September 19, 2014

Histograms: Helpful Exposure Tool, or Should You Avoid Them Like the Plague?

Indie Cinema Academy - Ryan Walters - Histograms
A few months back, we shared some tips on how filmmakers can use histograms to properly expose their images. Despite the fact that histograms can be a helpful exposure tool in certain situations, there are quite a few downsides to using them in a filmmaking setting. Cinematographer Ryan E. Walters explains:

The most common criticism of histograms is that they're wildly inconsistent. For instance, it's almost impossible to look at just a histogram and tell whether the image it's representing is properly exposed or not, as can be seen in Walters' example in the video above. With that said, however, given that the shooter knows the context and style (whether it will be dark, bright, balanced, etc.) of the image they're creating, the histogram can be an excellent visual reference tool. If you know that you want a dark, contrasty image, or a bright, washed-out image, a quick glance at a histogram will tell you if you're on the right track. Then again, for judging over and underexposure, a waveform monitor is a much better tool.

Then there's the issue of Exposing to the Right (ETTR), a practice widely used by stills photographers to maximize the range of luminance values captured by the camera when shooting RAW. In theory, ETTR is a solid practice because it results in cleaner images with less noise in the shadows. As such, ETTR is the law of the land when exposing with histograms for many photographers. However, for filmmakers, many of whom are shooting on 8 bit 4:2:0 cameras with limited dynamic range, ETTR can be a risky practice because it can very easily lead to accidental overexposure and unrecoverable highlights, especially if the histogram is the only exposure tool being used. Then there's the issue of maintaining exposure continuity throughout a range of shots. As can be seen in Walters' example, ETTR can lead to some unsightly shifts in exposure between shots if you're not extremely careful.

Ultimately, the histogram can be a helpful exposure tool when you need a visual representation of luminance values within a certain shot. It can help you determine whether or not the camera is exposing the way you want it to be, whether dark, bright, or neutral. However, histograms should almost always be used in conjunction with other exposure tools like waveform monitors, false color displays, and zebras. If you rely on the histogram alone, you might be in for some unfortunate exposure surprises when you review your footage.     

Your Comment

31 Comments

How does your colorist know which look to go with? Communication. If you aren't communicating with your colorist, good luck getting what you want...

Noise levels changing? Denoise and add film grain. If done properly it WILL look better... And the more you expose the image the less noise there will be to begin with...

Exposure changing from shot to shot? That's just a fact of life unless you are shooting at the same aperture all day. Which no one really does unless they're a Vimeo film kid with a DOF fetish. Do what any real filmmaker or colorist does and HANDLE THAT SHIT.

September 19, 2014 at 3:13PM

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Angus Lyne
Filmmaker and VFX generalist
315

Communication is key for sure. No argument there. :)

What about the shoot where the turn around is to tight, and interfacing with the colorist doesn't happen? What if you're off to the next project, and they need input, but you're not available?

Denoising is also possible. And if you have the time to do that, great! But how many productions are taking the time to do that, and of those that do, how many are doing it properly?

Shooting at the same aperture is standard practice- at least when you get to higher end work. When you change the aperture, not only do you change the exposure, but you change the depth of field, the contrast levels, the look of the bokeh...

Anyway, I agree with your comment that you need to handle that shit. :) But in the commercial world where I work, handling that shit is done at the camera level. Productions aren't interested in adding additional steps to the workflow (means more time & money) for something that could have been (& should have) handled earlier in the process.

BTW- in the follow up video, I show how to use your histogram to get consistent results. ( http://indiecinemaacademy.com/academy/get-consistent-results-with-your-h... )

September 19, 2014 at 4:12PM

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Ryan E. Walters
Cinematographer & Mentor @ Indie Cinema Academy
154

Thanks for sharing that, Ryan. I added it to the article.

September 19, 2014 at 5:28PM

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Rob Hardy
Founder of Filmmaker Freedom
4503

DOF just like any other tool is a tool that SHOULD be used. Some shots SHOULDN'T match. In my opinion following preset rules doesn't make your work automatically "high end" unless your definition of "high end" is homogeneity... Though I couldn't disagree more. And I find it ironic that you are basically describing a corporate turn-and-burn fast food style of production, where there is no communication between departments, and the colorist is incapable of balancing contrast levels or denoising footage properly... That sounds less like the "high-end" and more like Reality TV production...

September 19, 2014 at 6:06PM

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Angus Lyne
Filmmaker and VFX generalist
315

Ryan, for years, I've never known what you are talking about, most of the time I am extremely bored but I trust you. I will break every rule you explain but I love your technical mind and I have learned SO much from your blog. You are an awesome resource to the community.

September 19, 2014 at 7:17PM

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Josh Paul
Most often DP, Direct or Gaff
1245

Keeping the same aperture is actually a pretty high-end thing, in my experience. Not shooting wide-open all the time, but making the aesthetic decision to shoot at f/4, for example, and deciding to stick with that for the majority of a shoot so shots match.

September 19, 2014 at 5:08PM, Edited September 19, 5:08PM

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David S.
2859

Some of the production guys I work with have all these rules like this and they drive me nuts. I can't stand it but they're right. I can deal with it most of the time but when the shot looks awful to begin with, I want to pull my hair out when they start nitpicking about being at 5.6

September 19, 2014 at 7:25PM

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Josh Paul
Most often DP, Direct or Gaff
1245

About the ETTR, I thought it was widely known as a technique while you're shooting RAW. I mean, if you heard that term, you probably ended reading about how it works, why it works, how to recover the footage or why use a S-log profile option... I never thought someone would use it when your file is compressed, I don't know anyone who did it.

September 19, 2014 at 3:16PM

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The same principles apply if you are shooting in raw or in a compressed formats. ETTR does yield cleaner images- but inconsistent results that require more work & time. If you know your camera, light & expose consistently, you can get the same clean images but without the post headaches of ETTR, regardless of if you are shooting in raw or compressed formats. :)

September 19, 2014 at 4:37PM

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Ryan E. Walters
Cinematographer & Mentor @ Indie Cinema Academy
154

Sound like that article i just red:

Speedometers: a useful tool, ir should you avoid them like a plague?

It had a video of Dominic Torreto saying a speedometer weights you down and instills a false sense of driving fast - prevents from keeping the pedal to the metal all the time!

Kno what I mean?

September 19, 2014 at 3:25PM, Edited September 19, 3:25PM

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Alex Zakrividoroga
Director
3843

I liked this video. It is educational. Waveform monitor is probably the most useful in camera exposure tool. I was talking to a buddy the other day and he told me that back in the day that it was common practice to pick a aperture and keep it for the whole film. He said that the godfather was shot at 5.6. That they would change the lighting to match the stop. They also used light meters back then to give them the proper exposure of middle gray. The next video in Ryan's series is about using the histogram and a grey card to get the proper exposure for each scene based on the value of middle grey. I've only watched a couple of these videos that Ryan has done but I am going to watch more of them because they really and useful and have a wealth of practical knowledge for beginning or intermediate filmmakers and videographers

September 19, 2014 at 3:54PM, Edited September 19, 3:54PM

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Peter Staubs
Camera Assistant
467

Yep, exactly- the masters of their craft (Think people in the ASC,etc) shoot a scene at a constant aperture. (Some times different scenes may have different apertures, but not within the scene.) One of the reasons for that is to keep the look consistent through the film.

For myself, the exposure trifecta is the Light Meter + Waveform + Knowing your camera.

I'm glad that you like what you have watched. There is more great free content in the articles section. (The lessons section is for our paid members.)

September 19, 2014 at 4:33PM

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Ryan E. Walters
Cinematographer & Mentor @ Indie Cinema Academy
154

This is funny timing, I was just on Reddit the other day talking to someone about this. I just got the pocket camera and decided that I'm just going to shoot RAW because it's so much better, but I've been using the histogram to really just see the full dynamic range of that camera. The shots by themselves look great, but I can see the issue when they get edited together.

So I have two questions. What light meter should I get and how do I use it? How do I even access a waveform to view data if my camera doesn't offer it in the settings?

September 19, 2014 at 8:15PM

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Julian Faras
Editor, Cinematographer, Director
373

thanks Ryan E. Walters for the concise and imho awesome input on this subject. your videos on exposure really helped me a lot. in my limited experience, I found that histograms tell me nothing that a waveform wouldn't, when in fact, they don't show a hell of a lot of information I'd want.

Next week, we'll be shooting a short film /fan video on the BMPC in 1080p ProRes and we'll be exposing by light meter and waveform. It's my first project on the BMPC and I'm excited to see the footage and what I can do with it in DaVinci.

As for the 8bit 4:2:0 party people - I've shot most of my stuff so far on 60D and 5D - I'd go for maybe +1/2 stop over on the skin tones and find this yields decent results and options in grading, but I could never achieve this with a histogram.

On the log-curve thing, in my understanding, light is always registered on the sensels in linear fashion but sampled in log (because +1 f-stop = 2x the light...) - always. Which would be why Cinestyle works. Yes/No?

September 19, 2014 at 5:02PM, Edited September 19, 5:01PM

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My biggest beef with histogram is just the lack of information it gives. All it says is somewhere, something in your seen is at this level—waveform actually shows you where in the frame each value is.

Does anyone know any situation where a histogram is actually more useful than a waveform? I haven't been able to find one, but would love to know if there is one.

September 19, 2014 at 5:11PM, Edited September 19, 5:11PM

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David S.
2859

to all those who think one doesn't need a light meter when shooting digital... i rest my case.

September 19, 2014 at 5:37PM

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Fernando Mamede
director/dp
155

Amen.

September 21, 2014 at 5:13PM

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Daniel Mimura
DP, cam op, steadicam op
2255

They have a few lessons on their site, but not enough to warrant $10 a month.

September 19, 2014 at 6:29PM, Edited September 19, 6:29PM

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Luna Videography
Videographer
604

Whether you agree with his rules and theory or not, he is an awesome resource for technical knowledge that's on a different level. You can find crazy (and sometimes boring) technical production stuff from his site.

September 19, 2014 at 7:20PM, Edited September 19, 7:20PM

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Josh Paul
Most often DP, Direct or Gaff
1245

Probably going to get made fun of for this, but couldn't you... Just look at a monitor?

September 19, 2014 at 9:37PM

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Elias Hardt
Director / 3D Graphics
98

As one tool of several, yes. But as the only tool, no. Our eyes are tricky things, and adjust and adapt far more than we realize. Going by your eyes only will lead to shots that don't match. Reliable scopes take this variable out of the equation.

At the same time, only an idiot would shoot exclusively with scopes and never check the monitor. It's a balance of what feels "right" subjectively and what is "right" objectively.

September 20, 2014 at 12:01AM

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David S.
2859

good presentation! we always relied on the middle grey and of course our cine meter. Try to get the consistency and there at least with us are slight variations but nothing drastic and can easily be corrected in post no problems. On the comment of changing your lighting? Absolutely.

September 20, 2014 at 3:58AM

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Randall Paul
Lead instructor at PFAS ( USA) and AFSA (Italy)
190

good presentation! we always relied on the middle grey and of course our cine meter. Try to get the consistency and there at least with us are slight variations but nothing drastic and can easily be corrected in post no problems. On the comment of changing your lighting? Absolutely.

September 20, 2014 at 3:58AM, Edited September 20, 3:58AM

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Randall Paul
Lead instructor at PFAS ( USA) and AFSA (Italy)
190

i couldnt disagree more with both these videos.
in the first video he compares histograms of final color corrected/graded photographs!
you just cant draw conclusions by looking at histograms of final images and then link these conclusions to the use of histograms while shooting.
its a different thing.

by using the gray card technique described in the second video, you will very often and very easily get crushed blacks or clipped highlights not only in extremely contrasty environments but even in simple cases.

this is digital we are dealing here and the dynamic range of digital is not enough yet. so you cant just play and have fun and be creative about it. with dynamic range you have to get as much as you can. and that is done using histograms.

prolost says it all with a simple sentence:
"You should expose as bright an image as you can without clipping"
thats all there is to it.
http://prolost.com/blog/2008/3/2/exposing-to-the-left-vs-exposing-to-the...

September 20, 2014 at 10:45AM, Edited September 20, 10:45AM

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aombk
244

Most DP's I know keep it consistent. Most people expose it how you want it in camera...b/c 9 times out of ten, except on features and big budget stuff, you're not going to be there in post, and they're not going to really make that many adjustments to it...just deliver it as close to how you want it to look in the end.

Also, even if those examples are final graded shots...so what? The point he is making is clear...dark interior scenes in the Godfather 2 and scenes on Hoth in the Empire Strikes Back would have drastically different histograms, which is what Walters was showing...you would not expose those three examples (in Walters' video) to the point where their histograms would ever match and then grade them to look different in post.

September 21, 2014 at 5:36PM

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Daniel Mimura
DP, cam op, steadicam op
2255

My biggest problem with the histogram is that now very few people who didn't grow up shooting film are lighting to this instead of using a lightmeter.

This is personally annoying b/c as a steadicam operator, I don't enjoy being a 70lb human lightmeter, pointing the lens here and there throughout the scene so the DP can figure out exposure. B/c this has happened a few times with younger cinematographers, I started carrying around my own lightmeter, and I realize that a lot of people don't even know how you use it.

So many filmmakers are hyper-concerned with noise and overexposure to the point that they light things pretty flatly and boringly, just for a technical perfection out of the sensor. Shadows can be black. And car headlights overexpose.

September 21, 2014 at 5:43PM

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Daniel Mimura
DP, cam op, steadicam op
2255

WTF
This video is bollocks, sorry for the hard words but if there is a tool to understand you image better, there is no reason to "avoid" it. forget about the idea of "proper exposure". Exposure is a creative decision, in the often given example of a snowman in snowfield or in African in a dark tunnel the exposure which we would consider correct varies. This is not even the end. For A tragic scene you might want to under exposure A little, Whereas you might over exposure for a enlightening scene. There is however an exposure which is technically the most beneficial to your image. When out of doors in a very contrasty scene, let's say for example 17 stops with a 12 stop camera, it is very important to to exposure for dynamic range. You definitely want to get the most out of your highlights and shadows. Is very likely that you will have to help this scene in Post, as you might lose a lot of shadows otherwise. On the other hand is in studio with a lot of lights under your control the quality gain by exposing technically-best is close to zero (assuming that you'r light sources are strong enough that you can lower the ISO to a reasonable value). ETTL is very are useful tool here too. You might want to exposure with ETTL for your Key light and Backlight and then add your fill lights to raise your shadows till satisfied.
But back to what I was saying, histograms are good for getting an unbiased View off your exposure. They are not telling you whether you exposure is right or wrong. But they are telling you how your exposure renders the image. They are one of the three Standard tools that help you to see your image a bit more clear even without a colour corrected monitor. (the other two are the Vectroscope and the waveform) therefore use them but don't expect them to do your job!
Kind Regards
Jake

September 22, 2014 at 12:19PM, Edited September 22, 12:19PM

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According to your own words - "They are not telling you whether you exposure is right or wrong", I think thats what the video is saying.

September 29, 2014 at 3:39AM

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Kayode
918

I use an incident light meter. It's impossible to judge low-key situations with a histogram, let alone back-lit scenes. Besides, it's the only thing i can rely on when i use a camera i'm not familiar with - give me a Canon or a RED or a Blackmagic and tell me it's latitude, and i can get to work, if i have a light meter.

PS: I believe a light meter is the only tool that can teach you to light; that can teach you to have an understanding of light

September 26, 2014 at 1:58AM

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Patricijus Petrukonis
Cinematographer
147

Eh. I've always found Histograms incredibly easy to read. I don't no any pro personally, whose work is what I'd call 'good,' that doesn't know how, and when to use the Histogram and when not to.

Applying a catchall to not use it isn't much of a help to people learning. It's always, "the right tool for the job."

September 26, 2014 at 6:18PM

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Never been smart enough to get my head round the histogram. I know where my blacks and whites are but never been able to get consistent exposure. Started using a light meter a few months back and I've not looked back.

September 29, 2014 at 3:23AM

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Kayode
918