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

When I talk about cameras with other video producers, one of the questions that I always find interesting is, "Do you need a 4K lens to shoot in 4K with interchangeable-lens cameras?" A lot of camera companies now are coming out with “Cinema 4K-class” lenses. I question that designation--at least the purported uniqueness of it. 在分辨率方面, 4K意味着4,000像素宽, which translates to 8-9 megapixels (MP) in photographic terms. 这是一个不同的长宽比, 当然, but 8-9 MP is actually pretty modest for a still camera when you consider that today’s entry-level photo cameras offer 16-18 MP.

Do you really need a "4K" lens for something that's shooting at a smaller size? 对我来说，答案是否定的. Of course, it's great marketing for them to promote their high-end lenses as “Cinema 4K.“这并不意味着这些不是很好的镜头, 当然; their ability to capture 8 MP images just isn’t their key point of differentiation.

If you're shooting 4K for the big screen and your budget is unlimited, by all means get yourself Cine Zoom lenses that cost $40,000-80,000个(下面的图1). But you don’t need a lens that expensive to shoot 4K for the web. 在现实中, 你可以用专业的单反镜头, and even some of the consumer ones do a great job for 4K as well.

图1. 佳能4K电影镜头售价7.8万美元

作物传感器格式

If you shoot with DSLRs, APS-C is the crop sensor format that you work with on your cameras. Some cameras also shoot full frame, which is comparable in size to old 35mm film. 在视频方面, while some full-frame 4K video cameras have either recently come to market or are coming soon, Super 35mm seems to be the sensor size that's the most common right now. 它在大小上与APS-C非常相似.

Because APS-C cameras do not use the full frame in the sensor, 任何镜头的最佳位置都在中间. 当你走到边缘, 锐度减弱, 造成晕光和暗纹等问题. 最佳位置在中间. Pairing a Super 35 sensor with almost any photo lens will achieve excellent results. You don't need it to be the sharpest lens in the world, 因为你不需要5000万像素, 即使是4K. In general, prime lenses are sharper than zoom lenses.

4K大传感器摄像机

I'm a big fan of large-sensor cameras because the sensor is so massive that you don’t have to do any interpolation of the image that comes from the lens. 小型摄像机有微小的6-7毫米(对角线)传感器. 相比之下，超级35mm相机有28个传感器.5mm对角线(下面的图2).

图2. Sony’s PXW-FS7 XDCAM camcorder, a recently introduced Super35mm 4K model

Sensors of this size make it possible to achieve shallow depth of field, 当你在网络直播的时候, 你肯定想要那种造型. Your bit rates are so aggressive when you're webcasting that you don't want noise, 你不想要太多的细节. Your subject needs to be sharp and in focus at all times. You want to allocate all your available bits to maintaining focus on your subject, and one way to maximize the bits available to your subject is to sacrifice focus on the background. 大传感器相机给了你这种能力.