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Old September 28th, 2008, 01:40 AM   #1
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Lighting Ratio

So I find that i usually shoot at a 2:1 lighting ratio (two foreground, one background) and i find my films are just turning out to dark in general, but i still like the ratio. Would it be better just in general to shoot a 4:2 ratio, and just change it in post? I'm not really sure if this makes much sense on paper, but in my head it kinda does.
p.s. i don't know much about lighting, so sorry in advance if i misused terms or anything of the sort.
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Old September 28th, 2008, 02:47 AM   #2
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You may be misusing some terminology. A 2:1 ratio would normally be associated with something like a soap opera, sitcom, maybe news. . .that's very very conservative. It means that wherever the ratio is applied, your darkest area is only half as dark as your brightest area. Written, this may sound like a big difference, but visually, it's not much. If your films look too dark in general, I don't think the 2:1 ratio is the problem. It's that the "2" is probably not bright enough. If your brighter area was lit at an ideal exposure (unless you're intentionally underexposing some to convey a night time effect or something), your background should be plenty bright if the ratio you mention is accurate. Maybe you could post a still?

4:2 ratio, unless you mean something different, would be the same as 2:1. Usually these lighting ratios are always expressed as x:1, where x expresses the difference between the brightest and darkest parts. For instance, if we say "there's a 4:1 ratio between the key and fill lights on this character", that means the key light is 4 x brighter than the fill light. The ratio numbers do not refer to specific fstops or levels of brightness, just the difference between the two levels. If you know about fstops, 2:1 could mean that, in your example, your foreground is lit to an f2.0 and your background to an f1.4, or it could mean your foreground is lit to an f16 and your background to an f11.

Don't know if this is helpful or just more confusing.
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Old September 28th, 2008, 03:42 PM   #3
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that actually did help! but i think i'll rephrase my question a little better.
If i want a dark scene, is it better to shoot it lighter, and make it darker in post? or shoot it too dark? (as i seem to be doing most of the time)
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Old September 28th, 2008, 03:52 PM   #4
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That's somewhat of a preference, in my opinion. If you KNOW for a fact that how you're shooting is how you want it to end up, and you KNOW you're not going to change you're mind halfway into the editing process (or even the day after you shot your too dark scene), then shoot it the way you think it should look.

On the other hand, if you want room to play around in post via color correction/manipulation, you might shoot it brighter (but still exposed correctly, not over exposed) and then you'll have wiggle room to darken in post should you so choose. It's always easier to start with more light and take down the brightness (this goes for on set too, when you're setting up lights, and trying to decide which unit to use--do you use the 300w light, or the 600w light that you can put a scrim in if need be?) than it is to bring up something that was shot too dark.

If I were doing dark/contrasty scenes I would probably shoot brighter than I think I need (not by a lot, but a little), because from past experience I know I've done stuff I thought looked AMAZING at the time, and then when I came back to edit it, realized it maybe should have been brighter, so then I'm fighting a battle in post. It's hard to be properly critical on set because you're always crushed for time, even more so on uber low budget stuff. Easier to judge things when you're in a relaxed environment sitting in front of your monitor. So long story short, better safe than sorry.

You do still need that lighting ratio, to some degree, when shooting, even if you shoot everything over all brighter. If you light everything flat, no amount of post manipulation (unless you have the patience to mask and tweak everything manually--not fun) will make it look contrasty. But you can take contrast that's already there from being shot correctly and enhance it some (removing it is more tricky) if it looks too even/flat.
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Old September 28th, 2008, 03:57 PM   #5
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It's actually a bit of a complicated question and you may get several different responses to it. I have for years underexposed video and preferred the look, but you do run the risk of increased noise especially if you need to bring anything up. I've occasionally had people who like to do things "by the book" wring their hands and show me waveforms and histograms that show little in the top half, but I maintain that a dark scene is a dark scene and if the histogram resembles a bell curve, it's not going to read dark. One trick is to make sure that there are highlights somewhere in the frame which will help things from looking mushy while maintaining an overall "down" image. On a project I shot last year, I decided to experiment by setting the exposure where I liked it and then opening up 1/2 to a full stop to give a more standard exposure. Even though we did a full color correction and I brought a lot of it back down, I didn't really care for the way it looked--it had that "video" feel to it.

Perhaps you can post some frame grabs of shots that you feel represent your concern and we can make specific suggestions on how you can
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Old September 28th, 2008, 09:35 PM   #6
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The in the restaurant scene was what really bothered me:
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You mentioned the "bell curve" on the histogram, do u recommend a good book that talks about histogram readings and what not? (sorry for the question in a question)
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Old September 28th, 2008, 11:17 PM   #7
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Your lighting's quite nice on a lot of that!

Yes, some of the shots in the restaurant do look underexposed overall (that wide dolly shot with the guy in the middle of frame, for instance). For the record, the contrast in that scene looks a lot higher than 2:1 to me. You've got area that are somewhat underexposed, and then areas that go (or at least it appears) totally black. A 2:1 ratio would have very little visual difference between the light and shadow regions of each shot.

Also, how did you come to the conclusion that you were shooting the 2:1 ratio? I mean, how are you measuring contrast? Are you going by eye? There are a couple of ways you could more objectively measure your lighting, if you choose to do it that way (some people don't with video, since you can hook a monitor up and have an accurate representation of your image). If you have access to a waveform monitor, that's always good. A light meter works, and you can also use your camera as a light meter by using the zebras.
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