CINELITE On-Picture Exposure Measurements
Designed with feedback from both film and video professionals, this new on-screen measurement option offers additional measurement functionality on award winning Leader HD and SD monitors. Essentially providing the function of a spot light meter, CINELITE provides on-picture measurements of video levels in % RGB, Y percentage and f-stop readings, bridging the gap between film and HD production measurements.
For the first time in our industry, you can now review and evaluate your set, after the camera has processed the image. Point a cursor to any position on the picture to get instant measurements in f-stops (or percentage) and review the material that is actually being recorded. Final adjustments of lighting conditions, filtering and iris adjustments can be made using familiar gf-stop h based evaluation techniques.
CINELITE® is very useful for Scene Matching – this tool allows you to change cameras or camera positions in a scene and verify that their outputs are producing the same picture values as before. The resulting measurement is digitally accurate and represents the material as it is actually recorded. This ensures scientifically accurate communication with the post-production and color correction process while enhancing the understanding of film and video experts alike.
CINELITE® f-stop measurements allow DPs and cinematographers to evaluate their HD or SD production using the same measurement techniques that have produced excellence with film over decades. Essentially, the CINELITE® option allows HD production professionals to evaluate their lighting and exposure in real time and helps create a set-evaluation and exposure determination workflow environment similar to working with film.
CINEZONE Exposure Zone False Colors Display
Instant view of your lighting conditions and easy determination of exposure zones. CINEZONE overlays false colors on the image—the colors are determined based on the scale on the left; blue indicates near-zero values, red indicates values at 100%. This helps confirm your camera is reproducing what you expect. As a side benefit, shadows are highlighted in blue, making it a lot easier to examine shadow detail using the CINEZONE display. Adjustable upper and lower limits add black and white color overlay to indicate under exposed and over exposed conditions without having to reference the waveform monitor.
CINEZONE display sample, left; Original image below.
Combination screen showing on-screen spot measurement of RGB.
f-stop (bottom-right), false colors display depicting exposure levels in the form of a thermograph and 5-bar display for easy monitoring of gamut errors.
5 Bar Display
Shows Y, R, G, B levels as well Y+C levels allowig easy RGB and composite gamut monitoring. Levels are user settable. Instrument logs timecode referenced errors.
It is necessary to monitor not only Y, PB, Pr but also RGB levels during production. The reasons are explained below in the section titled: What Are Gamut Errors?.
Gamut error detection is essential otherwise production material will most likely not be useable. In addition to the 5-Bar display, a on-picture gamut error indication facilitates quick determination of gamut levels and helps in eliminating the problem (see What Are Gamut Errors? below for an example on how the on-picture gamut display can be used to adjust your camera for the optimum take).
On-Picture Gamut Display (Bottom-Right) : Shows where gamut violation is occurring. Reducing the camera’s Matrix Gain adjustment (set at MAX) will cause the gamut indication to disappear. A great way of setting your camera to produce the maximum amount of possible color without violating gamut conditions.
What are Gamut Errors?
Understanding Gamut Errors : Our cameras sensors pick up information in RGB form. Our monitors and even our home TV systems also display the information on their display in RGB form. However, our studios and transmission systems use Y, Pb, Pr in order to process our work. There are several reasons that we convert our RGB information to Y, Pb, Pr for processing. Y, Pb, Pr reduces unwanted color detail and effectively dedicates more bandwidth to the luminance channel where detail is best appreciated by the audience. Also, it is easier and less demanding to build systems processing Y, Pb, Pr.
It is this conversion issue from RGB to Y,Pb,Pr (and visa-versa) that makes it imperative to monitor not only Y,Pb,Pr but also the RGB channels. As it works out, there are legal value combinations in Y,Pb,Pr that result in illegal RGB values (over or under range). This results in a particular color (any combination of RGB) to be clipped either at the lows or highlights and creates serious unwanted artifacts.
Take a look at the shot above. The bottom-left quadrant shows the real
picture. A CINEZONE view (top-left) shows levels in false colors. The 5-Bar display (bottom-right) shows luminance (first bar) is a bit overlevel (clipping at the highlights). It also depicts RED (4th bar) to be way to hot (clipped). The top-right quadrant shows where the luminance (Y) and RED channel are being violated on the picture. Small gamut errors in specular areas and at the edges of highlights may be acceptable for artistic purposes but should be avoided as they cannot be corrected/adjusted in post production. The screens above indicate that the RED channel is way to hot in this shot and it is effecting the majority of the image.
Want to know how we actually manage to take the shot and make it legal? Read below:
How We Took the Shot:
By using the camera’s built in signal processor we were able to take this shot while maximizing the performance of our camera (JVC-250) for the given circumstances. HERE’s how we fixed it : We cut the exposure a fair amount until the gamut error disappeared but this made the image way too dark. We also applied a knee adjustment at 80%; this helped limit large luminance excursions (reflections). We then applied a Black Stretch essentially modifying the toe adjustment of the camera and raising the low tones to midrange (that gave us a bit more brightness otherwise the shot was too dark from stopping down too far). At the same time, we reduced the black pedestal level (which gave us richer shadows in this very bright environment). Finally, we reduced the color matrix (gain only) a bit until we saw the on-picture gamut display (top right) indicate the problem only at the edge of highlights.