This is getting bad

[Blaise Douros]

Look at your waveform monitor on the first example you posted, with the screenshot. You’re completely underexposed. Your skin tones are sitting at 50 IRE max, and the usual ideal range highlight range for white peoples’ skin is around 71 IRE (obviously not specular highlights).

I think I know what the problem is, too. You’re shooting in too flat a profile, and you’re not used to it, and I think you’re making an extremely common mistake.

See, when you shoot flat footage (or log footage, which I’ll get into in a minute), everything starts to look washed out and low-contrast. And what are we conditioned to do from our prior experience when something looks washed out? Drop exposure so the monitor looks good. So you drop the exposure a stop or two, and the flat or log footage starts looking a little better, it makes you feel a little less stressed about it on set.

Your eye, and your prior experience, are lying to you.

See, the whole point of flat footage is that it looks washed out so we can unsqueeze it later in post. but when you drop the exposure so it looks better in the monitor, you underexpose the whole scene. When you try to bring up the highlights, you’re actually having to bring them up too far, and you’re seeing the results here–clipping.

So here’s what you need to do: you need to shoot the same scene, twice. Once with settings zeroed out, standard color profile, so you can get your exposure correctly dialed in with NORMAL color. Then, switch to your flat settings, change NOTHING, and shoot the same shot. If you have an 18% gray card that you can hold in the image, then that’s even better–more on that below.

Now you have a baseline for comparison–you can see where your waveform should be for a correct exposure with your flat settings. You also have a chance to make notes and build a template of settings to desqueeze the exposure from the flat settings–a DIY LUT, basically.

If you’re shooting in a true log format, then part of this process becomes a lot easier–you can use a LUT to do the initial desqueeze, and then season the look to taste. There are also exposure guides for log footage that can help you on-set; guides that tell you what IRE an 18% gray card should be at for proper exposure, that kind of thing. Because you’re building a de facto log exposure through your camera settings, you don’t have an easy solution for this (unless someone has already created it), so that’s why you need to do your comparison work ahead of time.

The fact of the matter is, there’s only so much color and exposure information present, even in the fabled GH4. It doesn’t matter how high the bitrate is, there just isn’t as much information in 8-bit 4:2:0 footage as there is in 10-bit 4:2:2, for example. Which is why you need to expose GH4 footage much more carefully than you would a more robust codec–you just don’t have the grading latitude that you would in a more robust one.

[John Pale]

Thanks for posting that Blaise. Even though I am not a camera operator, I’m keeping this one.
Dealt with grading some bad looking flat/log footage recently and now I know what went wrong on the shooters end.

[Duke Sweden]

ok, first off thanks for taking the time to write all that, buy my problem isn’t knowing how to use the camera, it’s the sudden change in quality from what I’m setting up for and the actual result. Here’s another example from today. I set up in my bedroom with natural light. It was bright in the room but no direct sunlight. I adjusted exposure (using the histogram), but when I went to adjust white balance, the white card, which was NOT in direct sunlight, just glowed like the sun and I couldn’t even adjust because the camera said it was too bright. Looking in the LCD it appeared like ball of light it was so bright. Out of curiosity I lowered exposure until I actually could take a white balance shot and, the scene was so dark you couldn’t make out anything.

Obviously my camera went out of wack for some reason. But, again, thanks for taking the time to write all that. I’m sure there’s stuff in there that WILL help me at some point.

[Blaise Douros]

The only other thing I can tell you is that your screen brightness may be screwed up? If your monitor settings are weird, it might be causing you to expose incorrectly to compensate.

Duke, I’m sure you don’t have a problem using the camera. I’m telling you that exposing for flat color needs to be done completely differently from how we were all taught to expose for standard Rec709 gamma curves.

The first time I shot a project in Slog3, I royally f*cked up the exposure for the exact reasons I specified above–the only thing that saved me was that the codec had enough leeway that I was able to salvage it. But if I’d had any real grading to do, I’d have been royally hosed. I’ve dealt with many, many other shooters who have made the same mistake, too–and it all comes from the same reason: not understanding how log exposure works.

The first thing you need to know is that the histogram is not as useful when you’re shooting flat footage as it is when you’re shooting standard gamma. The graph is going to be compressed toward the center of the histogram–in post, you’ll apply curves that will increase the contrast, while allowing you to keep detail in the highlights or shadows as necessary.

So in flat footage, if you’re exposing your histogram with the blacks just kissing the left of the histogram, like we’ve all been trained to do, then you are underexposing the image. Similarly, if your white card is sitting at 95 IRE, then you’re way overexposing. That’s why it’s crucial to do the test that I described above, so that you know where you need to make adjustments in your exposure for different kinds of conditions. You CANNOT expose flat/log footage the same way you expose a standard Rec709 gamma image–not if you want to get good results. And many of the problems you’re describing with the footage not looking the way you want it to look are completely explained by this.

When I say you may not understand how to expose log footage, this is not something to take offense at, because I’m telling you from my own experience, and the experience of some really top-notch DP’s I know, that it is super common. I learned it the hard way, and then I had to teach a DP with twenty years more experience than me how to do it. It’s not because he’s incompetent–the guy is a much better DP than me, with oodles more experience and twice the talent! But he hadn’t used the tech, and I had. Now he’s back to kicking my butt.

Have you tried color correcting that image that you labeled as three stops overexposed? Incidentally, how did you determine that shot was overexposed? Because the result looks correctly exposed.

[Duke Sweden]

Because I purposely overexposed it. Those three shots, as labeled, were under, perfectly, and overexposed because, as I’ve said, for the past week now, I’ve been doing everything I always did with great results, and suddenly I’d open my files on my PC and they would all be waaay over exposed, so I was testing my settings.

Just to be clear, again, I’ve been shooting flat for over a year, and while I am in no way in your league or any of the others here who always help me, I’m not, at this point, some guy who decided to get into video and layed out $5 grand with no idea what I’m doing. However, your posts have shown me the CORRECT way to expose, and use scopes. However, I don’t have an ATOMOS external recorder so I only have the histogram to rely on and, incidentally, I have been using it correctly, getting the peak in the middle of the scope. However, in this past week, when I hold a gray or white card in front of the lens, the histogram goes OFF the scale! There’s nothing there. I have to drastically lower exposure for it to show up again. It’s like my dynamic range has suddenly dropped to 2 stops!

Anyway, I’ll try your suggestions, but I’m still convinced something went weird with the GH4. Thanks again.

[Duke Sweden]

OK, got somewhat better results this morning but, again, white balance is way off. It used to be no problem but I guess I’m going to have to set it using the built in Kelvin scale. Here’s straight out of camera. White balanced using a 17% gray card (they’re cheaper than 18% cards. Did you know that? j/k ;-)). I exposed and white balanced on Standard Profile, shot a few seconds, then switched to Cinelike D.

Here’s the Standard:

Here’s Cinelike D:

[Duke Sweden]

ok, FINALLY. My kelvin white balance was close but not quite but, then again, I’m trying to set it according to my failing eyes. But the manual white balance came out perfect and I’m able to grade my video much more easily than the past week. I’m including a screen shot here. This, to me, looks perfect (I like my video a little darker) but please do let me know how it looks on your calibrated monitors. Too light, too dark, waaay too dark, or good. This way I can get an idea of how off my monitor is.

Thanks in advance

[Blaise Douros]

Aha. I think I see the problem here, or at least, one problem. You may be relying too heavily on the histogram to expose your image. Histograms aren’t that useful in video, because they don’t tell you what part of the image is correlated to your exposure graph on the histogram. It just tells you how much of the image is falling within a certain exposure level. That’s why scopes are useful–it tells you what part of the image is where.

A properly exposed histogram is not always a mountain in the middle of the scene. If you were shooting a low-key scene, then the majority of the histogram would sit at the left in the blacks, with a spike further up where your bright spot is.

So when you say that the exposure on your first examples were perfect because you set it up perfectly in the histogram, that’s where you’re running into the problem. A properly exposed image is exposed correctly for the scene–not a one-size-fits-all get-the-peak-in-the-middle approach on the histogram. Because I can tell you, just like you can tell, from looking at the actual image result, that your “perfectly exposed” example was not perfectly exposed; it’s several stops under. Your “overexposed” example was actually much closer to a good exposure for the scene.

I don’t know the GH4 at all, and have never shot with it, so maybe there’s some weird exposure compensation setting that got bumped that is screwing you over. But reading your post, I get the sense that you’re judging your exposure too much by how you believe the histogram should look, and not enough by the actual image.

As I understand it, the GH4 is capable of displaying zebras; if you don’t use them already, you might want to look at doing so, because they will be a far more useful tool for your overall exposure than the histogram will. But again, you will need to adjust your use of them to reflect your flatter profile.

Personally, I’m at the point where if I’m not shooting in a standardized logarithmic gamma like Slog3, I’d just shoot a standard Rec709 profile, especially when you’re working with lower-bitrate footage like the 8-bit 4:2:0 that the GH4 records internally. The footage just doesn’t hold up to any real adjustment in post, and especially in the highlights, you get weird saturation artifacts as the software tries to interpolate color information that just doesn’t exist. There are just too many variables involved in exposing for a nonstandard, undocumented flat profile like the one you create when you just desaturate the in-camera capture settings. That way, I can use known exposure values in both contexts–I know how to expose Rec709 correctly because that’s what we’ve all learned to expose from the beginning of video, and I have lots of documentation that helps me expose a standardized log gamma format like Slog3.

Now on to your examples below. On the first two examples, I really am not seeing white balance issues. The color is perfectly appropriate for the scene. And the exposure looks good, too. Your third one, where you’re holding the grey card, looks about a stop underexposed.

I initially judged that by eyeball. When I drop #3 into PS and isolate the gray card, it confirms my suspicion; it is sitting around 30-35% on the histogram, which is low. You can even see this on the full image histogram–there’s a spike (since there are a bunch of pixels around the same exposure value) around that 30-35% mark that stands out along the rest of the image.

Now, not all gray cards and not all cameras are created equal, so this is a very generalized way to judge, and is also very contextually dependent on the type of light and the overall scene. But in a very very general sense, you want that gray card to sit around 43-50% (or 43-50 IRE, on a scope) when under your keylight, shooting in a standard Rec709 gamma space (i.e. NOT flat). You might want it to be a little lower if you’re in strong direct sunlight. But at that point, you want to confirm that your histogram is actually showing a reading from ONLY the gray card–position it in your scene, then zoom in so that it fills the screen–then look at your scopes/histogram. That gets you most of the way there, but you then need zoom back out to make minor adjustments depending on what’s in the frame–if you don’t have any deep blacks in the frame, you shouldn’t be darkening the scene down so that your histogram shows a bunch of stuff in the blacks. Similarly, if you don’t have anything in the scene that should be clipping, don’t push the exposure up just so that you have an even histogram.