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» Film-Tech Forum   » Operations   » Ground Level   » Projecting the Color Black

   
Author Topic: Projecting the Color Black
Paul Finn
Film Handler

Posts: 30
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: 4137
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: 2981
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: 10820
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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William Kucharski
Expert Film Handler

Posts: 229
From: Louisville, Colorado, United States of America
Registered: Oct 2012


 - posted 06-24-2019 02:50 AM      Profile for William Kucharski   Email William Kucharski   Send New Private Message       Edit/Delete Post 
quote: Bobby Henderson
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."
Which always makes me a bit sad, as obviously it's intended to be white letters on a pure black screen, but instead it's always a pure black screen with lit corners from the floor exit lighting plus often lit top corners from other low-level lighting around the theater. [Frown]

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Marcel Birgelen
Film God

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From: Maastricht, Limburg, Netherlands
Registered: Feb 2012


 - posted 06-24-2019 05:29 AM      Profile for Marcel Birgelen   Email Marcel Birgelen   Send New Private Message       Edit/Delete Post 
Try to see it in a country where AMC doesn't have exclusivity of the Dolby Cinema concept. [Wink]

If it is done properly, it is pretty stunning, compared to what we've become used to be "black" in DCI nowadays.

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Justin Hamaker
Film God

Posts: 2199
From: Lakeport, CA USA
Registered: Jan 2004


 - posted 06-24-2019 04:30 PM      Profile for Justin Hamaker   Author's Homepage   Email Justin Hamaker   Send New Private Message       Edit/Delete Post 
I understand that black is actually just the absence of light. But this means the areas of the screen which are black are actually white (or silver). When do we perceive them as black? Is it because of the proximity to other areas where are lit up?

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Sean McKinnon
Phenomenal Film Handler

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From: Peabody Massachusetts
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 - posted 06-24-2019 04:40 PM      Profile for Sean McKinnon   Author's Homepage   Email Sean McKinnon   Send New Private Message       Edit/Delete Post 
The projection screen appears white because it is reflecting light back at a minimum of a 1:1 ratio (unless its a high contrast or grey screen which will reflect light back at less than 1:1 and is often referred to as a "grey" screen) so when the room is dark and there is no light being reflected back to you the screen appears to be black.

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Jim Cassedy
Phenomenal Film Handler

Posts: 1614
From: San Francisco, CA
Registered: Dec 2006


 - posted 06-24-2019 06:30 PM      Profile for Jim Cassedy   Email Jim Cassedy   Send New Private Message       Edit/Delete Post 
quote: Bobby Henderson
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."

When working at Dolby's screening room in San Francisco, they usually had
me run a short Dolby Vision™ intro/demo 'sizzle reel' before whatever else
they were screening. At the end it fades to black. (and I mean BLACK !! )

But if whatever clip that followed it was not in D-Vision, the jump in black
level as it switched from D-V™ BLACK to plain old DCP black was quite jarring.
Almost like night & day, no pun intended!

The effect even more pronounced due to the fact that their auditorium is almost
totally dark, and great care has been taken to keep whatever safety lighting was
necessary off the screen.

Since it's a manually run booth, with a fairly large viewing port, it's necessary to
work almost totally in the dark, the only illumination coming from the monitor
screens & Crestron system control panels. - - but the image quality is AMAZING.

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Bobby Henderson
"Ask me about Trajan."

Posts: 10820
From: Lawton, OK, USA
Registered: Apr 2001


 - posted 06-24-2019 10:01 PM      Profile for Bobby Henderson   Email Bobby Henderson   Send New Private Message       Edit/Delete Post 
I wish some theater chains, beside only AMC, would (or could) install Dolby Cinema systems. I don't know what kind of deal Dolby has in place with AMC, but I think it sucks for AMC to be the only outlet for Dolby Cinema in the United States. I think it's possible for other theater chains to do a better job with the concept.

Compounding the problem further, it looks like AMC has pumped the brakes on any new Dolby Cinema @ AMC installations. Perhaps that has something to do with the debt level of AMC and its Chinese parent company, Wanda. AMC used to have a list of Dolby Cinema screens on its web site, along with a "coming soon" list of upcoming new screen installations. That page is gone. Dolby no longer has the interactive map showing theater locations with Dolby Atmos or Dolby Cinema. They do have a text-based listing of Dolby Cinema locations.

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Mark J. Marshall
Film God

Posts: 3188
From: New Castle, DE, USA
Registered: Aug 2002


 - posted 06-25-2019 11:22 AM      Profile for Mark J. Marshall     Send New Private Message       Edit/Delete Post 
For what it's worth, whenever we projected a film on Kodak's Vision Premier stock, it looked like the projector shut off when it went from our Feature Presentation snipe to the feature itself.

Some IB prints of cartoons I projected that had black on the picture (Lucy's hair in Charlie Brown for example) often looked like there were giant holes in the screen.

There's black and then there's blacker-than-black.

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