Using a light meter for digital video

[Matt Iacono]

Hello,

When you are metering a scene, do you meter for the camera's dynamic range, or for the 6 stops in SDR or the 13+ stops in HDR?

For instance, if your camera has 6 stops of highlight dynamic range, and 8 stops of shadow dynamic range, do you keep everything in your scene between those 14 stops or do you keep everything in between the lets say 6 stops of standard dynamic range?

I hope this question makes sense!

Thanks in advanced to anyone who can help!

- Matt

[M Joel W]

Personally, I aim to keep everything (except point sources and specular highlights) within the camera's dynamic range. You can always burn highlights out in post or lift shadows (to an extent).

However, I suppose if I were after a really punchy, rich, vibrant look I might aim to shoot really flat and add a high contrast grade. I'd never considered it, but using an ND grad filter would be an interesting thing to try instead of a power window, however I sold mine once I got a camera with dynamic range similar to what you mentioned above. I wonder if it offers any advantages.

I think color negative film looks different from digital in a way where a lower contrast scene can appear more vibrant, and there's an interesting LUT I saw that emulates this but it occurred to me most while watching 90s blockbusters. Regardless, those films were exposed for the film then telecine'd for video without throwing away half the dynamic range, so I wouldn't do that with digital, either.

For me, I would worry about exposing properly at key or where I want to be relative to key first (not the case with those who strictly ETTR with digital), then I worry about not losing highlight and shadow detail, and adding fill or an ND grad or streaks and tips or a flag or ND gel or whatever as necessary.

But aesthetics are a separate concern. If I want a very rich image, I might worry about my contrast ratios and keep them conservative then add contrast in post. So I wouldn't say shooting for a smaller dynamic range is strictly crazy, but I would say it's a stylistic choice, not a technical one.

I do find that these cameras encourage lazy lighting, and if using a lot of light gets you an image you like, go for it.

Edited August 3, 2019 by M Joel W

[Matt Iacono]

Understood. Thank you for the response! 

[M Joel W]

Look for responses from others, too. I'm an amateur DP (work in post), but I know a bit about HDR/SDR workflows as a result, too. So take the above with a grain of salt.

[Michael LaVoie]

I find that if I use my light meter and cross check results against a rec709 waveform and stay within that IRE scale while shooting LOG or RAW there's plenty of room to manipulate the image later because I've already restricted the exposure range.  

You can shoot tests with greyscale charts next to faces and see how the camera handles different skin tones under different light. Meter those 18% grey charts, spot meter the faces and cross check that with the camera's waveform or the NLE's waveform to determine a guide for yourself.  You could probably do the same test with an HDR workflow and get familiar with those readings as well.

 

[Matt Iacono]

This makes a lot of sense. Thank you for the response Michael! 

[Max Field]

You have the right idea of counting the stops up and down from middle grey within the camera's native DR. Let's you go in and manually take care of thing if you find the Rec709 conversion to be too punchy.

On the other hand, I really only ever meter when shooting film. A color monitor in Rec709 has worked fine as my meter.

[Bruce Greene]

When I first started shooting digital capture, I metered and lit for a "film" look.  IOW, the meat of the image within the 6 stop range, with the extra highlight and shadow detail for rolling off into black and white.

But, over time I've adjusted my approach to using much more of the dynamic range of the camera for presentation and using less for rolloff.  So, I'm lighting much more high contrast than I used to, and grading with a much lower contrast.  Kind of like lighting for 10 stops of DR rather than 6.

For a day exterior, this doesn't much matter as I have little control over the lighting, but if I have a deep shadow area and a sunlit area in the same shot, I might not fill in the shadow area at all or little.

Note that when using this technique, one must carefully watch the clip points of the image as there can be little room for recovery in post color correction.

And if you are metering with this approach, a spot meter can be useful, but you must run some tests so that your ISO setting on the meter corresponds to the recording of the camera.  So, ISO on the camera might not match that on the light meter.  Of course you can also use the waveform or other tools from the camera and/or display but they must not be viewed through a REC709 LUT or you won't see all the information.

[Matt Iacono]

Thank you Max, and Bruce for sharing your approaches! I appreciate your explanations.

I guess it's safe to say that there is no right or wrong thing to do. At the end of the day it comes down to what your intentions are as far as contrast etc. So I will experiment with different approaches and gain an understanding of the different outcomes. It seems like the safe bet is to keep whatever part of the scene you don't want to lose within the 6 stops of SDR, this way there is no need to create power windows in post, or just have a flatter image, and it gives you wiggle room later.