The Blackmagic URSA Mini Pro 12K uses a different sensor design than most other cinema cameras. Why is this important for filmmakers?
The Blackmagic URSA Mini Pro 12K offers, in addition to its absolutely breathtakingly high resolution (12K, so many Ks) and an excellent dynamic range of 14 f-stops, also a completely new sensor design, a symmetrical sensor layout that no other cinema camera offers.
While sensor design may seem a bit obscure and irrelevant to most directors and producers (and even many DPs), there are some really useful uses of this design that anyone who considers themselves a filmmaker should understand.
What is symmetrical sensor layout and why is it important for filmmakers?
The first thing you should understand is what sensor color layout most other cinema cameras use Bayer array.
The Bayer array was invented by Bryce Bayer at Kodak in the 1970s (many forget how crucial Kodak was in developing digital camera technology). The Bayer array uses a pattern that has roughly twice as many green senses (sensor pixels as opposed to image pixels, which we see in the last picture).
Bayer footage must be debayered in order to be converted into usable footage. Virtually everything you’ve seen on a big screen in the past decade has gone through a debayering algorithm to create the final picture.
Bayer sensors are wonderful. If you’ve ever liked something captured with a RED, Alexa, Sony VENICE, Canon, Sony Alpha, or earlier Blackmagic camera, you’ve seen debayered footage. However, there are limitations, particularly in relation to the computing power required to process the footage. This processing often means that you need to immerse yourself in a smaller part of a sensor to shoot at high speed. This requirement also means that you need a more powerful system in post-production to handle the footage as well.
In addition to the required horsepower, the debayering is not perfect. It uses complicated math to convert images taken with a Bayer sensor into full color images, and there are always artifacts in the process.
These artifacts are usually not visible if you oversample (e.g. shoot 4K for an HD finish), but if you take 4K Bayer images (like on an original RED ONE) and finish them to 4K, you may see Artifacts that prevent the picture from “seeing” full 4K.
You can see fringing or softness where you would expect sharpness. For this reason, most people at Bayer prefer oversampling and photographing an 8K sensor for a 4K finish, as your visible resolution should look good even after debayering.
These artifacts are a natural part of the Bayer process and also affect the symmetrical sensor, but the symmetrical sensor can bypass some of them by massively increasing the resolution.
The readout time of the rolling shutter of the camera is very good with a recording resolution of 12K, but gets even better / faster (fewer rolling shutter artifacts) when you take photos with lower resolutions.
- UMP 12K – 12K — 15.5 ms (full sensor)
- UMP 12K – 12K 2.4-12.3 ms
- UMP 12K – 8K / 4K – 8.5 ms (full sensor)
- UMP 12K – 6K cropping – 7.8 ms
- UMP 12K – 8K 2.4-6.7 ms
- UMP 12K – 4K cropping – 4.2 ms
If you are massively oversampling and want to overcome the demosaicing artifacts, this is where RGBW or symmetrical sensors come into play.
First patented by Kodak in 2007 (Kodak is back), RGBW sensors not only have red, green and blue sensors, but also clear or “white” sensors that do not have a filter. To detect red, green or blue there is actually a small filter (very tiny) on the photo page. If you’ve ever attached a color filter to your camera, you know that it blocks out a lot of light.
With these clear W sensors, these sensors can get better pictures in low light conditions. One of the upper limits of Bayer arrays in terms of resolution is that the low sensitivity to light decreases as the photosites get smaller (since you need higher resolutions). With these clear senses receiving an image in low light, this sensor design challenge is eliminated. It also means you can get that high resolution in a super 35mm sensor instead of using full frame with its added lens and tiny depth of field requirements.
In addition to the higher resolution and better low-light sensitivity, processing also becomes easier as the math is less complicated to take symmetrical images and turn them into a finished, full-color video. Calculations can be done faster by using the same number of inputs and outputting an end result than if twice the number of green pixels had to be compensated for.
Video is no longer available: vimeo.com/manage/videos/470937259/3ebf65f61b
This does not mean that you will not have artifacts with a symmetrical sensor. However, since you can more easily build a symmetrical, high resolution (12K) sensor, you can overcome the artifacts by locking on a lower resolution. If your performance is 8K for theatrical releases, the 12K sensor resolution gives you enough oversampling to produce clean images.
Any resolution camera
These cameras that use RGBW are more like “Every-K” cameras rather than just “12K” cameras.
For example, if you are shooting a commercial or feature film, you can easily record 12K. But what if you are shooting a documentary with hundreds of hours of footage planned? You might want to record 8K, 6K, or even just 4K as the end result will likely be 4K.
Most other cameras require you to immerse yourself in the sensor for a lower resolution. On the Blackmagic URSA Mini Pro 12K, 6K is a Super 16 sensor crop or “windowed mode”. The full 17: 9 DCI Super 35 sensor (27.03 mm x 14.25 mm) can be used for 12K, 8K and 4K recordings.
Since the processing is easier, you can use the full sensor to record 4K files or 12K files. If you have a shoot that needs to be online a few hours later, or where you are capturing hundreds or thousands of hours of footage, you can use the same camera that you use for 12K footage as it can handle this internal downsizing with no windows.
If you use the full sensor, you can use the lenses you already have for both normal footage and slow motion. With a Bayer camera, ramping up to slow motion often requires “windowing” the sensor to a lower resolution, and as you shut down the window, your field of view on the lenses will change.
The 12K camera allows you to keep the same lens that you used for normal shooting and simply set the camera to slow motion, which is a huge time and rental savings.
Many productions would rent a couple of extra-wide super 16mm primes for slow-motion shooting, and you can save yourself that cost now.
Some of you may now be asking, “But wait, RAW formats are not being debayered, how does that matter?”
Since Blackmagic not only makes the camera, but also makes the most widely used post software for color correction (Resolve) and the codec used for recording (Blackmagic RAW), they control the entire pipeline to keep it running smoothly.
12K Blackmagic RAW files viewed with an RGBW sensor are played back absolutely smoothly even on relatively less powerful devices. In tests, even the lightweight 13-inch MacBook Pro can handle the files, as the same simple processing as in the camera is also done in post-production with the simpler demosaicing that RGBW enables.
Here’s what you need to remember:
- The 12K resolution makes it perfect for 8K or below mastering
- You can shoot 12K, 6K, 4K or 2K with the same lenses without renting super wide angle super 16mm lenses for slow motion
- Simple processing allows working with less powerful computers in RAW