Cinematographer Russell Carpenter, ASC, hadn't really seen much in the way of digitally-shot features that inspired him until he caught Mel Gibson's Apocalypto. Shot with the Panavision Genesis camera by Dean Semler, ASC, the film impressed Carpenter as looking entirely cinematic and devoid of some of the more "video-y" attributes he'd perceived in other features shot in HD. So while preparing the feature 21, Carpenter decided to investigate the Genesis, primarily for its reputed ability to see deep into shadows—an attribute that could be particularly useful for the significant portion of 21 set inside Las Vegas casinos.

Based on a true story, 21, directed by Robert Luketic, follows an MIT math professor (Kevin Spacey) and a group of particularly brilliant students (including actors Jim Sturgess and Kate Bosworth) as they use card-counting techniques to beat the odds at a number of Las Vegas casinos. Carpenter liked the idea of having to only minimally augment the practicals inside the casinos, and he was also attracted to the immediacy of shooting electronically and being able to confirm how lighting, color and focus would look right there on set.

"We wanted to shoot wide open on very long lenses," Carpenter says. "We shot a lot of the action at the card tables with a 400mm lens T-2.8. I wanted everything to be blurry behind the actors' heads so you could just see those unnatural colors of the casinos' lights behind them. I think it gave things more of a sense of energy than you'd have if you saw solid objects in the background. It's not always possible in those conditions to hold the subject in focus, but with the monitor I always knew if we had it or not."

Prior to commencing principal photography, Carpenter and Digital Imaging Technician Doug DeGrazzio shot tests with the Genesis and filmed them out. Carpenter determined that some of that deep shadow detail that the camera's imager picked up could disappear by the final print stage. This meant that he'd have to either boost the gain—"A look I didn't care for," he notes—or fill the shadows a bit more than he'd initially thought he'd have to. He worked with DeGrazzio using the Genesis Gamma Display to slightly alter the characteristics of the default Panalog LUT by applying a curve that crushed the blacks a bit on the display, which, in turn, made Carpenter add a bit of extra light in the shadows to make sure there would be enough information on the tape. Carpenter observes that the Genesis imagery still held more shadow detail than he'd have gotten using his favorite film emulsion—Kodak's 5218 500T—though the difference was less pronounced than he'd initially hoped.

This fine-tuning was stored as adjustment curves, which were subsequently used in the grading process. The "looks" were also added as LUTs to the on-set monitor and later used as reference during the final color-correction stage. Once Carpenter and DeGrazzio had arrived at a "look," they stuck to it for most of the show, "painting" it a bit warm for some scenes in Vegas and biasing it on the cooler side for some of the Boston portions.

The curves were stored on CD and sent each day with the HD tapes to Bobby Hatfield, who worked with Semler on Apocalypto, dealing with the creation and projection of Genesis dailies. Hatfield would combine the corrections to the HD signal to create "baked-in" dailies so that everyone involved could see the images with the "look" already applied.

During the final grading at Technicolor, Colorist Stephen Nakamura used the curve information as a guide and then worked with Carpenter to fine-tune 21's look. The cinematographer, who has taken a lot of film negative through the DI process, notes that the options in the suite were somewhat less expansive than what he was used to with film, though there was, he adds, "more than I'd expected. A film negative is a treasure trove of information. You can take it so many different ways. But I was happy with what I could do with the Genesis images. I set the look I wanted on set and I never really had to take anything very far from that."