How Auto ISO Can be a Valuable Tool for Filmmakers and Videographers

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ISO can be a sticky subject when it comes to video. It is used in photography when you have a great amount of control over your aperture, shutter, and exposure, and when you understand the lighting of your environment. But when used in video, if used too often, it can be more of an enemy than a friend to your footage. The most controversial setting is auto ISO, causing you to lose control over your ISO setting—and it can have mixed results. However, there are times when auto ISO can be your friend.

What ISO Is and What It Is Not

Technically, ISO stands for "International Organization for Standardization," the body that publishes global measurement standards. It originated to describe photo film stock ratings, when you'd have to choose your film speed based on the amount of light you'd be using and how you'd have liked it exposed. If you were shooting outdoors during the day, you'd choose ISO 100 or 200 film stock. If indoors, you might choose ISO 400 or 800 depending on the light, what lens you were using, and so on.

Similar to pre-chosen film stock, digital ISO doesn't technically involve exposure, since its functions take place post-shutter, post sensor, and it does not directly relate to how much light is let into the camera. It is basically a digital offset, or command, for what the sensor "prints" to the recorded image. In the old days when video was analog and sensors were small, the gain function served the purpose of amplifying the video signal electronically, rather than using exposure tools. With the arrival of DSLR technology, and now that digital cinema cameras are in the hands of industry professionals, the old film stock term stuck. So, if you have a previous understanding of gain, it should translate easily to understanding digital ISO.

Video grain/noise
Video grain/noise

The main downside of high ISO settings in low-light conditions, similar to the effect of high gain on older cameras, is pixelation or noise the higher you go. If you've ever seen an image with a lot of noise, you know it just won't work. Pixels of different colors show up in the dark areas, lighter areas may appear overexposed or washed out, making your images look amateurish and cheap.—which is why its use in video is usually frowned upon.

But Not Always

New cameras with large sensors are continuously getting better at offsetting the grain using digital correction. I remember when a friend got a new DSLR with a powerful sensor and he set it to an extremely high ISO setting like 16,400 or higher in a dark room, and it didn't look too bad. But the grain was still there in the fine detail, and of course it worsened as the setting was pushed higher.

When shooting video, shutter speed and aperture are your friends. You want that beautiful, soft, buttery bokeh? Choose the right f-stop, shutter speed, use a filter, set your focus in the foreground, hit record. But if your subject is roaming, the light conditions keep changing, and you don't have all that much time to change your camera settings in a documentary or run-and-gun situation, it isn't a bad choice to use your auto functions.

For example, I once had a job shooting a video on a science ship and had a limited amount of time to record the guides talking. We had to continuously climb down into the hold, walk through the living quarters, and climb back up to the outside deck. I also was carrying two cameras (one cinema rig and one gimbal action camera) to get both wide and close shots when recording the tour. My hands were full, and I had no chance to adjust my focus or exposure settings while on the move. Along with the changing focus situation, my light kept changing. To make things worse, it was raining on and off, and the light outside was changing in addition to the inside. Some rooms had windows, but below deck was only lamplight. Impossible videography situation.

Low Light, High ISO
Low Light, High ISO

So, I set my cinema camera to autofocus and auto ISO. Though it was a bit difficult to prevent the ISO from going way too high in some dark places, the ship was fairly well-lit ("science-ing" needs light) so the recordings had minimal grain. But if you have issues with keeping a decent image, or your auto ISO seems hard to control, some cameras may have an exposure compensation feature to make sure to push your exposure to meet ISO limitations, so it doesn't shoot up so high.

Deciding Ahead of Time

There are also some pro cameras by Panasonic that feature Dual Native ISO, a fairly recent technology that offers two optimal ISO presets, low and high, which can be set with a switch similar to using gain on an old camera. Since those settings actively adjust to what the sensor is reading, grain is minimized, and rich color depth is maintained. This setting lets you decide ahead of time which to use when in a very bright or very dark situation, so your aperture and shutter settings can be used as normal to compensate for the changes in light.

Though auto ISO isn't ideal, it tends to be a better way to brighten your images, rather than waiting to fix them in post—the adage holds up in most situations—especially if you're using a DSLR or professional camera with a high-quality sensor. Another option you might have is shooting in RAW format, if your camera supports it and you have the recording space, so you can control the ISO more finely. If you were in a low-light situation, and you weren't sure how much light you needed and would rather err on the side of darkness rather than grain, editing RAW images in post essentially does the job of the ISO function in the camera. Since the sensor is altering your image with the ISO setting, the file is merely RAW sensor data that is easily manipulated in post.

For more information about exposure and ISO in photography, read our four-part Understanding Exposure series, in Explora, and watch the basics of ISO Explained in a handy, concise video. Feel free to share your experiences with auto ISO below and be sure to check out all the available video cameras and accessories on the B&H website or try them out in person at the B&H SuperStore when you’re in New York City.

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