Day for Night on Digital - 2 Stops under or 2 stops over?

[Marcus Friedlander]

Hey everyone,

I was reading about the VFX work done on Mad Max and I saw that they accomplished their Day for Night sequence by using the opposite technique to what is considered normal. Instead of under exposing 2 stops, they over exposed about 2 stops.

Shorter explanation (starts at about 1:45) - http://www.fxguide.com/quicktakes/mad-max-fury-roads-day-for-nights-and-practical-vfx/

Longer explanation - http://www.fxguide.com/featured/a-graphic-tale-the-visual-effects-of-mad-max-fury-road/


This seems like a more logical way to accomplish Day for Night with digital so why is 2 stops under still the standard? Has anyone tried this on DRAGON and gotten decent results? I'm going to go do a basic test right now. I'll post the results later today.

 

[David Mullen ASC]

Sort of depends on your highlight protection versus how much shadow detail you want to work with. You definitely don't want clipping in day-for-night shots.

 

[Marcus Friedlander]

So I finished testing and I found out that there is a lot more flexibility in R3D files then I realized! Unfortunately I am a terrible colorist but I tried to at least push the image in the right direction.

Link to dropbox folder with pictures - https://www.dropbox.com/sh/rsshsfwqouf7sd5/AAA8QiqHt9iEvl4yrHoGBSy4a?dl=0

TEST INFO:
CAMERA - Red Epic Dragon
LENS - Tokina 11-16 F2.8 EF Mount
ASPECT RATIO: 6k 2:1
REDCODE - 5:1
FOOTAGE WAS HEAVILY GRADED, BUT ALL CLIPS STARTED OUT WITH A BASIC DAY 4 NIGHT LOOK THAT I BUILT.
ALL STILLS WERE ADD'ED WITH THE SAME SETTINGS

MY FINDINGS
Clip 1 -
Iso - 12800
F stop - 23
Results - With a better colorist this is absolutely useable.

Clip 2 -
Iso - 500
F stop - 4
Results - Not even remotely useable. Not surprisingly, Mr. Mullen was absolutely correct about the clipping. If even one pixel is clipped the effect is pretty much ruined.

Clip 3 -
Iso - 500
F stop -14
Results - to my eye, this is the most convincing late dusk/early night look that I got.

Final thoughts - I didn't have any ND filters on me, so I couldn't really push the underexposure side of this test. However, after this test, I think that a very carefully planned overexposure will yield the best results. My last thoughts are that if I was a competent VFX artist, I would love to test out what would happen if you fully clipped the sky, and then replaced the whole thing. I have a feeling that a full sky replace is probably the least restrictive way to accomplish this task but I will need to test to confirm.

I would love to get everyone else's opinions on this subject!

 

[David Mullen ASC]

I think if you are worried about noise, then just expose normally, watching for clipping, and then darken in post. Even with film, I generally only underexposed DFN by one and a half stops, and keep in mind that I was rating the stock 2/3's of a stop slower than recommended, so my "true" underexposure was less than a full-stop -- in other words, I was doing most of the darkening in printing.

There is also a difference if you are going to be creating most of the effect in post with sky replacement, etc. versus just doing it in-camera where you want to avoid the sky or darken it with ND grads and Polas, often combined.

The other thing is to reduce the depth of field because true night photography tends to be at wider apertures, though "Mad Max" went for a fairly deep-focus look as often as possible, night or day, but it was going for a graphic novel comic book sort of effect.

I don't really understand why the vfx people wanted Seale to overexpose his DFN shots for "Mad Max" when normal daytime exposure would have worked fine, but they were certainly trusting the Alexa not to clip anything that wasn't going to be replaced in post. They might have been worried about blue channel noise, I don't know.

 

[Brett Harrison]

In the FXGuide podcast (starts around 34 minutes) (http://www.fxguide.com/fxpodcasts/fxpodcast-293-mad-max-fury-road/) the VFX supervisor explained that the idea came from his experience bracketing on set HDR environmental stills for image based lighting in CGI - he thought that the 'exposed to the right' (on the histogram) images in the bracketing sequence always came out better when you dropped the ISO in post, IOW you don't want to expose 'normally' if your 'overexposed' image - when blanaced out in post - doesn't have any unwanted clipping in it. And since the Alexa has such a powerful shoulder, it's quite rare to get it to clip. So I believe they shot some of Fury this way after they validated this philosophy.

Interesting conversation, worth listening to the whole podcast.