Sony’s Head of Business Development – 3D, 4K & Sports, Mark Grinyer, provides a word of caution before any live production leaps into the wonderful world of 4K.
Single-chip vs Depth of Field (Focus depth)
“Before you start thinking about 4K there’s a serious consideration to take into account when it comes to 4K cameras versus ‘normal’ cameras,” he says. “4K cameras are single-chip models, whereas broadcast cameras have 3CCD blocks (Red, Green and Blue) and the image is more sensitive to depth of field, which is perfect for live productions such as Top Gear. It’s much more straightforward to get a far greater depth of field with a broadcast camera, compared to a 4K camera.”
Depth of field is related to the amount of light and the control of the iris, and, says Grinyer, “some learning needs to be done around single sensor cameras” to create a similar effect. “The camera operator and the producer/director needs to be aware of what to do [with a single sensor 4K camera] in terms of managing lenses, focus and exposure, to create a similar depth of field to a broadcast camera.”
It’s certainly not impossible to emulate the depth of field of a three-chip broadcast camera with the latest 4K cameras, though it’s just a skill that will need to be learned.
“If you were shooting with a single-chip HD camera you’d struggle to get a look as good as with a three-chip camera,” explains Grinyer. “But 4K cameras are a lot more sensitive, providing more F-stops, so you can adjust the exposure, iris, lenses and other tools available on the camera to adjust the imagery.
Once any issues relating to creating an appropriate depth-of-field have been addressed, there are huge potential advantages in opting for a 4K camera over an HD model, even if you’re delivering in HD.
“Anything shot in 4K and down-converted is going to be better than HD, which is partly down to the noise ceiling and signal,” explains Grinyer. “The clearer signal to transmission, the clearer signal you get at home. You get a better picture as there’s a lot more data to down-convert compared to a standard HD image.”
Just remember that 4K eats up 4 times the amount of data, creates much larger files sizes (4x) and will have an effect on the speed of any post production suite and your production deadlines. And 8K, on the way will be (8x) … the stuff of cinema.
At the end of the day, how is that video going to be used? On desktops and mobiles mainly? If that’s the case, it’s not necessarily worth the extra time and cost to produce in 4k when it’s not going to be seen. 4K for desktops and tablets – no.
For commercials and large screen features – yes.