Following our interview with Pixmondo's VFX supervisor Ben Grossman – who won an Oscar for Hugo – about how to use stereoscopic 3D to subtly affect viewers emotions, we wanted to find out how other creative techniques are being used with the new medium. We caught up with colourist Dado Valentic of Mytherapy, who worked on many early IMAX 3D projects and mastered StreetDance 3D, the first British stereo 3D film, to find out how grading can be used artfully in 3D.
Dado says that there are a few technical challenges that need to be overcome first when working with 3D footage. The first is that because of the glasses audiences wear, 3D films and TV shows need to be a lot brighter than 2D productions. “You have to take parts of the image that will disappear into the darkness and make them visible again without creating a distortion,” he says.
You also have to adjust 3D footage differently, depending on whether you’re working for cinema or TV, as bigger screens give audiences a much larger sense of depth. 3D TVs are brighter, allowing more scope for adjusting the overall look of a shot, but you can’t use a correction technique called ‘floating windows’, as this only works when the audiences are in darkness.
Dado says that some traditional techniques for increasing the perception of depth in 2D footage also enhance stereo clips. “Warmth of colour doesn’t affect depth perception but saturation does,” he says. “When you look at an object, the further away it is from you, the lower the colour intensity because the light reflected from the object to your eyes is less intense. Most 3D movies are pretty full on when it comes to colour. Look at the on-set stills from The Hobbit, their colour is so exaggerated because [when you’re grading] you want to strong tones to help with the effect of depth.”
Below Dado takes us through grading a shot from Jet Set Films using Blackmagic Design's DaVinci Resolve colour grading software. For each step we've placed the left eye frame first and the right eye second.
"We started with a RAW image captured with a RED One camera."
"In the first pass we have fixed following issues: colour, exposure and contrast discrepancies between left and right eye. This is due to the fact that 3D camera rigs are using two cameras, which always have some colour discrepancy between them. You're also shooting through a mirror that colourises one eye with green tint and one eye slightly magenta.
"There's a vertical and horizontal misalignment present that has been corrected. We have also fixed a polarisation issue on the front window of the bus in the background. Then we have enhanced the BMX rider by applying a mask and slightly brightening him up as he is on the convergence plane."
"Once we have fixed all the technical issues, we moved on to creative colour grading. Here we have applied a look that slightly exaggerates saturation to compensate for the loss during 3D projection."