Best ISO for video – what is ISO and how to use it?

If you want to know what ISO is, how to choose the best ISO for video  and how to set the most optimal ISO value to get the best image quality, you are in the right place.

ISO – definition (photography / videography)

Let’s start with what is ISO. Before we jump into this, we need to understand what exposure is in general. Simply put, the exposure determines how much light enters the photosensitive material in our camera. It affects how bright the image we are filming is. Our goal is to set the correct exposure value, so we can get the footage in which we do not deal with overexposure or underexposure. If the sensor does not receive enough light, we say that the image is underexposed. On the other hand, if too much light falls on the sensor, we are dealing with the overexposed image.

We already know what exposure is. So how can we manage it? The exposure has three main parameters that can be set on our camera. This is the ISO value, shutter speed and aperture.
Using the ISO value we can control how sensitive the sensor is to the light. Basically, low ISO means a darker image, higher ISO means a brighter image.

ISO is helpful when we don’t have enough outside light. For example, if we go outside on a sunny day, then by setting the minimum ISO value to 100, we will be able to record footage that is properly exposed. However, if we enter a dark room where the light is really low, then we need to increase the ISO to set the right exposure.

What happens when you change ISO on film camera?

It seems so simple. If we’re dealing with shooting in dark conditions, we just need to increase our ISO to set the right exposure, right? Well, not really.

We need to know that increasing ISO has some consequences, such as the level of noise that appears in our image. The higher the ISO value, the more noise in the image, which means that the quality of this image is just really low. You’ll notice that especially when shooting in dark rooms or outdoors at dusk.

What is the best ISO for video?

So how do you determine which ISO value is the best? Simply put, the lowest ISO possible under given conditions will give us the best image quality. To determine this, we need to control the exposure value that appears on the screen of our camera. Generally speaking, we want the value to always display zero. Ok, but what if, for example, we have a very sunny day, we are outside and we set ISO at 100 and we can not go lower, and yet our image is overexposed and the exposure value indicates +2, +3? In that case we have to use either the aperture value, close it more to allow less light on the sensor or use an ND filter. Eventually, we can also use faster shutter speed, but in the case of filming, we should avoid it, because we always want to keep this parameter at 2x frame rate, for example, if we shoot in 24 frames per second, we should keep the shutter speed at 1/50 of a second but take it easy, we’ll talk about this in another movie.

What is the highest ISO I can use in your camera?

We already know that we should always keep the ISO value as low as possible. But there are situations when we are forced to raise ISO, for example, when we shoot in a dark room and we do not have external light. What maximum value can we reach then? It depends on the camera we use. For example, I use Sony mirrorless cameras for my work and setting ISO at 3200 or even 4000 gives me the image with a decent level of noise. However, I still remember the times when I used the Nikon P900, in which ISO 3000 already made the image quality just terrible.

What ISO should I use at night?

Let’s go a step further. We are in a dark room, we have no external light, we set ISO to 4000 but still, the image is very dark and you can hardly see any details. Well, the only way out in this situation is to use the lens that allows a larger aperture. Lenses with a maximum aperture of 1.8, 1.4 or even 1.2 work really well in low light conditions and give us a nice image quality.

Auto ISO or Manual?

If you go to the ISO settings, you will notice that each camera has the option of automatically setting the ISO. Should you use auto ISO? I’d rather not do that. The reason is very simple. When you move around one room, the lighting conditions in a particular part of the room will be different. This will mean that the ISO value will change as you move and this will give you an unpleasant, unprofessional effect.

How often you use the maximum ISO is also determined by the size of the sensor in your camera. If you use Sony A6300 or A6500 the sensor is smaller than in full-frame cameras such as Sony A7. A larger sensor means a larger amount of light entering the photosensitive material, so full-frame cameras perform better in low light conditions than those with an APS-C sensor.

Check your camera’s Native ISO

It’s good to check what is your camera’s native ISO. In a lot of cases it’s ISO 200 which will give you the best image quality with the least amount of noise. In this case, if you choose ISO 100 you’ll get more noise in your footage than at ISO 200.

That’s all you need to know about ISO. Now it’s time to move on to the next parameters that affect exposure, which is shutter speed and aperture. If you find this filmmaking tutorial useful and you would like to make a living with filmmaking in the future, like me, please join my newsletter so that you don’t miss notifications about new articles and tips that I will post on this blog.