1) pre-production: during the check out and adjustment of HD cameras;
2) production: as color and tonal reference for creative ideas on the set;
3) post production: as a connecting element between cinematographer and online colorist.
As a result the "Gamma-HD1" chart helps the cinematographer and online colorist achieve color-accurate and contrast-consistent dailies either in the tape-to-tape or tape-to-film transfers .
Charts Elements:
1.Seven field gray scale helps to adjust proper luminance (brightness) of the scene, camera gamma settings and related voltage output. Each field is calibrated in T-stops clearly marked on the chart. Those fields represent the practical latitude (density range) of current HD technology.
2. Black velvet patches as reference for minimum, black field voltage respond.
3. Ramp (linear sweep) scale shows the relationship between voltage and brightness as a continuous line or a characteristic curve. This curve is especially helpful during the knee, b/w balance and gamma adjustments.
4. Twelve Color Fields are designed to compare the color sensitivity and color bias of different cameras. The enclosed graph indicates the placement of each color on the vectorscope
5. Three "Easy Recognizable Colors"TM: sky, greenery and skin tone are samples of the very few colors that people from all over the world readily agree on and experience practically every day. Those colors also help to facilitate communication between the cinematographer and colorist.
6. Voltage Aims Indicator (VAI) is a removable magnetic strip that represents the image adjustment targets for optimal tape-to film transfer process. Two VAI marked S and E (for Sony HD Center and E-film, Los Angeles, respectively), represent desirable voltage values for tape-to-film transfer with two leading facilities in Los Angeles.
Those voltage aims help transferring facilities to create color-accurate and contrast-consistent film negative which fully represents all the original tape values and will be printed to film positive using optimal, middle range printing lights. We plan to expand the list of facilities and add more Voltage Aims Indicator Strips.
How to Shoot the Chart:
Please illuminate the chart at the same F-stop that you will use to shoot the actual set or scene. For the best results in color correction and contrast adjustment, the color temperature (TºK ) of the light on the chart must be the same as TºK of the light illuminating the set.
1. Record a slate to indicate that a calibration chart is being used.
2. Shoot the chart full frame for a few seconds.
3. Frame up the section of the chart outlined in green for online gamma adjustment. This section (in 16:9 ratio), includes greyscale and VAI and help the colorist to have a clearer view on the waveform monitor.
4. Shoot the chart on the first roll of each day and every time the set or light conditions are changed. If every set or scene has a different look, as is common in commercials, documentaries or industrials, then shoot the chart at the beginning of every scene or set up. This will allow transfer of the maximum data from your tape to the negative.
5. Shoot the chart twice when your set is lit for a special effect (i.e. sunset or you are using color filters)
5.1 Shoot the chart under "normal light", without color filtration on the source or lens . Slate the chart with words "TRANSFER FOR GRAY."
5.2 Add the filter on the lens or gel on light, and shoot the chart a second time. This time describe the look you intented. For example, "TRANSFER FOR SUNSET" orv "TRANSFER FOR NIGHT". This will indicate to the colorist that the set is lit with "sunset" or "night" light intentionally, and there is no need to "correct" the color of the scene.
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