Finding the right lens for your camera can vastly improve your images and overall production, but learning what you need to know about video and photo camera lenses can be expensive and time-consuming.
In this article, we explain photo and video camera lenses so that you can not only understand how your lens and camera work together but also which lens, or set of lenses, is the best option for you moving forward.
Video Camera Lens Basics
ESSENTIAL CAMERA LENS KNOWLEDGE
0.1 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…
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 allows a certain amount of light inside the lens.
- The lens elements bend light to specific points in the lens.
- The light is focused onto the image sensor or film plane.
1.1 VIDEO CAMERA LENS BASICS
What does mm mean on lens?
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:
This number is known as the focal length of the lens.
For this lens above the focal length is 17-50mm.
In this specific case, the lens ‘mm’ meaning or 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 you can see with your shots
- 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.
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.
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.
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 the light that passes through the lens to the image sensor or film.
This is measured in:
F-Stops (Estimated Measurement)
T-Stops (Exact Measurement).
You will normally find T-Stops used when describing the best camera lenses versus a standard digital photography lenses.
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.
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 numbers have shifted over the years.
When would I use a non-standard shutter speed?
How about the Omaha Beach scene in 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.
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.
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.
As you noticed from the video above, your subject matter can help determine which aspect ratio is best for your project.
Consider this when selecting a camera lens.
Video Camera Lens Explained
THINGS TO KNOW ABOUT CAMERA LENSES
2.1 VIDEO CAMERA LENS EXTRAS
What is lens breathing?
Lens breathing is the amount of shift in your angle of view when focusing. Most high-end lens manufacturers will eliminate breathing completely, but if you’re looking to buy or rent a kit for your low budget film you’ll want a kit that has little breathing.
In still photography this isn’t much of an issue because an image is a single frame. Can you imagine your frame composition changing while pulling focus in a scene? Less than ideal.
2.2 VIDEO CAMERA LENS EXTRAS
What is lens flaring?
Lens flaring is when light is scattered in a lens system, usually caused by bright lights that shine directly into the eye of the lens.
Lens flares are often considered to be unwanted artifacts in your image.
2.3 VIDEO CAMERA LENS EXTRAS
What is chromatic aberration?
Chromatic Aberration is your lens failing to focus all colors to the same convergence point. This normally presents itself as “fringes” of color along boundaries that separate the light and dark parts of your image.
This is one of those really advanced lens specs that professional cinematographers give attention.
2.4 VIDEO CAMERA LENS EXTRAS
What is bokeh?
Bokeh is a term used to describe when a lens renders out-of-focus points of light. It comes from the Japanese boke, and translates to “blur” or “haze”. There are at least three types of Bokeh you can achieve:
As you can see from the video above, different lens quality changes the type of bokeh you’ll be able to achieve. Even your custom bokeh will look a little different when using an anamorphic lens.
2.5 CAMERA LENSES EXPLAINED
What is focus throw?
Focus Throw is the physical rotation of the focus ring from the MFD (Minimum Focus Distance) to ‘infinity’. This is measured in degrees.
It’s how much room you actually have to pull focus.
Cinema lenses have a dramatically higher throw than still photo lenses.
The throw is very important in cinema and television because you need to make pinpoint adjustments when pulling focus from one subject to another. The more degrees available, the more accurate your focus pull.
Performing focus pulls with still photography lenses can also shake the lens, resulting in footage that may be deemed unusable during the edit.
There are focus pull accessories for still photography lenses, but the actual focus throw will likely remain the same.
Types of Camera Lenses
So, what does the camera lens do? Beyond focusing light to the focal plane, your camera lens creates the way your viewer watches your story. It changes the way you communicate with your audience.
All of the information you just read works for digital cameras and for film cameras, and that’s the beauty of lenses. Beyond some lens quality and lens technology advancements, lenses have stayed the same for centuries.
Now that you have a better grasp on lenses, check out our post on the Understanding Camera Lenses: Types of Camera Lenses.
We explain how each lens is categorized, the technology and science behind it, and how they’re used in filmmaking and photography.