VIDEO CAMERA LENS BASICS Photo and video camera lens basics If you know about aperture and focal length, feel free to use our Table of Contents to jump down right to the ‘good stuff.’ If you know nothing about camera lenses… Keep reading. Camera lenses and optics in general have been improved upon long before the invention of the camera, because lenses were useful centuries before the Lumiere Brothers were even born.

CAMERA LENS DEFINITION What is a camera lens? A camera lens is an optical body that features a single lens or an assembly of lenses that mounts to a camera body. Some lenses and interchangeable, while others are built into the construction of the camera body. Modern lenses attempt to set the angle of incidence and angle of refraction to equal values to decrease the amount of aberration, and feature a focus element that allows the operator to dictate which portions of the image are acceptably sharp, and which portions are blurred.

How do camera lenses work? Aperture dictates the amount of light that passes through the lens.

The lens focuses the light onto the image sensor (digital) or film plane (analog).

1.1 VIDEO CAMERA LENS BASICS Focal length basics What does "mm" mean on a lens? Well, on the side and front of your camera lens you will find a small "mm" with a number, or set of numbers next to it. It will look something like this:

Camera lens mm - Focal Length

This number is known as the focal length of the lens. For this lens above the focal length is 17-50mm, meaning the focal length can be changed from any number in the 17mm to 50mm range. This change is referred to as a variable focal length, or... zoom. You can zoom in from 17mm. You can zoom out from 50mm. This is the range of the variable focal length of this lens. It cannot go under 17mm, and it cannot go above 50mm. When it comes to camera lenses, your focal length will not only allow you to capture footage with different visual properties, but those properties will change the emotional effect the footage or image will have on the viewer. There are both practical and creative reasons for choosing a specific photo or video camera lens, so understanding focal length might be the most important visual tool for a filmmaker or photographer to understand.

FOCAL LENGTH DEFINITION What is focal length? Focal length is the distance between the optical center of the lens, and the camera sensor or film plane when focused at infinity. The optical center is where light rays converge inside the body of your lens. The focal length defines the magnification and field of view for a given lens. This value is most commonly measured in millimeters. Prime lenses have set focal lengths whereas zoom lenses have variable focal lengths, and any change in magnification alters the visual properties.

Why is focal length important? Focal length dictates what part of the image is in focus, isolating elements in either the foreground, middle ground or background

Focal length generates visual context for your shots

Focal length alters the visual properties of your shots

A basic way of explaining focal length is the magnification of your lens. A longer lens will give you a narrow image that is closer to the subject, whereas a wider lens will capture more of the area from further back.

Focal length

Some high-profile performers even have a “lens clause” built into their contracts that limit the focal length of any lens used to capture their image. These performers understand the power of focal length. They have a desire to retain some control over their professional images, and while this isn’t an option for a traditional actor, certain musical artists and social media stars want to keep their image consistent. Some people may refer to the focal length at the lens size.

Shot list with lens size | StudioBinder

Any lens with a focal length 35mm to 55mm is categorized as “standard” focal length. This is because the human eye has a similar field of view. There is vast discussion on this topic, and some even say a more accurate human focal length to be closer to 22mm. This is a relatively low focal length for narrative filmmaking, but that doesn't mean you won’t use it, and some directors will use it often. Focal length matter both for photo lenses and video lenses because a photograph or a video recording that used a 50mm lens will have a drastically different look and feel to one that was captured with a 20mm. Here is a scene from Blade Runner 2049 where the camera is simulating a pair of binoculars, and to recreate the visuals you might get from optics like this example below, the filmmakers would use a long angle lens, like an 85mm.

Long focal length used to simulate binoculars

This is one example of using a specific focal length of lenses for practical application in your story, but focal length can also be used for emotional reasons. 1.2 VIDEO CAMERA LENS BASICS What is camera lens aperture? Aperture describes the light intensity of a specific image or set of images. Lens aperture controls light that passes through the lens to the image sensor or film. This is measured in: F-Stops (Estimated Measurement) or... T-Stops (Exact Measurement). You will normally find T-Stops used when describing the best camera lenses versus a standard digital photography lenses.

Understanding Camera Lenses Explained

T-Stop and F-Stop are not the same, though they are commonly mixed up or used in place of one another. Professional filmmakers deal with T-Stops… While many digital photography and indie filmmakers use the term F-Stop, it really depends on the lens you’re working with. Just know that they both refer to aperture stops. The lower the stop number... The higher the aperture (wider the opening). That means that a T2 is higher than a T8. That’s because the aperture is wider, and therefore lets in more light. Higher light intensity = Higher stop number Camera lenses with higher stop ratings and wider openings allow more light, which means you can film in darker locations. Aperture range of a lens is expressed by the lens ratio (focal length divided by max aperture).

1.3 VIDEO CAMERA LENS BASICS What is shutter speed? Shutter speed is the amount of time the shutter is open. This is typically measured in fractions of a second, especially with video recording. With still photography, shutter speed is much less rigid than with cinema & television because still photography is viewed as a single frame. But for video... 98% of the time you’ll want your shutter speed to double your frame rate. 98% of the time you’ll want your shutter speed to double your frame rate.

Shutter speeds

Cinema Frame Rate The standard frame rate is 24fps (23.976fps), which means your shutter speed should be set at 1/50. This means the sensor is exposed for 1/50th of a second. Television Frame Rate The standard frame rate is 30fps (29.97fps), which means your shutter speed should be set at 1/60. This means the sensor is exposed for 1/60th of a second. You may notice that the math here is off a bit, and there are some very complicated and logical reasons why these numbers have evolved over the years. When would I use a non-standard shutter speed? How about the Omaha Beach scene in Saving Private Ryan?

Shutter Speed | Saving Private Ryan

In this scene, the crew actually replaced the shutter blades to shorten the amount of time the film was exposed. This created a jagged look that really works well for action. Most likely you’re not going to replace the shutter on your camera. You can achieve a similar look by increasing shutter speed to 4x or 8x the frame rate. Example: If you are shooting a film at 24fps, you might set your frame rate at 1/100 or 1/200 to achieve a choppy, staccato look. Math is your friend in film & television. 1.4 VIDEO CAMERA LENS BASICS What is depth of field? Depth of field refers to how much of your image is in focus, and more specifically the area of acceptable focus. A shallow depth of field will give you a blurred background, while a large depth of field will keep everything in focus so that we can see everything around us.

Depth of field explained

With a shallow depth of field, your viewer (often) has less imagery to digest, and you can place more emphasis on a specific part of your frame. In this example below, you can see acceptably sharp imagery all around the frame, and even far off into the distance. This shot has a large, long, or deep depth of field.

Camera lens specs from Blade Runner

Other times you want your entire scene in focus to allow your viewer to “drink it all in”. It’s a toolbox. Different tools for different jobs. You wouldn’t use a hacksaw to hammer in a screw, would you? Depth of field is such an important topic that we created a dedicated post, so check out The Essential Guide to Depth of Field [with Examples]. We break down how you can control your depth of field, and provide professional examples from photography and film. 1.5 VIDEO CAMERA LENS BASICS What is an aspect ratio? The aspect ratio of a lens is determined by the sensor size (or film size) of the camera with which it is intended to mount. If a lens is built for an APS-C size sensor, it will not line up correctly with a full-frame camera. You may have the correct mount, so the lens will physically attach to the camera, but it won’t have the correct opening size, and thus creates a vignette where the light is absent. Our video on aspect ratios shows you how different ratios are used for presenting final cuts of projects, but your camera lens aspect ratio cannot be changed, as it is baked in the construction of the lens.

Aspect Ratios | StudioBinder