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May 11, 2013

Knowing Your Scopes: When to Trust Your Eye and the Most Useful Scopes of All

waveform monitor histogram after effects adobeDepending on the acquisition system, waveform monitors and vectorscopes can guide quality control of your imagery from shooting all the way down the pipeline to grading, mastering, and compression for delivery. Scopes can seem a little intimidating and esoteric to the new user, but getting the basics down can really help in owning your image. Recently, Alexis Van Hurkman over at ProVideo Coalition has answered some key questions about scopes: find out which ones he considers the most indispensable below, plus when it may be a good idea to trust your own pair of eyes in making adjustments -- even when your scopes are reading 'A-Okay.'

Scopes Don't Lie, But They Can Get Tricked: When Your Eye's the Bottom Line

Alexis kicks off his new Q/A column over at PVC by confronting a rare and dreaded conundrum, with respect to grading: what if your scopes and your eye are telling you two different things?

What do you do when you have two shots that appear to be matching on your video scopes but it still isn't matching according to your eye?

I find this doesn't come up too terribly much, or perhaps it's just that I don't really make a note of it anymore, but I'm fond of saying you should keep one eye on your scopes, and another eye on your monitor. My short answer would be, if ever the two disagree, go with your monitor.

Alexis emphasizes that this preference weighs heavily on your proportionate experience with the monitor. If your monitor's tonal and gamma responses (compared to corresponding scope readings) are familiar to you and you're comfortable and confident in its representation of key characteristics, going by the monitor is a relatively safe bet. On the other hand, if you have any reason to not fully trust the monitor, you'll have to play it closer to the scopes.

Getting back to my original point, the overall goal of shot matching is to achieve a convincingly plausible match among the various shots in a scene, and that requires you to evaluate the characteristics of each image, overall. When people watch a clip, they're looking at two things–they're focused on the object of the scene, such as a person talking, and they're also taking in the overall atmosphere of the image, whether it's bluish or orangeish, high contrast or low.

Qualities such as the more diffuse, overall color context -- the 'warmth' of a scene -- can appear more skewed one way or the other in comparison to a preceding shot, depending on the contents of each. Interestingly, this is due to some of the same principles at work in the law of simultaneous contrast -- in its most extreme case, the law dictates that two complementary colors appear their most bold and saturated when juxtaposed directly adjacent to one another. As such, the balance of ambient details can become weighted differently in perception across multiple shots, even when their scope values seem consistent throughout those same shots. Alexis points out that due to this (among other things, we recommend you read his full post), the image on the left appears warmer than the cutaway to its right, which appears cooler:

Alexis Van Hurkman pvc pro video colation scope eye shot different vectorscope waveform monitor rgb parage image grading color correction timing

This is a bit of a befuddling place to find oneself during grading, especially when comparing the two shots' RGB parades -- be sure to read Alexis's full post at PVC to check those out, as they'll yield the best comparison. As indicated above, the solution may simply be to 'go by eye,' and cheat one of the shots a little closer to the other than the scopes alone might dictate. After all, the final viewer will be judging by eye, and by eye alone!

What's 'The Scope of All Scopes'?

Alexis says that if he were marooned somewhere remote and had to pick just one scope to use, it would be the very flexible RGB parade -- but that the vectorscope would be his second choice. Vectorscopes do what no other scope can, he says, which is show you your overall color balance, which color(s) that balance most leans towards, and how saturated those dominant colors are all at once. Check his post for greater detail.

Alexis Van Hurkman pvc pro video colation scope eye shot different vectorscope graticule waveform monitor rgb parage image grading color correction timing

He's also devised (and open-sourced) a brand-new graticule for the vectorscope, which is the two-dimensional overlay that guides color calibration and context, pictured above. Color graders will have to chime in with their own thoughts, but to me, this graticule looks a lot more intuitive than the traditional one (which again, can be seen in the source post). The guidelines leading directly to the primary and secondary colors seems a lot more helpful than the concentric rings of other vectorscope models -- but again, that just might be me.

What are the scopes you most rely on in post (or on set), and why? When have you found your scopes to be 'tricked' by an edit, and what ways have you found yourselves correcting for perceptive mismatches?

[Images and information courtesy ProVideo Coalition and Alexis Van Hurkman, featuring examples from his Color Correction Handbook.]

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20 Comments

Funny, Shane Hurlbut says the opposite. He says eye is better.

May 11, 2013

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Maybe his monitor just sucks?

May 12, 2013

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Oh I doubt that.

May 12, 2013

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Sam

He said he trust his eye the most. Also says he's not a waveform/scope guy. It's in one of the podcast he's in.

May 12, 2013

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Shane uses the HP Dreamcolor. Not a cheap monitor coming in at $2,249. So I think his monitor is fine...

May 12, 2013

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Actually this is a very cheap monitor by professional standards. Not to say that it's bad, but it's definitely not expensive.

May 13, 2013

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Brian

Shane is Shane!! A super calibrated eye.

May 17, 2013

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Jair

I'm wondering, why do people make a big deal of histograms, when the waveform scope tells you so much more about the image? Do histograms just take less power to process or something?

May 11, 2013

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Sam

easier to look at imo

May 12, 2013

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Derek

It simply depends what kind of background you are in. I started as a photographer first and moved into the film end, so histograms are what I'm far more used to look at.

May 12, 2013

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Hubert

I also made the same switch... Besides, I use histograms for check exposure with direct sunlight on my camera screen... I was thinking: "hey, i might need a z-finder (or something much more cheaper)" xD

May 14, 2013

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Rafa Ga

Bruce Logan ASC discusses waveforms and light meters in this awesome interview I did (*pat myself on the back).
You can find that part of the discussion in Part 2 (second video) @16:45.

http://bigleaguefilmschool.com/brucelogan/

May 12, 2013

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The other thing Shane Hurlbut preaches is to USE A GOOD LIGHT METER instead of waveform monitors or vectorscopes in the camera. I shoot on Canon DSLRs with a Sekonic DigiCineMate (almost always underexposing by 1/3 stop) in Lightform C picture style and I get beautiful, almost perfect images from the camera that post houses rave about -- and which need virtually no color correction or grading. I think there is way too much obsession with grading and "looks." As Hurlbut and other top pros say, the rule should be "What you see on the LCD of your camera is what you get."

May 12, 2013

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John B.

An interesting point which I have heard before, but I was watching the Barry Green DVD Lighting for Film and Television recently and, unless I misunderstood, he said to go with the camera waveform as a seperate meter will not see what the specific camera sensor is seeing. Is that right ?

May 12, 2013

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Saied

Saied: Actually, that was part of Hurlbut's point -- that too many young cinematographers and depend on waveforms rather than the classic light meter. One example: With a waveform monitor, you cannot move around the set/location and get a feel for the lighting the same way you can by walking the set with a light meter and getting a visceral sense of contrast and relative under or over exposure in a particular part of the shot -- then understanding WHY you're doing that. That is the most obvious difference. Of course, opinions vary. But per my post, I am a strong believer in using a meter to light, THEN a WM monitor to check/confirm exposure (especially for highlights). The other major rule of digital cinema is to always be careful to expose for highlights because blow-out highlights can not be fixed in post. That detail is lost forever, no matter what camera you're using.

May 12, 2013

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John B.

Thanks very much John. I checked it out from Hurlburt, and his first paragraph is interesting.
http://www.hurlbutvisuals.com/blog/2013/04/training-your-eye/

May 13, 2013

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Saied

I wish I had a fiver for every time some "pro shooter" said "you don't need a light meter... there's one built into every digital camera."

As for me, I use a Spectra-Cine Pro IV-A.

May 16, 2013

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Zan Shin

Just wanted to differentiate something: Hurlbut is talking about not relying on scopes when he shoots, especially in-camera scopes on the DSLR's. His post people ABSOLUTELY use scopes, and have even posted on hurlblog about their procedure...

May 14, 2013

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I'm very much a waveform/vectorscope guy. And the one I use mostly is the waveform as it tells me much more about the image that I need to know.

Also, I've been on the verge time and time again to get a light-meter. Though I have been doing pretty good without it. Using ML with the Zebra and built in waveform. What I would need it for is the old argument of replicating lighting on another shooting day or set. But I haven't been in that situation enough to warrant this yet....

oh all right. I'll look into the prices for a light-meter once more. :)

May 14, 2013

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Thanks for this excellent post, but I'm not sure why there'd be any debate. If a certain colorist says he trusts his monitor when it disagrees with his scopes, than that's the result of his experience with that gear. If any of us would do differently, that may be because we have different gear or different experience.

We should all be content doing what we discover works best for each of us. Hopefully that discovery comes from more than reading articles on the internet.

May 16, 2013

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