|07 July 2009||#1|
VFX | Film Maker | Musician
Hedon, United Kingdom
Join Date: Feb 2003
Lighting for Night-vision?
I'm in the process of pre production for a feature film.
Some of the footage will be shot using a camcorder with Night-vision and will require digital characters adding.
Am i correct in thinking i would only need to light using one light to simulate the cameras infared light (or whatever it is)
Should i light with white light and grade to green in post?
Also, should i use global illumination? I was thinking since it's going to be dark i'd get away with not using global illumination but i dunno.
Anyone done this before? Any advice/suggestions?
|07 July 2009||#2|
Join Date: May 2009
That depends a lot on the nightvision "feel" you get from the camcorder.
First of all i would do everything in greyscale, that way i could color correct the cg to match the hue and levels that you get from the camera.
I've seen several kinds of nightvision, but i'm under the impresion that the cameras got some kind of infrared light mounted on top of them, so i would link a spotlight to the cg camera, without shadow casting enabled, and i would also link an area light to the cg camera, with shadow casting, but excluding ilumination (I've never seen nightvision shadows with hard edges).
If i were doing it with 3Ds Max with mental ray, i would use, the spot linked to the camera, casting no shadows, a skylight with a dark pure gray (saturation 0, value 0.3) sky color, ambient occlusion with low samples (8) and very low distance (10 cm), and Final Gather with 1 bounce.
Then I would render at least three passes, one in 32 bit for the specular + diffuse + textures + Ambient Occlusion (and if you can, break this one into 4 passes), another one in 16 bit for the shadows, and a z depth pass, so it could be used as a mask for depth of field, color correction, etc...
I think that the Z-depth pass is essential to control brightness, because i think it is really hard to match the decay of the infrared light mounted on the camcorder (things closer to the camera are way overexposed, and stuff further away decay rapidly but almost never get to pure black, unless shooting the sky).
The first pass should be in 32 bit because it will recieve a lot of tweaking in post production, and the second one would only need to be in 16 bit because it will only get it's blending and transparency changed to match the camcorder footage.
Also, if i remember correctly nightvision tends to be noisy, so i would take a dark spot from the camcorder footage and try to reproduce the noise in post, so it can be added on top of the cg characters, and then, once composited i would add another layer of very subtle noise on top of all.
"Also, should i use global illumination? I was thinking since it's going to be dark i'd get away with not using global illumination but i dunno."
Besides being dark, the very alien lighting conditions, and the fact that everything is the same color, i would not do it.
If the camcorder allows you to capture stills, you could try to create IBL with nightvision, and then tell us how it goes
Last edited by Trauco : 07 July 2009 at 08:57 PM.
|07 July 2009||#4|
Los Angeles, USA
Join Date: Nov 2004
Notice the color ramp in this one: black > green > yellow > white
You could do that by rendering in black > gray > white and ramp / gradient mapping, but I just wanted to mention the non-green color in this one.
Also - human eyes may have big pupils, since to the human, it's very dark out. Animal eyes may have that silver version of red-eye. Have to investigate and see if you want either of those effects.
|08 August 2009||#6|
Join Date: Sep 2003
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