anything it's the opposite to push the image into a different spectrum. So for that purpose the white balance feature of the physical camera is a nice feature to have, but I could do without it as it could be done in the workflow at post.

 

To answer the exposure question I still use exposure on my exteriors, specifically when I'm using the physcial sun, but the majority of my interiors now I'm not using the exposure at all. Actually the only reason that I use the vray cameras on my interiors instead of just dropping a standard camera in is because I like the ease of the vertical perspective correction in the vray camera options as opposed how max's camera correction is added as a modifier. And that leads into my final thought....

 

I found it interesting that this thread limits analysis and basis for using the physical camera solely on white balance and exposure. To answer the original question those are the two features that I use the least out of the physical camera. My reasoning for using the physical camera is 1. the previously mentioned ease of vertical correction all in one options panel, 2. (biggest reason) is I know how much motion blur I'm putting into my images for animation based on the shutter speed of the physical camera. and 3. Control of DOF when I do use it.... which isn't often but nice to have it setup with a direct relation to real world photography settings.

Edited August 23, 2010 by BrianKitts

[Tommy L]

I posted an image with this thread in mind here: http://forums.cgarchitect.com/61944-dusk-scene.html

[kippu]

i also agree , scratch LWF and get back to the old methods , that was far more interesting and easier to control to get exactly what we want , thanks for this thread ,