This is a bit more of an in-depth article than I've written before. I hope you enjoy it.

I've been researching digital video/cinema partly because I'm curious and partly because I want to build a really kick ass digital home theatre at home. Obviously it has to be 1080p HD. But there's a digital cinema company in Waterloo, Christie Digital, that donated a very high end projector to the Accelerator Centre, with more than 1080p resolution. And, I enjoy reading about how movies are made, and I started to realize that film has a higher practical resolution than 1080p.

A review of Curse of the Were Rabbit in American Cinematographer mentions that they scanned their film at "6K" resolution. That's 6000 pixels wide, three times the width of 1080p, equivalent to an 18 megapixel camera photo for each frame. But can you go higher? Apparently, yes. According to this article filmmakers consider 16K to be adequate. 16K! Awesome!

To put in perspective, the storage required to store that is 21GB per second. It kind of starts to sound like gigapixel imaging, although realistically (a) your eyes can't possibly see all the detail in a gigapixel image anyway and (b) film cannot possibly get the same detail level as a proper gigapixel image.

To go to the perfect digital cinema system, though, resolution alone is not enough. You also need to be able to reproduce, in each pixel, the full dynamic range of light that exists in the real world.

HDR photography is a lame attempt to achieve this. It works like this: you take several photos at different f-stops, recording the brights, the mids, and the darks onto separate digital photos. Then, you use software to selectively compose these multiple photos into a single image. What you get is something that looks completely artificial but allows you to see details in the brights and the shadows that would otherwise be washed out.

More advanced HDR capture uses a single sensor that can simultaneously capture the wide dynamic range of the human eye. Normal digital sensors only record at a bit depth of 8 bits of luminescence per pixel. Waterloo digital cinema company Dalsa has a 4K "Origin" camera that records at 16 bits per pixel depth. That's much closer to the actual perceptive capabilities of the human eye.

You could fix the lame-ness if you could find a way to then display at that bit depth. But no commercial displays can do that yet. Even hyped products like Sony's 1 million to 1 ratio OLED cannot actually come close to the brightness of the real world, because the maximum brightness of the display is only about 600 nits (cd/m²).

Comparatively speaking, maximum direct sunlight is 100,000 lux. Lux and nits are related (oddly enough) by a factor of pi, so 1 nit is equal to 3.14 lux, if the surface being illuminated is perfectly white. (Lux is light cast on something, nits are light cast by something.) 600 nits is nowhere near bright enough to match the daylight it's trying to represent.

Dolby recently bought some interesting technology called BrightSide which can display at 3000 nits, equivalent to decent daylight. You can see the effect in photos that show the old vs. new technology on a side by side basis. There's an image below with an LCD TV on the left and a BrightSide demo on the right from an article by Geoff Richards.





To conclude. 1080p is pretty damned good for now, equivalent to 2K cinema. I'm probably going to aim for whatever is the brightest screen I can get, but I'll definitely be looking forward to seeing something like BrightSide display technology to be available as soon as possible, because I think it will make a huge difference to the viewing experience—make the picture much more like the real world.

[Update: I was thinking that 16K might not actually be enough to ultimately satisfy the human eye. 16K = about 100 megapixels. But these calculations about the human eye make me think that would probably be enough actually. It would really be a question about how much field of vision you want to fill, and the more you fill, the more the eye has to move around to see it all. So 16K would probably be satisfactory for a movie where you would expect to have a reasonably focused field of attention.]

[Update 2: Good god, I've just discovered that there's also a framerate issue. What happens if you are showing a "24p" (24 frames per second) movie on a display that always has to work at 30ftp, like any NTSC TV? They do something called "pulldown" (repeat some frames) or play other tricks. I don't completely understand what these tricks accomplish (3:2 or 5:5 pulldown?) or what exactly the "film look" is (something to do with shutters?), but it seems to me that if you want to have a proper home cinema you should display what the moviemaker intended you to see. It would appear that I'll need to pay attention to frame rate issues to make sure I get that.]