SW Digital resolution

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Rookie
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Joined: Sep 27 1999

Hello!
Just a bit curious about the actual resolution of the digitally "filmed" Attack of The Clones. When watching the film in the theatre the image seemed rather blurry.

As far as I have learned the vertical resolution of the HD cameras used was only 1084 lines(!) Less than double the resolution of DV! Could this be correct?

Furthermore, the film was shot in a 16:9 format and then cropped top&bottom to make it Cinemascope. This would further degrade the vertical resolution!

Any expert thoughts about this matter?

Alan Roberts at work
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Joined: May 6 1999

Backplates were shot using Sony HDW900 HDCAM. 1920x1080 at 24fps proscan. Those images are subsampled to 1440 pixels by 1080, and the chroma channels are 480 pixels by 1080. The 16:9 images were cropped to cinemascope (2.35:1) resulting in 818 lines.

All the cgi and compositing was done in 1920 by 818, full bandwidth RGB (known as 4:4:4). The print to film was from this 4:4:4 recording. All compositing was done on disc, no tape involved.

Apart from the less than perfect backplates, if it looked soft to you, it was probably down to the film processes or the projector. The cgi images themselves are very sharp.

mbridge
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Joined: Apr 11 2001

Rookie

Sorry this doesn't answer your question, but illustrates Alans point about the quality of projection. I used to work with a colleague who previously was a film grader, and he always complained about the picture being soft and not focused properly, at his local cinema. Try going to a cinema where you know they care about the quality of the projected image, such as the NFT, or an independent arthouse cinema, they are usually better the the multiplexes.

Martin

Alan Roberts at work
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Joined: May 6 1999

But you can believe all the data I gave, I have a secret source of accurate information. All may be revealed after I retire.

mbridge
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Joined: Apr 11 2001

Alan

Sorry I did not mean to question your information, I had wondered how George Lucas had shot Episode 2, and wondered if he had developed his own solution. I look forward to reading your postings after you retire.

Martin

Snake Plissken
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Joined: Sep 17 2000

What is the resolution of 35mm film in comparison with the digital, if you can compare a pixel to a grain? I mean, when scanning a film negative into the computer, what's the standard size - 1920 by 818 doesn't sound a lot.

tom hardwick
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Joined: Apr 8 1999

I'd suspect the quality of the projector lens, its alignment and setup to the screen itself. I've been in many a cinema and noticed the sharp centre and soft edge(s). Of course projector lenses are always working at maximum aperture and they're hinged to allow cleaning of the gate. Just think how we'd react to our cameras having hinged zoom lenses flopping about out front.

tom.

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Joined: Sep 27 1999

quote:Originally posted by Alan Roberts at work:
...if it looked soft to you, it was probably down to the film processes or the projector. The cgi images themselves are very sharp.

Well you're probably right (as always) . However I have now seen the film twice at two different THX certified Theatres, surely at least one of them should have a decent projector?

Alan Roberts at work
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Joined: May 6 1999

Projection systems are extremely variable in quality.

A recent set of tests was done by an ITU group, to measure the preceived resolution in cinemas. They shot a standard test card on 35mm neg. Densitometer measurements showed that resolution limited at about 3500 lines/height. By the time they'd printed it to pos, and then to interneg and release print (that's the normal route for cinema), it was down to around 1300l/h by the densitometer. But, when projected, no-one in the subjective testing panel could resolve more than 800l/h. And this was done in several new cinemas across the US.

If you do the sums you'll see that you can't rersolve much more than that anyway. Human vision is limited to about 3 seconds of arc, smaller than that and it's not resolvable. It's all spherical geometry from there.

Alan Roberts at work
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Joined: May 6 1999

Probable error in my last message, I reckon human vision limit's 3 minutes, not 3 seconds. Here's how to measure your own vision and do the sums for what's required of a display system:

Take a ruler, marked in mm. I like the transparent ones with black engraved marks, because the mm lines are almost exactly 0.5mm wide, so the markings have 50% duty factor. Tape this ruler to a window or any source of back-light, against the sky is good. Get close enough to be able to read the markings, and steadily back away until you can't quite make out the mm markings any more. Get someone else to measure the distance from your eyes to the ruler. In my case, that was about 1.4 metres.

So, you now know the limiting resolution of your eyes. To estimate what a cinema must offer you, you need to know how big the screen is and how far away you are. Modern cinemas put the audience between 0.7 and 2 times picture height, and it's this ratio that you need to know.

Lets assume you are viewing from 1 times picture height. My measurement of 1.4 metres distance must mean I can simulate the cinema with a screen of 1.4 metres height. So, when viewing from 1 times picture height, my eyes limit at 1400 lines/picture height. And viewing from 3 time picture height, I limit at just under 500 lines. I can confirm that just by positioning myself at 3 times the height of a tv set, when the lines aren't clear any more. This last one's a bit obscured by interlace, but let's not get too involved in that here.

So, although 35mm neg can record 3500 lines/image height, there's no way you'll ever see up to that limit. Partly because you're never close enough to the neg, and partly because the printing and projection process knock an awful lot of it out before it gets to you, the viewer.

Hope that helps a bit.