American Cinematographer - December 2021 - 65

AMERICAN CINEMATOGRAPHER ASCMAG.COM
Top: The top row of fabric and produce is lit by LED walls and the bottom row by LED cinema lights. The lack of
yellow wavelengths on the top row affect proper color representation of the bell peppers, and the cabbage is
an example of a lack of deep blue. These items skew toward red, specifically, because of the high power and
saturation of the red LEDs. Bottom: A view of the test setup.
Walls and Movie Lights
The color-fidelity issues explored
in this test exist essentially across
the board in LED-volume environments.
This is due in large part to
that fact that using LED walls as a
lighting source was not an intended
application when the technology
was developed, as the panels that
comprise these walls are designed
to be viewed directly. Initially
offered for concerts, billboards and
large-screen presentations, the
panels' most important attributes
are therefore the direct-view color
and spectral response. For this
reason, manufacturers have been
choosing LED emitters based on
RGB patterns optimized for the
color space of display standards,
such as Rec 709, DCI-P3 and HDR.
By contrast, many professional
starting with a blank greenscreen
- but you must be aware of the
reduced color gamut, and manage
it through a combination of adding
cinema lighting (see sidebar, this
page), toning down highly saturated
primaries in the imagery on the
off-camera panels, careful selection
of colors with the art department,
and color correcting in post. "
Light meters such as the Sekonic
C-800 and C-7000 spectrometers
are very helpful in volume work, Kief
adds, " especially for matching cinema
light to volume light, using XY
measurements. " Additionally, once
the full-spectrum analysis has been
completed, " the readings can be
helpful to predict where problems
are likely to show up in skin tone
and color shifts on camera. "
Emerging Gear
Some LED-wall-specific lighting-supplement
solutions are
already appearing, including
Sumolight's Sumosky - a portable,
adjustable LED wall for
off-camera supplemental light.
The unit is essentially a large
sheet of translucent material
backed with proportionately
spaced LED bars; it can be fed
pixel-mapped video signals like
a standard LED wall, but it also
includes white-light LED bulbs for
simulated full-spectrum response
up to 16 bits per channel.
Another approach is a hybrid
LED instruments for movie and TV
lighting are designed to reproduce
the best spectral distribution
across the color spectrum. Says
Craig Kief, ASC, " The white-light
LEDs have improved dramatically,
as the manufacturers have focused
on increasing color rendition over
the last decade through improved
phosphor recipes in the emitters,
and by adding additional emitters
- such as RGB, and more recently
amber, cyan, lime green and others
to fill in the spectrum. "
DECEMBER 2021 / 65
BOTTOM PHOTO BY MARK DOERING-POWELL, ASC.

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American Cinematographer - December 2021

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