Sunday, August 16, 2009

Michael Cioni of LightIron Digital on shooting resolutions for RED

I had the pleasure of working and learning from Michael Cioni of LightIron Digital. He is a valuable resource to the RED community as he has overseen post on hundreds of RED projects.

If you every wondered which resolution is best for your project, here is a breakdown in layman's terms courtesy of Michael.

So here's the skinny-

4K2:1 is no longer an ideal shooting format. My recommendation is not to use it because there is no 2:1 delivery format. 1-2 years ago, 2:1 made more sense because QuadHD wasn't available and 2:1 and was necessary for some early system integration (like real-time Scratch playback). Though I like 2:1 as an aesthtic aspect ratio, it makes for difficult conversions to 1:78 and 1:85.

In my opinion, 4K 16:9 should pretty much only be used for theatrical releases (actual 2K and up). If a RED project goes to HD, you probably want to stick with 4KHD, or QUAD HD. QuadHD is a great format because it is exactly 4x bigger (200%) than 1080p HD. 4K16:9 is actually a bit bigger than QuadHD. When you scale down 4K16:9 to HD, you do not have whole numbers (because you can't divide 4096 by 1920) without remainders. However, if you take Quad HD (3840 by 1920) you get "2" - a whole number with no remainders.

That means you get all sorts of advantages with QuadHD:

• Slightly smaller file sizes
• Faster renders to 1080 (upto 33% faster than 4K16:9)
• Better use of the Proxy Movies in 1080p
• Sharper images at 1080


YES, it is true. When you down sample 4K 16:9 to 1080 or 2k, you get those remainders - those are actually square pixels of one aspect ratio being crammed into another aspect ratio. That means you do not have what is called a "pixel-for-pixel" downsample. When you use QuadHD, you literally eliminate half of the vertical and horizontal pixels, but there is no sub-sapling applied since the numbers are even remainders. This is a great way to do conversions - which is made easy by the fact Red shoots Wavelets (which love to be divisible by 2). That's why you get all those quick and easy 4K, 2K, 1K and 1/2K QT movies so easily - it's literally just doing the division on the fly by 2. The only problem is, when in 4K16:9, the division is not so good with 1920x1080. Where as in Quad HD, you are perfect. The result is a SHARPER image in 1080p from QuadHD vs. 4K16:9. Though it is not a whole lot sharper, it can make a difference for visual effects compositing, rotoscoping and keying. It also makes a difference in very busy wide shots or perhaps shots that suffer from tricky focus situations.

Overall, if you are not doing a 2K or 4K master, there is little to no benefit to shooting 4K 16:9. Period. The only thing I would look out for is that QuadHD is going to push into your lenses a TINY bit- making a 50mm act more like a 55mm. That may be a deal killer for some DPs, but the overall image quality, speed and mobility of the images may be a better trade-off.

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