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Alexa footage viewing on DLP and laptop


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#1 Eric Lin

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Posted 13 July 2012 - 03:04 PM

Hi all. I'm a DP that is prepping an Alexa feature. I've shot small screen stuff with the Alexa but finally had a chance to do a real color corrected test in Deluxe's color timing suite projected via DLP. We color timed some tests I shot using Prores 4444 to SxS cards in LogC.

I was floored by how good the Alexa ProRes footage at 3200 looked! There wasn't as much apparent grain in the image than I expected. Here is where I got a bit curious. On a regular computer monitor (laptop or even my 23" mac HD monitor), the Pro Res files of footage shot at 3200 are very grainy with and without the LUTs applied. You can really see the noise on a smaller screen but not so much off the DLP which is not what I expected in terms of the noise of the image. I certainly don't expect the two to look similar but just in terms of noise in the high ISO footage, I expected it to be much more apparent when projected.

I expected the grain to be more apparent when projected simply because the footage is being enlarged. But it really wasn't the case. Blacks were fairly solid. You certainly saw an increase in noise but it wasn't nearly as close as grainy as what I was seeing on my computer monitors.

They assured me no noise reduction was being applied. Is it just the limited color and contrast range of the LCD monitors that make that grain so much more apparent? I'd love to hear anyone's insights.

Thanks so much!

Best,
Eric Lin
NYC
DP
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#2 Eric Lin

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Posted 16 July 2012 - 07:45 AM

For future reference from my colorist friend if anyone is curious:

- DLP projectors typically use a rendering technique called error diffusion dithering, which enhances color rendering, but results in shades being averaged over multiple on-screen pixels. This can mask single-pixel details when there are only small differences in shade between adjacent pixels, as is typically the case with image noise. LCD screens, in contrast, will typically display an input signal pixel-for-pixel.
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#3 Phil Rhodes

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Posted 16 July 2012 - 10:10 AM

Only very cheap DLPs and TFTs do temporal dithering like that. I'm astonished you found it on one in a Deluxe facility. Certainly not all TFTs are free of it; they can and do use exactly the same techniques, although a decent one won't.
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