Depth Of Field For Film Explained

Aperture or depth of field can help focus your audience’s attention and give your films a cinematic look. So let’s get into what aperture is and how you can use it.

Similarly to shutter speed, your camera’s aperture controls how much light will be exposed on your camera’s sensor by creating a smaller or larger hole for the light to pass through.The difference is, shutter speed affects the amount of time the sensor is exposed to light, while aperture affects the amount of light the sensor is exposed too.

The aperture on your camera is represented in what are called f-stops, and the basic principle to know is that higher f-stop numbers equal less light, while lower f-stop numbers equal higher amounts of light. That’s because a higher f-stop number is a much smaller hole, while a lower f-stop number is a much bigger hole, as you can see here. An easy way to remember this is that when your lens is at the lowest f-stop number it can possibly be, it’s called being wide open because the adapter hole is at its widest.

And this is mainly important to know because it affects your depth of field. Depth of field is basically what’s in focus in your frame. So lower f-stops will result in a shallower depth of field, like you see here with the background nicely blurred out, while higher f-stops will result in more depth of field, like you see here where the subject and the background are both in focus.

First let’s go over shallow depth of field. Shallow depth of field is when most of the background is blurred out and there’s a very small amount in the frame that’s in focus. This also helps your film feel more cinematic. To achieve this, I recommend using an f-stop around 2 or 2.8. This will give you a nice shallow depth of field while still keeping the subject in focus.

This is great when shooting a close up of an actor or an insert of an important object because it focuses the audience’s attention on what you want them to be looking at, rather than being distracted by anything in the background. However, 2 is a pretty small amount of depth of field, so keep that in mind. Your camera operator might need to ride the focus ring on the camera to keep your actor or object in focus if there’s a lot of movement.

If you want to play it safe, then I recommend using the slightly higher f-stop of 3 or 4. This won’t give you as much of a background blur but it will be plenty depth of field to keep your actor or object in focus and allow for a slight out of focus background.

Also note that each lens you purchase will have a lens speed. This basically refers to how low of an f stop the lens can go to. So for example this lens has a speed of 2.8. (Hold up 70-200) That means when this lens is wide open it’s aperture is an f2.8. So keep that in mind when purchasing lenses if you want that shallow depth of field look.

Next let’s talk about a wide depth of field and when you’d use it. A wide depth of field is usually an f stop of 11 and up. Wide depth of field is generally used when you want to show scope of a character’s surroundings through a super wide shot or if you have multiple characters or objects in a scene you want to all be in focus. A wide depth of field ensures the audience can take in all the details at once and doesn’t miss any important action or element.

An easy way to keep track of when you’d use shallow depth of field verse when you’d use a wide depth of field is to just think of your shot choice.

The tighter your shot is, the shallower the depth of field you’ll most likely use to focus attention. While the wider your shot is, the wider you’ll want your depth of field to be to make sure no important details are blurred out.

Now that being said, you can still have story motivated reasons to choose differently for these examples. These aren’t really rules, but more guidelines that most filmmakers use. At the end of the day, the important thing is to choose the aperture that fits the story you’re trying to tell and affects the audience the way you want. So there you go! Now you're sure to be focusing the audience’s attention with aperture.

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