CAMERAS: A New Chart for Film-Style Production—The DSC OneShot
The days where we could set printer lights using a simple gray card are gone. This is a chart for the new digital "raw" and "log" age.
By Art Adams | September 04, 2012
In the old days of video, what we saw was what we got. Now, with log and raw, the possibilities are infinite. Only one of those possibilities, though, is what YOU want. Here's how to make sure your vision is the one everyone else sees.
I'll be showing off this chart at IBC, Sept. 7-11. Look for booth information at the end of this article.
We live in a digital intermediate/telecine world, which is wonderful as we can shoot HD and expect our footage to end up in a grading suite, where the number of looks available is nearly endless.
The downside is that the look we envisioned is not always the look that's created by a dailies colorist.
If dailies don't resemble the look we've promised then our days on the job may be numbered. The director and producer may decide that we can't give them the look they want--the look we agreed on in advance--when the problem actually lies off set. Or, if dailies come back looking okay but not exactly the way we want them, the odds that we'll be able to change the grade during the final online or DI is slim: directors and producers tend to fall in love with the dailies grade during the edit and often resist changing the look later.
There are several software packages that allow us to communicate with a colorist by emailing files and images back and forth. Some of these cost thousands of dollars and require the colorist to have a copy of the same software that you're using. Ultimately, though, if we start off with a common reference and then adjust a still frame in a common picture editor using only the controls that a colorist will have available (overall exposure, contrast, overall hue--no curves or power windows) we can create 80% of the look using basic image editing tools, and then let the colorist take over and finesse it. (Colorists will always do a better job at grading our footage than we will, as that's all they do and they know all the tricks. It's not hard to learn to do 80% of a grade, but the last 20% is the hardest and makes all the difference.)
Color charts are that common reference. If we shoot a reference in the real world, and the colorist knows how that reference is supposed to look, she/he can use that as a starting point to either grade your image to be as color accurate as possible, or to add a consistent look to the footage by balancing to the chart and adding in a pre-built look.
The broadcast world lives and dies by the ITU 709 HDTV standard (also known as "Rec 709", for "Recommendation 709"), which defines (among other things) the primary colors that every television in the world must reproduce in order to display color accurate images. That triangle of very specific hues of red, green and blue is the palette from which every color in a TV program is reproduced. If we have an instrument that can measure where those primary colors fall, and if we shoot a chart containing those primary colors, we can quickly grade the footage containing the chart so that colors are reproduced as faithfully as the camera allows.
The ITU 709 color space. The corners of the triangle represent the exact hues of the three primary colors necessary to create every possible color combination visible on your TV. The image is balanced roughly for daylight: the D65 notation in the center of the triangle shows that neutral white is pegged at 6500K.
We have an instrument for measuring color objectively: it's called a vectorscope. We also have access to a number of charts containing these key primary colors, including the one I'm focusing on in this article: the new DSC Labs OneShot. I designed this chart to bridge the needs of film-style production and video post production.
Using a vectorscope, together with a waveform monitor, we can quickly "zero out" an image so that colors are reproduced as faithfully as HDTV will allow. There are several ways to use a chart like this:
To communicate with a colorist by saying, "Here's a properly exposed chart--everything that follows is pretty much the way I want it. Leave the dark shadows, leave the blue moonlight, I really want that moody feeling. Don't 'save' me by making everything bright and neutral."
To ensure that product colors are reproduced as accurately as possible (such as making sure that a Coke can is reproduced as "Coke red.")
To allow a colorist to more easily correct for lighting anomalies on location. Seeing the ITU 709 primaries lit by fluorescent light, for example, will help them remove the green cast and boost undersaturated colors.
To show the colorist a starting point from which your pre-determined look can be added. If the two of you come up with, say, a bleach-bypass look with a blue hue, shooting this chart at sunset will allow the colorist to quickly dial out the warmth of the setting sun and add your predetermined cool and contrasty look to the balanced footage.
The DSC Labs OneShot provides all the color and luminance information necessary to reproduce color accurately in one quick shot.
Normally DSC Labs charts are manufactured with a glossy finish, which improves both color accuracy and increases the chart's contrast, but these charts are most often used by large productions with multiple cameras (such as the Olympics) who have the time to line up all the cameras in front of a perfectly-lit chart, eliminate all the reflections, and paint them to match perfectly. Film-style productions tend to work a lot faster, and there's no time to set up a glossy chart and then flag off the reflections of the crew and the set.
For that reason the OneShot is a matte chart. There are advantages and disadvantages to this:
Matte charts are subject to flare, while glossy charts are subject to reflection. It's easy (but time consuming) to observe and remove reflections in a glossy chart, but not very easy to observe and remove flare in a matte chart.
Matte charts are usually much lower contrast than glossy charts. Matte surfaces don't allow for the printing of a true deep black, while glossy charts (without reflections) yield a much darker and richer black.
The OneShot is unique in maintaining the most dynamic range possible in a matte printed chart by using an "AcuTech" black chip with a gloss finish. This is the same process used to create DSC Lab's Chroma Du Monde charts, only in this case it is applied to the black chip only.
This AcuTech black chip is 1/2 IRE brighter than DSC's cavity black, in which the black chip is a hole in the center of the chart backed by a cavity lined with black velvet.
Applying this finish to a single chip is an ideal compromise between a full-on AcuTech glossy but reflective chart, originally developed for the U.S. space program, and the speed and efficiency of a matte chart, which can be shot quickly without the need to remove unwanted reflections.
There's a reason that pure black in video is referred to as the "pedestal": everything in the image rides on it. Capturing a color accurate image is impossible if the pedestal is not balanced to be pure black. (I once had a shoot where a blond woman's hair appeared green while everything else in the shot looked normal. After some hurried checking we discovered via the vectorscope that the pedestal wasn't neutral. Once we balanced it the woman's blonde hair became the proper color--and we pulled a LOT of minus green gel off her backlight.)
Matte charts are still reflective, but the reflections are less obvious. If you're shooting a day exterior it's probably a good idea to tilt the chart away from sunlit grass to avoid a green tint, for example. You won't see the actual reflection of the grass the way you would with a glossy chart, but some green flare may still be present. (This is true of any matte chart.)
Lets look at how this chart really works, on the next page...
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