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Author Topic: Projecting the Color Black
Paul Finn
Film Handler

Posts: 24
From: Bay City, MI
Registered: Jan 2019


 - posted 06-12-2019 07:42 AM      Profile for Paul Finn   Email Paul Finn   Send New Private Message       Edit/Delete Post 
Projecting black from a film frame creates an absence-of-light area in the projected image for the desired black area in the picture. Is an absence-of-light area also created from the projector in a digital picture for black scenes? Or, do DMDs or other imagers create black in a digital picture by another method (than absence-of-light) that is projected as part of the color/light picture parts?

Thanks,Paul Finn

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Carsten Kurz
Film God

Posts: 4115
From: Cologne, NRW, Germany
Registered: Aug 2009


 - posted 06-12-2019 07:50 AM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
Essentially, it is the same, however, most digital projectors do not manage to create the same amount of 'absence of light'. A black frame in film is usually not perfectly black as well - it has a limited maximum density, and the frame may show some minor scratches, holes, etc. as well. However, in general, film black is blacker than digital projector black.

In reality, it is a bit more complex. Modern digital projectors may cheat using variable irises, light source dimming, a dowser, whatever. However, most of that is not available in real DCI compliant digital cinema projectors.

- Carsten

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Marcel Birgelen
Film God

Posts: 2958
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012


 - posted 06-12-2019 08:43 AM      Profile for Marcel Birgelen   Email Marcel Birgelen   Send New Private Message       Edit/Delete Post 
The very definition of black is the absence of light. A perfect black surface is a surface that reflects no (visible) light at all. Such a surface is currently only hypothetical, although we're able to make material that can come close nowadays.

DLP projectors essentially dump all unused light into a heat-sink and LCoS based projectors try to block all the unused light right at the imager itself. Those processes aren't perfect and some light eventually leaks out of the light engine, into the lens and onto the screen. That's why in current standard DCI, black is more like a constant, deep grey.

Like Carsten already mentioned, none of the current DCI compliant machines use tricks like irises or dynamic light sources, which can help to increase on/off contrast in certain scenes, but come with other problems. It's because of those problems, it's currently not certified to be used for DCI.

There is one noticeable exception here and that's the Dolby Vision setup (used almost exclusively in Dolby Cinema), which most likely uses something like a segmented integrator rod construction, where each segment can be individually dimmed. This trick is comparable to what can be achieved with local dimming, used by many modern LCD/TFT based screens, where the backlight consists not only out of a single light source, but many smaller light-zones which can be individually controlled.

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Bobby Henderson
"Ask me about Trajan."

Posts: 10811
From: Lawton, OK, USA
Registered: Apr 2001


 - posted 06-12-2019 10:09 AM      Profile for Bobby Henderson   Email Bobby Henderson   Send New Private Message       Edit/Delete Post 
Laser projection works better at creating a deep black than traditional Xenon-based DLP digital projection. One of the Dolby Cinema trailers has a kind of funny tag line at the end, written in small type over a black screen, "the projector is still on."

LED jumbotron displays can easily create a true black since it's only a matter of turning off specific LEDs in the display. OLED TV sets at home work the same way, each pixel is specifically illuminated. Due to high cost and other technical challenges I think it's going to take at least another decade of development before we see LED screens going into commercial theaters on any sort of widespread basis.

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