Over expose vs under expose for low Key lighting on a mysterium sensor

[Marcus Friedlander]

Hey everyone!

I had an interesting experience yesterday that I would like to share with and ask for your opinions. I dp'ed two small shoots back to back that were similiar styles but shot totally differently, the first was during the day in a studio with a very controlled lighting set-up and we were shooting a teenage girl dancing in a studio while another girl played piano, and the second was late that night and it was a super low key lighting rap music video. We shot on the same EPIC Mysterium sensor for both shoots but with two different directors who both wanted a low key lighting style. However, the first director wanted to spend time coloring the footage and the second director did not have the time to color the footage. I only had time to check out a couple of clips before they got shipped out to the respective editors and I probably wont see them again until this weekend so I cant share any of the footage for a bit, but I wanted to pick the collective REDUSER brain for opinions and critiques.

So for the first shoot I ETTR'ed about a half stop so they could have the room in post to work. The image was very bright but I felt like I lost too much of my lighting contrast at times. We spent a good amount of time defining the space with both the set design and the lighting but I feel like ETTR'ing might have hurt? Would the answer be bigger units to replace everything we had? Or will that lighting contrast get recovered in post? I was happy with the few performance clips that I saw but no so much with the lighting for the interview and close ups. But for the second shoot, since the director wanted to do absolutely no color correcting, I had to expose everything to the left to get our low key look. For pretty much every set up, every time I checked my false colors and goal posts they were screaming in the wrong direction. We usually had full purple except for the specific lighting we had for the shot. I was really nervous because I felt like everything was underexposed at least a half stop and usually more, but but the directer kept assuring me that the sensor would pull it off, so we kept going in that style. And the weird thing is that director was completely right. I only saw a couple of clips of that as well but whenever the talent fell into the light we got a really gorgeous exposure. While not all of the take was useable, most of it still was and for a rap music video there was more then enough to pull out and cut together a proper video.

So the next time a low key lighting challenge comes up? Should I keep ETTR'ing or should I trust the sensor and shoot for exactly I want?

Thanks in advanced for all of the help and when I get a chance I will post screengrabs or R3D's if I'm lucky :laugh:

 

[Blair S. Paulsen]

Since your impression of the results of the different lighting/exposure schemes was likely based on a rec 709 RC3/RG3 image at whatever ISO the camera was set at, I'd be wary of drawing conclusions from that alone.

FWIW I typically get the best results in shots intended to look low key by using an ETTR bias (more lighting if you need a deeper stop), resetting ISO in RCX-P (or Scratch/Resolve/etc) to find a natural looking middle grey point and then carefully crafting the toe of the curve to manage contrast in the shadows. The toughest part of shooting a bit hot to keep clear of the noise floor is that it affects the mood on set - it just feels wrong, to the point that it can affect performance with all but the most skilled talent.

Cheers - #19

 

[David Mullen ASC]

It's just like with shooting film, you split the difference, you don't underexpose as far as you want, you go halfway there and then print down to taste in post. I certainly wouldn't expose a very dark scene very brightly and then try to crush it way down, but on the other hand, I try not to underexpose quite as dark as what I think the final result should be because I want some timing flexibility.

But in terms of noise, you aren't really "underexposing" the shot by exposing it correctly for the look you want. In other words, let's say you test and find that the noise in the mid tones and shadows looks good to you at 500 ASA -- if you were shooting a well-lit scene at 500 ASA and the noise looked fine and suddenly the character turns off the lights in the room, or the AC puts the lens cap on the camera, does the noise increase just because the shot became several, if not dozens, of stops darker? No, because you aren't going to lift that dark shot back up to normal in post color-correction. If dark areas in the well-lit scene at 500 ASA, like a black jacket or shadow under a desk, don't have heavy noise in them, they aren't going to have more noise just because that dark area fills more of the frame -- after all, if a character in a black jacket walked forward until their black jacket covered the lens, would you continuously open up the f-stop in order to Expose to the Right? If you didn't, would the noise increase as the character in black walked closer and closer to the lens? No.

This points out the problem with following rules like ETTR blindly without thinking things through.

You test ASA settings to find a noise level in the shadows that you like or can live with. You then expose the scene within that rating for the look you want. But just in case the degree of creative over or underexposure will be tweaked in post, you be a little conservative with the exposing. But that doesn't mean you have to expose a moonlit scene like it was daylight, it means that if 2-stops under looks correct, then perhaps you only underexpose by 1-stop and then darken in post by another stop.

 

[Marcus Friedlander]

Since your impression of the results of the different lighting/exposure schemes was likely based on a rec 709 RC3/RG3 image at whatever ISO the camera was set at, I'd be wary of drawing conclusions from that alone.

Cheers - #19

I understand what you're saying in context of the first video that will be colored, but for the second video isn't what I saw on that computer screen what we got?

and then carefully crafting the toe of the curve to manage contrast in the shadows.
Cheers - #19

Can you explain this in more detail please, specifically what you mean by contrast in the shadows?

The toughest part of shooting a bit hot to keep clear of the noise floor is that it affects the mood on set - it just feels wrong, to the point that it can affect performance with all but the most skilled talent.

Cheers - #19

This was something that I was thinking about as well. We would all like to get the most perfect exposure possible but if the performance suffers as a result is it really worth it? Luckily it wasn't an issue for the girl dancing but it is definitely something to consider the next time this challenge comes up.

 

[Marcus Friedlander]

It's just like with shooting film, you split the difference, you don't underexpose as far as you want, you go halfway there and then print down to taste in post. I certainly wouldn't expose a very dark scene very brightly and then try to crush it way down, but on the other hand, I try not to underexpose quite as dark as what I think the final result should be because I want some timing flexibility.

But in terms of noise, you aren't really "underexposing" the shot by exposing it correctly for the look you want. In other words, let's say you test and find that the noise in the mid tones and shadows looks good to you at 500 ASA -- if you were shooting a well-lit scene at 500 ASA and the noise looked fine and suddenly the character turns off the lights in the room, or the AC puts the lens cap on the camera, does the noise increase just because the shot became several, if no dozens, of stops darker? No, because you aren't going to lift that dark shot back up to normal in post color-correction. If dark areas in the well-lit scene at 500 ASA, like a black jacket or shadow under a desk, don't have heavy noise in them, they aren't going to have more noise just because that dark area fills more of the frame -- after all, if a character in a black jacket walked forward until their black jacket covered the lens, would you continuously open up the f-stop in order to Expose to the Right? If you didn't, would the noise increase as the character in black walked closer and closer to the lens? No.

This points out the problem with following rules like ETTR blindly without thinking things through.

You test ASA settings to find a noise level in the shadows that you like or can live with. You then expose the scene within that rating for the look you want. But just in case the degree of creative over or underexposure will be tweaked in post, you be a little conservative with the exposing. But that doesn't mean you have to expose a moonlit scene like it was daylight, it means that if 2-stops under looks correct, then perhaps you only underexpose by 1-stop and then darken in post by another stop.

Wow thats a really interesting way to look at it, thank you very much sir! So if you've found the asa noise floor you are comfortable with, then it doesn't really matter where the histogram is as long as the blacks are clean and the sections you want to be lit are exposed properly? Then, after that its just about giving you a little bit of wiggle room in post by playing it on the conservative right?

 

[Marcus Friedlander]

Thank you both for your responses! Very informative!

 

[David Mullen ASC]

Wow thats a really interesting way to look at it, thank you very much sir! So if you've found the asa noise floor you are comfortable with, then it doesn't really matter where the histogram is as long as the blacks are clean and the sections you want to be lit are exposed properly? Then, after that its just about giving you a little bit of wiggle room in post by playing it on the conservative right?

Yes, but this is all contingent on you not trying to change your mind and brighten a dark scene too far.

On the other hand, it's very hard to create art if all you do is cover your a--- by making everything middle-of-the-road and giving yourself endless options to change your mind in post. What I'm suggesting is a reasonable compromise between lighting and exposing for the look you want with a little wiggle room by giving yourself a bit more exposure in case you went too far or need to bring some element in the frame up, etc.

In the days of shooting film, I used to rate 500 ASA stock at 320 ASA, but then would expose a dark scene as dark as I felt was correct, knowing that if I decided the right look was to underexpose by 2-stops, I actually had only underexposed it by 1 and 1/3-stops because of my rating. A similar thing happens sometimes in digital -- if I light a scene at 800 ASA and the director tells me it should look a little darker, instead of closing down the iris a little more, I drop the ASA down a little, from 800 ASA to 500 ASA, for example. This has the effect of darkening the shot but protecting me noise-wise. Because I've learned over the years that some directors want things darker on the set but in the final color-correction, they want things brighter. I don't know why, but it happens over and over again. Partly it's because of the classic problem where a director confuses a dark-looking scene with one shot in low light levels, when in truth you could make a scene look bright and flat while working in low levels of light, and conversely, you can make real bright sunlight look as dim as moonlight, so what matters more is exposure and contrast, rather than the actual light level on set. The other thing is that after editing a movie, there is a desire to make sure that the audience can see the actor's face and expression most of the time and follow the action clearly, so the same director who wanted things darker and darker on the set now wants to bring things up in post. Which is fine if you didn't underexpose everything in combination with a high ASA rating with a moderate level of noise all around.

Occasionally I get to work with directors who want things even darker in post, which is cool. Most DP's like things timed on the darker side than what the studios, networks, etc. want so it's great when a director backs you up on this and wants to really push the mood.