Vray night scene & photographically correct exposure

[eidam655]

Hi all,

 

I'm currently trying to make a night render using 3dsmax & V-Ray.

 

During the daylight scene i got used to using the Sunny 16 rule to set my exposures (f 16, ISO 200, shutter 1/200). However when I want to render a night scene, I can't use 'real' exposure values (like f 5.6, ISO 400, shutter 1/25) because the building interiors get overexposed, however low i set the vrayHDRI multipliers.

 

For lighting i'm using a vrayHDRI mapped onto vray dome light and have it mapped in GI and Environment slots.

 

How do you do night/dusk scenes using vray and 3dsmax? Is it possible to use real photoexposure values, or do you just fake it as long as it looks good?

[Devin Johnston]

There is no correct way to do night renderings or day for that matter, it's all about what you think looks good. You say that the interiors are overexposed and that your using an HDRI to light them, it would be helpful to see what your talking about.

[eidam655]

I apologize, I found out that i had Hidden Lights turned on in Global switches, and that was causing the strange lighting...

 

But not to rob you from the screenshots, here they are. I still have to put lights into the rooms, of course, but I wanted to test the exposure at this stage. Also, I'm using #10 from the VizPeople HDRi pack.

 

- all HDRi multipliers at 1.0, exposure not corresponding to real world situation

 

- all HDRi multipliers at 1.0, exposure adjusted to real values

 

- real exposure, modified HDRi Render multiplier

Edited May 20, 2014 by eidam655

[Morne Erasmus]

Devin is correct in the sense that its just a 3D, do whatever it takes to make it look good.

 

On the other hand, like you had good success with your day scenes by using "correct realistic" exposure, you can also get that with night scenes using typical real life exposures. Your camera will be "correct" and your HDRI will be "correct". If you're getting overexposed (or underexposed) interiors, the hint is in the settings for the interior lights. They should also have some kind of real life values, otherwise you're just chasing your own tail so to speak

[RyderSK]

Is the VrayDomeLight multiplier also at 1.0 ? By default it is created with value 30.

 

Also, if you're using DomeLight, what is the reason for mapping it in Vray override slots in this case ?

 

How did you decide what is the correct physical camera exposure settings for each HDRi ? VizPeople don't provide matched tone-mapped backplate.

[eidam655]

Juraj: Yes, I reset the multiplier to 1.0. The reason for the override was that I didn't know where exactly should the VrayHDRi be, so I put it in every slot that seemed to have something in common with the environment or the background

 

Morne: Yes, that's what I was aiming for, trying to use 'typical' exposure values.

 

For the exposure I took an 'educated guess' from Chart B in this article and the one above it - I went with EV 5 scenario, chose ISO 400 and that yielded shutter speed 1/4s at f 5.6. After that I adjusted the VrayHDRi Render multiplier and interior light intensity so that the image wouldn't get overexposed.

 

So as far as the workflow goes, I'm quite happy with what I discovered and will be using similar process for my future night renders.

 

And as the result I ended up with the attached image. It took about 1h20min at 5400x3000 and another 5 minutes to do _very_ basic photoshopping...

 

 

[guenther Malek]

you have to fake it; try to take a nighttime exterior photograph: interiors are always WAY overexposed...

[Ernest Burden III]

you have to fake it; try to take a nighttime exterior photograph: interiors are always WAY overexposed...

 

Exactly. Photoshop is your friend.

 

With the context images--I suggest re-painting the light rather than just darkening a daytime shot. (You may be planning to do this already). Put a softlight layer over it and lay in lighting at a low strength, building up to what you like.

[ganeshk]

Is it overexposed then you can also do Post Production to it. in Photoshop or After Effects. or Let the Lighting Multiplier Dicrease. I think then you can have the correct result with the correct way of using Exposure. and in Every Render try to use Post Production. Thanks