Topics

Measurement tools (was: Filmlook or TV?)

Adam Wilt
 

Do we need new testing methods and measurement tools? Do we need a new Gray card? Would it even be gray?

Amusingly, the humble gray card is probably the single most universally recognized reference standard across film, still photography, and digital motion imaging. So yes, it’ll be gray!  ;-)

Does a gray card, Chroma Du Monde, or other charts deliver completely useful information today, as they did the day they were released?

As our medium’s capabilities expand, these tools cover less of the total range of possibilities in one single frame, but yes, they’re still highly valuable.

Do waveform and vector scopes give us exact and useful information as they did four decades ago?

Yes, absobloodylutely.

 Are they not able to measure critical information and give useful, accurate info? How do you quantify the “jello effect", or image aliasing, or "tearing"? 

You use different tools for different problems. Not sure about “tearing”, but resolution trumpets and zone plates work great for aliasing, whether it’s standard-def or 8K. For jello, the relevant metric is the time difference between top of frame and bottom of frame. I measure it (accurately enough for our purposes) using a C-stand, a long lens, a fluid head, and a T-square (metric, of course), ‘cause I’m a high-tech guy and that’s how I roll.

Does it make sense to point to Pantone colors that correspond to primary, secondary, tertiary colors and skin tones?

The Pantone empire was built upon just such endeavors. 

Color reproduction across dissimilar media is a fraught topic; two words — metameric failure — only hint at the devilish rat’s nest of complications involved. Once you start exploring it, what’s remarkable is that we’re able to match colors as well as we can. 

Even printing a test chart with “correct” color turns out to be rather a bit more complex than you might think.

How do LED emitters, daylight, tungsten, HMI and other lighting sources affect the sensor and how do we measure that?

The TLCI is the most ambitious attempt I know of to quantify this, but due to the complexity of color there’s still nothing to replace shooting a hair & makeup & fabric test with the same lights and cameras you’re going to use in production. See the AMPAS Solid State Lighting Project for a superb overview of the difficulties involved.

Is there a neutral standard that can be formulated? Do we want one?

There are many such standards (most from the TV side of the business); whether they are “neutral” is a matter of semantics and/or religious dogma. Do we want them (in the non-TV side of the business)? Many wars have been fought, and blood is being spilled as we speak, over this contentious question!

It seems that for something like a multi cam shoot, it would be ideal to have a dead neutral camera setting that can match across manufacturers.

Yes, it would be, and live TV folks work long and hard, using standard references and standardized settings, to get as close as possible when they have to match cams from different vendors. Consider what needs to happen when you want to cut from the main studio in London to an affiliate newsroom in Tokyo, and have the pictures match. The trickiest problem is that minute differences in the spectral sensitivities between cameras from different vendors (sometimes even between different camera models from the same vendor) can put an indelible fingerprint on the image, making an exact and perfect match impossible — as I discuss in that “Correct Color” article.

There are a lot of things that cameras do that we want them to do and there are a lot of things we don't want them to do.

Are there tools to measure these different characteristics?

There are lots of tools, but the useful ones beyond the standard charts ’n’ stuff tend to be specialized to look at one thing or another, so you wind up with dozens of different metrics for abstruse parameters, some of which may not relate to image quality or characteristics in any significantly satisfying way. In the end — at least if you’re not trying to match broadcast cams — these tools can only get you part of the way there. 

There’s nothing yet devised that beats looking at scenes on a properly-calibrated monitor for literally getting the whole picture. 

Adam Wilt
technical services: consulting / coding / camerawork
Vancouver WA USA (no, not that Vancouver, the other one)

Mark Sasahara
 

Dear Adam,

Thank you for all of your information and links! I realize that I use charts and scopes in a basic way, so this discussion has been very educational and expanding, for me.

Yes, charts are all well and good, but there's nothing like an actual scene with movement and humans to get more specific. Especially, if I am going for a certain look, or feel. Then you start throwing in lenses and lights and the whole thing goes to hell.

As I say: It's gonna get real bad, real fast.

But it is good to know more about what I am looking at/for when I frame up a chart.

Best,

-Mark Sasahara, DP, NYC

Mark Sasahara
  marksasahara@...
   718-440-1013
    http://msasahara.com


On Mon, Jun 25, 2018 at 2:39 AM, Adam Wilt <adam@...> wrote:
Do we need new testing methods and measurement tools? Do we need a new Gray card? Would it even be gray?

Amusingly, the humble gray card is probably the single most universally recognized reference standard across film, still photography, and digital motion imaging. So yes, it’ll be gray!  ;-)

_._,_._,_

Art Adams
 

Yes, charts are all well and good, but there's nothing like an actual scene with movement and humans to get more specific.
_._,_._,
That's the ultimate test. Charts are good at predicting what you'll see in such a scene, and good for figuring out why something in the scene doesn't look right, but an actual scene is the way to go.

--
Art Adams
Director of Photography
San Francisco Bay Area