Most everyone can agree that 4K footage downscaled to 1080p looks great. Even cameras that don't shoot 4K are often oversampling in order to output a clean 1080p file. However, when you're shooting 4K or 5K on a RED camera and you're outputting a 1080p file in post, it turns out not all downscaling is created equal. While RED has just released a tutorial on how to export footage from their grading software, REDCINE-X, they barely mention the Software Scaling setting, and so I did some testing myself:
First, here's RED's exporting tutorial:
The other day DP Timur Civan dropped by my Brooklyn apartment with a RED EPIC, as he's a vintage glass aficionado and he wanted to test out my 35 year-old Canon K35 lenses. You might recognize this back yard from my Kickstarter video. This time, however, we were just messing around and checking out some of the crazy purple-pink flares you can get on these old lenses thanks to their slightly radioactive thorium coating ((According to Wikipedia, "Natural thorium decays very slowly compared to many other radioactive materials, and the alpha radiation emitted cannot penetrate human skin meaning owning and handling small amounts of thorium, such as a gas mantle, is considered safe." That's good to know.)). This is handheld, ungraded stuff, and the lenses are often stopped down to the point where we're dealing with a very deep depth-of-field (no matte box, no ND), but you can still see these unique flares (especially at the end):
Brilliant, I know. We're up for an Oscar, obviously. While outputting and downscaling the 5K files in REDCINE-X, I noticed a Software Scaling sharpness setting, which is undocumented in REDCINE, barely mentioned in the tutorial video, and also rarely mentioned on REDUSER (I posted about it here). As you can see at right there are plenty of downscaling algorithms and it's hard to know which is best. I did an impromptu comparison between Mitchell (the default) and Lanczos3 and exported it as an animated .gif, blown up to 300%. Here it is, keep an eye on the sandal's "adidas" lettering:
Lanczos3 is the sharper one, but more sharpness can bring with it more noise and artifacting. Lanczos3, however, is a "sharper" not "sharpest" setting so it may work in many situations. For a company that espouses sharpness so often, I was surprised that RED hadn't documented these differences at all. However, I got a definitive answer from Local 600 DIT Thomas Wong when he recommended the solution RED would also likely recommend: "use a RED ROCKET." There are no sharpness options with the Rocket as it is hard-coded, and one must assume that the Rocket's hardware algorithm is better than many of these software options. Still, I found the number of options interesting, and given most of us will be outputting to 1080p even when shooting in 4K, it's something worth experimenting with. If you're a RED shooter and you want the sharpest 1080p output, be sure to try out more than one setting during the export!
Have any other RED shooters experimented with these settings?