3 Basic Camera Settings Every Cinematographer Should Know
EXPOSURE TRIANGLE
The first step to being a good cinematographer is to understand how images are created.
You need two things: a photosensitive surface, like a camera sensor or a piece of film, and light. How much light hits the sensor and the sensitivity of that sensor determines how an image looks. This is called exposure.
If too much light is used the image will be too bright, and if too little light is used then you won’t be able to see anything at all.
Therefore, cinematography is all about controlling light.
In this video I’ll take you through three of the most important camera settings that will allow you to control the amount of light that is let into the camera: ISO, shutter and aperture. This is sometimes called the exposure triangle.
If you’ve ever used a consumer camera you may know that there is an auto mode that will adjust all of these settings for you. So, you may be thinking, why not just use that?
I’d say there are two main reasons why changing the settings yourself, called manual exposure, is the preferred method for anyone who wants to take image making seriously.
Number one. When you put the camera in auto mode you are basically giving it permission to constantly change and adjust various settings at will to get you to an evenly exposed image.
The problem with this is that we will often be able to see the video footage changing from dark to light as it adjusts settings until it finds a level it is happy with. This can be very distracting and breaks the illusion of filmmaking, taking the audience out of the immersion in the story as they say to themselves, “OK, this was obviously shot on a camera.”
Number two. Cinematographers want to be able to precisely control how they want the image to look and not leave that decision up to the whims of a camera. They may want a comedy to look light and bright, a drama to look dark and moody, have a deep depth of field where everything in the image is sharp, or make the background soft, blurry and dreamy.
ISO
ISO, ASA, or EI are all terms that refer to the sensitivity of a camera’s sensor or a film to light. The higher the ISO number is the more light will be taken in by the sensor and therefore the brighter the image will be. And inversely the lower the ISO, the less light it absorbs and the darker the image is.
Therefore, it’s common to set the camera to a lower ISO when shooting outdoors in bright sunlight, and a higher ISO when shooting in darker conditions at night.
However, higher ISOs come with a tradeoff. The more that you increase this setting the more digital noise, those little dancing grainy specs, you will see.
Most digital cinema camera manufacturers will recommend shooting at a base ISO or a native ISO. Although this differs for each manufacturer, base ISOs usually offer the best trade off between a high quality, low grain image and a good dynamic range.
For example, most Arri cameras have a native ISO of 800. Some cameras, such as the Sony Venice 2 also have what are called dual base ISOs: such as a lower native ISO of 800 and a more sensitive native ISO of 3,200.
So, when setting up your camera to shoot each shot you need to pick an ISO based on two factors. Firstly, consider how much noise or grain you want the image to have, and secondly decide how sensitive you need your camera to be to shoot in the lighting conditions.
And, if you’re still in doubt, it’s probably best to set and leave the camera at whatever base ISO the manufacturer recommends, keeping the noise as clean as possible, and rather adjust other settings.
SHUTTER
Instead of changing the sensitivity of the sensor, another way of altering exposure is by controlling how much light hits the sensor. This can be done with the shutter: a section that can open up to expose the sensor to light, or close and prevent light from entering the camera.
This setting determines the duration for which a camera’s sensor is exposed to light.
In photography this is measured in shutter speed: the time a single frame is exposed to light, by quickly opening then closing a rectangular blind shutter. Usually this is measured in fractions of a second, like 1/100.
Cinema cameras need to shoot multiple frames within one second, for example 24 frames. Therefore, they need a differently designed shutter: one shaped like a circle that can spin.
More or less light can be let through depending on what angle is cut out of the circle. For example, 180 degrees may be cut out, so that each frame is exposed to light for half the time by the open shutter and not exposed to light when the closed half passes the gate.
Or, a 45 degree angle can be used, where only a narrow sliver of the shutter is open. This means that each frame is exposed to light for 1/8th of the time. Less light means the footage will be darker, and it also makes motion feel more choppy.
A 180 degree shutter angle is most commonly used because it gives the footage a normal feeling of motion that is not too jerky or too fluid.
Modern digital cinema cameras don’t have a physical shutter that opens and closes, but it uses the same principle by telling the camera’s sensor when to collect light and when not to collect light.
If using a camera with a shutter speed setting, a good rule of thumb is to set it to be double the frame rate - to get a normal feeling of motion. So if shooting at 25 frames per second, we will set the shutter speed to 1/50. Then if the camera increases its frame rate to 50 frames per second, we will double that and set our shutter speed to 1/100.
APERTURE
Moving even further away from the sensor, we get to our final important camera setting that controls exposure: aperture.
This is the size of the opening at the front of the lens through which light passes to get to the sensor. The size of the hole is controlled by iris blades narrowing or opening and is measured either in f-stops for photography lenses or t-stops for cinema lenses.
The wider this opening is, the more light is let through and the lower the stop value is. On the other hand, the narrower the iris is, the less light it lets through and the higher the stop number is.
Each stop represents a doubling, or halving of the amount of light that hits the sensor. So, to make the image brighter we need to decrease the stop number by doubling the light let through - for example from 4 to 2.8. Or to make the footage darker and cut down on half the light let through we can increase the stop from 2.8 to 4.
The aperture setting is a very effective way of changing how bright or dark an image is. However, aperture also has another, secondary effect on the image.
The wider the iris is, and the lower the stop number, the shallower the depth of field will become. In other words a low stop number means that more of the background will be out of focus.
Since cinematographers often like to shoot with a shallow depth of field that makes the background look soft and focuses on a single subject, the camera is often set to a low stop number, such as 2 or 2.8.
THE FINAL SETTING
But, this runs us into a snag. We’ve set the ISO to the base of 800, we’ve set the shutter angle to get normal motion at 180 degrees or 1/50th of a second, and we’ve set our aperture at 2 to get a shallow depth of field. However, the image is still too bright.
How do we make it darker and get it to the level of exposure that we want without changing our other settings? We can use what are called ND, or neutral density, filters.
These are pieces of tinted glass which are either placed in front of the lens, or inside the camera behind the lens, that decrease how much light is let into the camera without changing the colour of the image.
Adding a stronger tinted ND filter will take away more light, while a weaker strength filter will take away less light. Each stop of light taken away is represented by a value of 0.3.
So, most cinematographers will set the camera with a consistent ISO (to keep the same grain), shutter (to keep the same feeling of motion) and aperture (to keep a shallow depth of field) for most shots, then use ND filters to cut down on how much light enters the camera.