Using SD Footage in an HD Production
/Using standard definition footage in a high-definition production poses special challenges. But with so much irreplaceable SD footage out there, it's a puzzle producers must solve regularly. We talked with some of our friends on the archive side, including experts from FootageBank, Framepool, Global ImageWorks, INA and NBC News Archives to get their perspective on how they manage client requests for SD footage. Here's what we learned:
Aspect Ratio is the Biggest Hurdle
Most clients these days understand and accept that SD footage will be lower res than HD. However, a more significant obstacle is the size and shape of the SD frame. With an aspect ratio of 4:3, the SD frame is smaller and nearly square, so conforming an SD shot to the larger, more rectangular dimensions of a 16:9 HD frame is the more vexing issue. As Sandrine Sacarrere of INA puts it, "aspect ratio may be the easiest setting to illustrate the differences between 4:3 and 16:9, especially with its consequences on anamorphosis or cropping."
Upscale Options
While these issues are generally understood by clients, our panelists make sure to remind them that SD clips will have to be upscaled. The most common upscaling methods are pillarboxing, wherein the image is scaled up until the top and bottom borders of the SD image align with the HD frame, leaving black space on either side of the image (pillars); cropping; or, in some cases, stretching the images.
Go Native
Most of our panelists agree that it's better to deliver SD footage in its native format and let the clients handle the upscaling work on their own. As Paula Lumbard of FootageBank puts it, "we have found it works best for a client to convert on their end so they have control over what part of the frame is lost, whether it's the top or bottom." Jessica Berman-Bogdan at at Global ImageWorks takes a similar view: "in my experience, most editors/post supervisors want to control SD to HD upconverts so that the look and feel to the footage is consistent with the overall look and feel of the film. I have seen the successful results of following this policy on many a film. Therefore, Global ImageWorks encourages our clients to let us deliver the most native format and for them to do their own upconverts."
Pillarbox, Don't Stretch
If they do perform the upconversion, most of our panelists agree that pillarboxing is the best method and image stretching is not an ideal solution. "The pillarbox process is the right way to upscale as the frames remain intact," says Stephen Bleek of Framepool. "If the clients need a crop to 16:9 full frame he/she can do that afterwards with the up-resed pillarbox version on his/her editing system. This way the client can choose exactly the crop he/she wishes." At NBC, "some clients ask us to up-convert SD footage," says Luis Aristondo, Operations Manager for NBC News Archives. "Most requests are for pillared and very few are for stretched." For Paula Lumbard, image "stretching is not an option. No matter what, the human eye can tell an object is stretched, even a flower let alone a face or animal."
For Best Results, Start with Film
Of all the SD formats, 35mm film offers the best source material for an upconversion. "When it comes to film, 16mm is considered SD and 35mm is considered HD," says to Luis Aristondo at NBC. Stephen Bleek at Framepool puts it this way: "35mm still offers a great resolution, even up to 4K. But some film scans need de-graining in addition to match nowadays guidelines. The resolution of 16mm is too low to get really good HD results. But if you have archival images shot on 16mm it is better than nothing." According to INA, "scanners can transfer 16 mm films in DPX files in SD, HD or 2K. 35 mm can be scanned up to 4K and even 8K, but it is still rare. We consider 2K as the good resolution for remastering our collection. But 4K is on its way..."
Proactive Upscaling
Consequently, most of our panelists do some proactive upscaling of film elements to HD. For example, Framepool "is constantly scanning archival film reels to HD formats." At NBC News, "new content being digitized by the network archives department from tape is being ingested as up-converted pillared."
There Are No Magic Tools
At the moment, there do not appear to be any real alternative ways to scale up SD footage so that no data is lost, cropped or and the image is not stretched. As Stephen Bleek at Framepool puts it, "there are no magic tools that can produce detailed and realistic looking additional resolution. But in some cases an upres can look quite okay. Especially close-ups since they contain fewer details than wide shots."