General > General Technical Chat
An expensive TV is a poor investment, and people spend FAR too much on them
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tooki:

--- Quote from: bw2341 on February 10, 2022, 01:14:39 am ---There's a high end LED video wall at my local Apple Store and I was able to walk right up to it. Very impressive. The light modifiers blend the LEDs together very well so I was not able to discern individual LEDs. Even though the display faces the outside glass curtain wall, there was plenty of contrast in the image. They were using it for the in-store teaching sessions. This was in The Before Times, of course.

--- End quote ---
The one at an Apple Store is also the only top-quality one I’ve seen up close, and I agree that they look fantastic!



--- Quote from: bw2341 on February 10, 2022, 01:31:14 am ---
--- Quote from: tooki on February 09, 2022, 09:44:36 pm ---Projection varies wildly, depending on the type of screen. High-gain screens have distracting reflection patterns. :/

--- End quote ---

This is probably an artifact of 3D capable theatre screens. Most theatres use circular polarization optics to project the separate left and right eye images. The screen material has to retain the polarization of the incident light when reflecting it back to the viewer. Otherwise, there will be crosstalk between the left and right eye images. The screen has to be high gain so that the image is acceptably bright through the 3D glasses.

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Nope. High-gain screens have been used for decades, they have nothing to do with 3D. They use surface structures that prevent light from scattering off-angle as waste light. But the disadvantage is that it reduces viewing angle. (Fun fact 1: top-quality cinema screens use surfaces so delicate that touching it ruins it. Fun fact 2: cinema screens are acoustically transparent because they have the front speakers behind them.)

You’re probably correct about an incompatible screen interfering with polarization 3D, but I don’t know for a fact.
BrianHG:

--- Quote from: bw2341 on February 10, 2022, 01:31:14 am ---This is probably an artifact of 3D capable theatre screens.

--- End quote ---
Aww, they are still pushing that crap.
tom66:

--- Quote from: BrianHG on February 10, 2022, 08:30:30 am ---
--- Quote from: bw2341 on February 10, 2022, 01:31:14 am ---This is probably an artifact of 3D capable theatre screens.

--- End quote ---
Aww, they are still pushing that crap.

--- End quote ---

Films are still made and shown in 3D, though it is becoming less common.   3D TV/home cinema is basically dead.

The last time I saw a 3D film in the cinema was 2014 and it made me quite unwell.   
Siwastaja:

--- Quote from: tooki on February 09, 2022, 09:56:06 pm ---But with the comparatively low contrast of projection screens it barely matters.

--- End quote ---

Yes, what limits dynamic range in projection setting is the white (or silvery) screen reflect the light on the walls, ceiling, floor, even the people, and this light ends up back on the screen; this can't be avoided even if the projector optics are perfect!

The whole theater and all its materials could be painted matte black, but somehow consumers don't want that either.

A screen of a "large TV" can be made nearly black, meaning it reflects very little light coming in from the front, solving this problem.
tom66:
Not to mention despite the power of a projection bulb (3-10 kW in current cinemas) it's still a relatively small amount of light dispersed over a large screen.

A huge LED matrix could achieve, say, 500W/m^2 without breaking too much of a sweat, especially if it had thermal ABL (brightness limited by temperature or average power, rather than just peak power.)   This would massively improve the apparent contrast ratio.  I could see some of these screens pulling 10-20kW for certain scenes.

(Maybe cinemas will start to prefer darker films, saving them money on the electricity bill and the maintenance of the panel.)

I do worry we'll see films with lots of dead pixels/modules though.  I've seen a few large outdoor matrices with entire blocks of ~32x32 pixels showing garbage.
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