Gearing Up for 4K Production, Part 2: Cameras and Lenses

Lens Mount Types

One key differentiator for interchangeable-lens large-sensor camera is lens mount type. There are common mounts, like the PL-mount, which is the professional standard. Sony offers the E-mount, and Panasonic and Blackmagic support Micro Four Thirds. The mount you choose can make or break your entire workflow, or at least limit or enable it in terms of what’s powered, what’s stabilized, what’s active, and what’s not.

There are many factors to consider when pairing your lenses with your camera bodies. A lot of producers use Canon photo lenses on Sony cameras. Powered adapters were hard to come by in the past, but now they’re available from manufacturers such as Metabones (Figure 3, below). Before the availability of powered adapters, shooters who wanted to combine Canon lenses with Sony large-sensor cameras were unable to control the electronic iris on the Canon lens, and forced to shoot wide open the entire time.

Figure 3. The Metabones EF – E-Mount adapter

So, the question of whether the mount can power the lens is definitely an important consideration when choosing cameras and lenses. Sensor size is also a key consideration; it affects the low noise at high ISO, the ability for the camera just to soak in light. The larger the sensor is, the larger the photoreceptors. Larger photoreceptors can sometimes draw in four or five times more light, which is great when you need to get a good shot in a dark room.

One of the cameras that I use now is the Sony a7S (Figure 4, below), which is a full-frame 4K-ready camera. Its real claim to fame is that it can get clean shots in low light. At 100,000 ISO the a7S can produce a clean, usable image. It's cleaner than the image that Sony’s second-generation prosumer video cameras could produce at 0 dB. Even though ISO and dB are different scales, it's a massive difference. The a7S can see in the dark.

Figure 4. The Sony a7S

Sensor Size and Type Considerations

Another important consideration is video vs. photo sensor. A sensor designed for photo use, whether it’s 16, 18, 20, or 50 MP is not the best for video, because you can't process 60 frames or 30 frames per second of that resolution in cameras as they are today and use every single pixel. Whether you’re recording in HD or UltraHD or Cinema 4K, you don't need to start at 50 megapixels. You want to make sure that the sensor on your camera is designed for video use a high frame rate, and that it doesn’t throw away pixels at the edges, leading to pixel bending and funny things like that.

A good rule of thumb, in terms of how much extra resolution to look for, is two times the recording resolution on the sensor. So if you want to shoot in 4K, which is 8MP, then maybe 16MP is a good fit. Just be aware that there are photo sensors, and there are video sensors, and don't assume that one will replace the other.

When it comes to camcorders, for 4K camcorders, you'll see in the bottom left here there, a sensor size comparison. In Figure 5 (below), on the bottom right, the blue indigo box represents the 1/3” sensor that you’ll see on most camcorders. They’re tiny compared to full frame or the APS-C sensors, which are similar in size to Super 35.

Figure 5. 4K camcorders sensor-size comparison. Click the image to see it at full size.

The difference, though, is that when you’re working with a large-sensor camera, your options for finding a capable zoom lens are limited. With camcorders, you typically find zoom lenses of 10x, 20x, or 25x. This gives you a lot more versatility. It’s native. It’s portable. Everything is built into the camcorder. What I don't love about smaller camcorders is their lack of functionality. The two camcorders pictured in the bottom right in Figure 5 are tiny handheld camcorders that have only one ring. You can switch between zoom or focus, and sometimes iris, but professionals want three rings. That’s a big difference.

With 4K, do you really need a bigger lens? To some extent, yes. Not every approach will work, such as combining an HD lens with a tiny sensor. The two Sony cameras shown in Figure 5 are 1”-sensor cameras. I think will be the sweet spot moving forward. As you can see on the chart in the image, the 1” sensor is slightly smaller than the Micro Four Thirds, which is a very popular format found on cameras like the 4K-capable Panasonic GH4. It gives you a somewhat shallower depth of field. You get a larger sensor to get a better quality image, and you can still have zoom lenses on there. Sony doesn't currently offer any 1”-sensor cameras outside of the handheld form factor. I'd like to see them offer a bigger camera at that sensor size, and perhaps they will somewhere down the road.