Artificial light intensity vs natural light

[fraggle]

Hello,
When working to an interior scene lighted from the windows by a (natural) HDRI (Dome or Env), the extra (artificial) light added to the scene have to be boost incredibly (like a 50w IES by 5000% or even more).

The relation between the HDRI (natural)/vray light (artificial)are not matching the reality at all. A 50W bulb 20 cm away from a wall, such wall under shadow, with a large open windows, even on a shinny day, will be visible on the wall, but not in vray.

On such scene, you start to play with incredible numbers and more light you have (IES, Vray IES, Plane, vraylightmatl...) and more difficult it is to have the lighting balance properly because we lost the roots of physical rules.
I didn't try yest but I guess a vray sun may raise the same problem.

Maybe a solution will be to lower the HDRI intensity around 0.01!

How are you guys dealing with that?

[flino2004]

whatever looks right.... since you are not trying to do a simulation.
you can start backward....put all the lights like is a night shot(at 100%), use your camera exposure to get the light that you want and turn on the dome invisible.... use a copy of your hdri for the background so you can control it independently

[Neilg]

I just change the intensity of the lights until they look good. .5 or 5,000, doesnt matter to me.

[fraggle]

thanks, we share the same approach. But then to get enough light out of the dome, you can't get it too low and them again you have to crank up all artificial light by a big amount.
But again, the main idea of using a physical cam, is to stick as much as possible to the physic, so at least there (from my point of view) the work is done with real ref from the real world.

whatever looks right.... since you are not trying to do a simulation.
you can start backward....put all the lights like is a night shot(at 100%), use your camera exposure to get the light that you want and turn on the dome invisible.... use a copy of your hdri for the background so you can control it independently

[flino2004]

usually I like to have diffuse light coming from the windows if I have artificial lights on. HDRIs are not physical accurate in my opinion, it's a representation of an specific hour of the day with multiple exposures but you still need to move gamma or intensity to looks like you want. the backplates that come with the HDRI help to calibrate them as well as the cameras. if you see professional pictures and you have a lot natural light coming in you rarely see the artificial lights (the cone) ... specially if it's white light.

[squintnic]

you just adjust the lights to a value that works
its not real life its a render

[Morne]

you just adjust the lights to a value that works
its not real life its a render

That depends and the end goal, I've had a number of jobs over the years where the client inisted in seeing what a shop will look like with a specific light fitting, from that they would know to add more lights or not...

[alexyork]

If you ever have to choose between using crazy unrealistic values for either your VrayLights or your HDRI, choose the HDRI. I would always keep my VrayLights to proper values. Makes managing things far simpler and the way the lights work with materials and the camera will be far more reliable and consistent.

[Neilg]

the way the lights work with materials and the camera will be far more reliable and consistent.

Doesn't make a bit of difference. If the light is twice as bright as the rest of the things in the scene it doesnt matter what numbers are in play to make it so.

[alexyork]

Doesn't make a bit of difference. If the light is twice as bright as the rest of the things in the scene it doesnt matter what numbers are in play to make it so.

But if you're trying to work with real kelvin temps and light power etc. then it's going to be a nightmare if they're all out of whack. It's far simpler to keep them all within real-world values then tweak your overall lighting and/or HDRI etc. to get the general levels correct. It also means that when you bring in other lights and models from your library which also have real-world values, they will work perfectly in the scene. In a typical interior scene with perhaps 10 different real lights and one HDRI, it's a lot quicker and simpler to play around with the HDRI and your camera/exposure than starting to fiddle with those 10 lights.

[Neilg]

How will it be a nightmare if they're out of whack? If it's too bright, drop the number, if it's too orange, raise the temp etc. everything else is irrelevant, it's just about as simple as it could possibly be.

[alexyork]

How will it be a nightmare if they're out of whack? If it's too bright, drop the number, if it's too orange, raise the temp etc. everything else is irrelevant, it's just about as simple as it could possibly be.

Because if you keep things in real-world values, or at least close, initially, then it's much easier to spot when something's looking wrong down the line. If all your lights are between 800 and 100000 watts and kelvin temps equivalent to 200 or 9000 then it's going to be harder to spot when there's an issue and much harder to balance things. Same with the temperatures. It's much easier to diagnose exposure and white balance issues if you keep things simple and realistic as a base. You can then obviously start moving things around to make it look good, but if you start from a base of unrealistic values it's more likely that you'll run into trouble later. This sort of workflow avoids those issues. Just my opinion on my own workflow.

[Neilg]

I still think it's easier to just look at the image and use my eyes to see if anything looks wrong. it's pretty easy to see if something is twice or half as bright as it should be.

[super gnu]

i am definitely in the "if it looks good" camp, but i wholeheartedly agree about starting from a realistic base being a timesaver.

if youve got everything cranked to unrealistic values, then try to do another view of the scene, suddenly you find it doesnt work..

example: interior with lights adjusted to look right, try camera outside, windows are unrealistically bright for a daylit scene. pain in the arse cos you need 2 light setups.

this is exactly the issue im dealing with now.


having said that, i suspect that using sun and sky, and physical values for lights, plus physical camera, will be the right balance - dont think for a second chaos would allow their physical system to be so out of whack.. its more likely the materials and exposure/burn are not physically correct or something.

[alexyork]

i am definitely in the "if it looks good" camp, but i wholeheartedly agree about starting from a realistic base being a timesaver.

if youve got everything cranked to unrealistic values, then try to do another view of the scene, suddenly you find it doesnt work..

example: interior with lights adjusted to look right, try camera outside, windows are unrealistically bright for a daylit scene. pain in the arse cos you need 2 light setups.

this is exactly the issue im dealing with now.


having said that, i suspect that using sun and sky, and physical values for lights, plus physical camera, will be the right balance - dont think for a second chaos would allow their physical system to be so out of whack.. its more likely the materials and exposure/burn are not physically correct or something.

Yep this is basically my approach. Ultimately it's all about whatever looks right, of course, but the way you get there is important because it can save a huge amount of head scratching and issues down the line when working with other assets, other people, other studios or just trying to diagnose issues with your scene. I just don't see any sense in beginning your scene with crazy values when you're trying to avoid issues. You will always minimise the chances of issues arising if you try to keep everything within real-world values. You can then start playing around with things once you have a good balance. A good example is neon light - it just never looks right with real world values. But if your surrounding scene is also chock full of crazy values then it's going to be super tricky to get the neon to work properly.