The 14.25° derived in Example 1 (see white box below) can be used to determine the lens that is needed, but the sensor size must also be chosen. As the sensor size is increased or decreased it will change how much of the lens’s image is utilized; this will alter the AFOV of the system and thus the overall FOV. The larger the sensor, the larger the obtainable AFOV for the same focal length. For example, a 25mm lens could be used with a ½” (6.4mm horizontal) sensor or a 35mm lens could be used with a 2/3” (8.8mm horizontal) sensor as they would both approximately produce a 14.5° AFOV on their respective sensors. Alternatively, if the sensor has already been chosen, the focal length can be determined directly from the FOV and WD by substituting Equation 1 in Equation 2, as shown in Equation 3.

Ring lights are exactly what they sound like: strips of LEDs built into a halo-like apparatus. By placing your camera, webcam or smartphone in the center of the ring, you minimize shadows and get flattering light that seems to come from everywhere, without creating shadows, harsh lines or distracting reflections. They’re perfect tools for making you look good on camera.

Ring lightsizes in inches

The EMart’s tripod can expand up to 50 inches in height but can collapse down to 19 inches, a perfect height to use on your desktop with your computer or tuck it behind your laptop. This flexibility gave the EMart major bonus points, as it was the only ring light we tested that peeked above laptop height even at its lowest setting. That means you can still use it straight on, as opposed to the others that you have to use off to the side a bit, which can lead to unwanted shadows.

By entering your email address, you agree to our Terms of Use and acknowledge the Privacy Policy. CNN and its affiliates may use your email address to provide updates, ads, and offers.

Once the required AFOV has been determined, the focal length can be approximated using Equation 1 and the proper lens can be chosen from a lens specification table or datasheet by finding the closest available focal length with the necessary AFOV for the sensor being used.

Note: As the magnification increases, the size of the FOV will decrease; a magnification that is lower than what is calculated is usually desirable so that the full FOV can be visualized. In the case of Example 2, a 0.25X lens is the closest common option, which yields a 25.6mm FOV on the same sensor.

This light was smaller than the other portable ring lights we tested but lacked in performance. The photos we took with this light seemed to have a white film over them that made them look unnatural or poorly edited. It’s more expensive than the Whellen Selfie Ring Light but didn’t provide nearly as good results.

The focal length of a lens is a fundamental parameter that describes how strongly it focuses or diverges light. A large focal length indicates that light is bent gradually while a short focal length indicates that the light is bent at sharp angles. In general, lenses with positive focal lengths converge light while lenses with negative focal lengths cause light to diverge, although there are some exceptions based on the distance from the lens to the object being imaged.

24 inchRing Light

By clicking 'Sign up', you agree to our Terms of Use and acknowledge the Privacy Policy. CNN and its affiliates may use your email address to provide updates, ads, and offers.

Another way to change the FOV of a system is to use either a varifocal lens or a zoom lens; these types of lenses allow for adjustment of their focal lengths and thus have variable AFOV. Varifocal and zoom lenses often have size and cost drawbacks compared to fixed focal length lenses, and often cannot offer the same level of performance as fixed focal length lenses.

Tiny but mighty, the Godox LEDM32 Smartphone Mini Light has a small clip on the back that fits easily on a phone and provided an extremely bright light. The light was almost blindingly bright, in fact, but the brightness could be adjusted using the plus and minus buttons on the top of the light. It charged really quickly, with the battery lasting almost two hours. The light looked great in photos and worked really well for video calls, but overall was overly bright and distracting during use.

The Whellen’s clip has rubber padding on the reverse side to prevent it from scratching your screen. And even with a case, we had no trouble fitting the clip on our phone (we were using the Incipio Organicore case, which adds 3.7 millimeters to the phone’s thickness).

Whatis the biggestsizeofRing Light

Example 2: For an application using a ½” sensor, which has a horizontal sensor size of 6.4mm, a horizontal FOV of 25mm is desired.

Long used by professional portrait and macro photographers as well as makeup artists, and perfect for selfies, streaming, vlogging and most photo and video tasks, they have become favorites of social media influencers and content creators of all kinds. But you don’t have to be a top Twitch streamer or overnight TikTok sensation to appreciate being cast in a better light on Zoom calls — they’re also the perfect addition to work-from-home office setups.

The Whellen Selfie Ring Light is extremely lightweight and small, so it easily fits in pockets, purses, backpacks — you name it. We stuffed it in a purse while grocery shopping, and even with keys, a phone, a wallet and some spare change around it, the light didn’t so much as get scratched.

The light has only one button, which toggles through the light settings. If you hold down the button while on any of the light modes, the light will dim so you can easily adjust brightness levels. Most other lights we tested required clicking through for different brightness levels, so the slow dim was a nice touch for the Whellen Selfie Ring Light. Once the light is at its dimmest, you can click and hold the top button again for it to come back to brighter levels until you reach the brightest setting.

Though this Kodak ring light provided flattering light with all three of its brightness levels, we noticed the brightness of the light starting to fade after the ring light was left on for longer than 30 minutes. It did, however, fit really well on our phone with or without a case, though it doesn’t fit well on thicker cases.

Ring Lightsizes and price

Note: Fixed focal length lenses should not be confused with fixed focus lenses. Fixed focal length lenses can be focused for different distances; fixed focus lenses are intended for use at a single, specific WD. Examples of fixed focus lenses are many telecentric lenses and microscope objectives.

Do I needaring light

Content is created by CNN Underscored’s team of editors who work independently from the CNN newsroom. When you buy through links on our site, we may earn a commission. Learn more

From the outset, the EMart ring light is extremely easy to use. The light, which is wide enough to use with most cameras itself simply screws onto the included tripod, which has three collapsible sections. The base upon which the light sits can turn 360 degrees around and you can pivot the light 180 degrees up or down, which ensures you get the perfect angle to decrease shadows when taking a photo or lighting yourself during virtual meetings. A Bluetooth remote is included to control the light’s setting if you place it at a distance.

As previously stated, some amount of flexibility to the system’s WD should be factored in, as the above examples are only first-order approximations and they also do not take distortion into account.

The EMart 10-Inch Selfie Ring Light ticks all the boxes for what you’d want in a ring light: It’s got tons of adjustability in terms of setup and lighting options, a lightweight design and can be used in multiple ways with a variety of cameras, making it a great option whether you’re setting it atop your desk for video calls or need some overhead lighting so no weird shadows creep into your photos. It brings it all together at an affordable price point, making it a clear winner among the ring lights we tested.

This option from Movo was different from all of the other lights we tested; the stand mount looks like a large chip clip, which lets you mount it to anything you can grab (the edge of a shelf or monitor, for instance), and holds three flexible, bendable arms, one of which holds the light, another a phone holder and the third a mounting point for an audio recorder, camera or other object. The lighting provided by this ring light was really crisp, but overall it isn’t as functional as the other portable lights we tested since it doesn’t simply sit atop a desk. But if you have a desk where you can clip it into place, this is definitely a great option.

22 inchRing Light

This is a good desktop option if you’re looking for a ring light to use while applying makeup, while filming videos or during virtual meetings. The tripod included is very short, so it sits at a good height on a desk but doesn’t adjust tall enough for use with a laptop’s built-in camera. It comes with a phone holder alongside a mirror for applying makeup, which was an added bonus. This light also gives you the option to mix warm and cool light at different levels with an indicator on the back. It lost points, however, because the tripod included is short and minimally adjustable. Plus, the light is much larger than the base, making it awkward and somewhat difficult to put together.

The 3.5-inch light clips right onto your phone or laptop. If you’re using it for the front-facing camera, the bottom half of the light will cover part of your screen, while the top half sits above your phone. That may sound annoying, but in use, it doesn’t block any important part of the screen — it never covered the other person while on a video call, and it essentially covers the same amount of space at the top of the phone as a drop-down notification, so you still see almost the entire field of view.

While most sensors are 4:3, 5:4 and 1:1 are also quite common. This distinction in aspect ratio also leads to varying dimensions of sensors of the same sensor format. All of the equations used in this section can also be used for vertical FOV as long as the sensor’s vertical dimension is substituted in for the horizontal dimension specified in the equations.

Field of view describes the viewable area that can be imaged by a lens system. This is the portion of the object that fills the camera’s sensor. This can be described by the physical area which can be imaged, such as a horizontal or vertical field of view in mm, or an angular field of view specified in degrees. The relationships between focal length and field of view are shown below.

Ring lightsizes in cm

To compile our testing pool, we read reviews, searched Amazon for the top-rated ring lights and looked at companies known for their lighting equipment. We then established parameters to test, looking in particular at brightness, color options and results in photos and videos.

Battery life is the only aspect that left us wanting. It took about an hour for the USB-powered light to fully charge, and lasted about an hour and a half. While on par with the entire field (almost all averaged the same life span), the included USB charging cable is only 10 inches long. So while other lights can remain plugged in while in use, you’ll have to supply your own cable to do this with the Whellen.

When using fixed focal length lenses, there are three ways to change the FOV of the system (camera and lens). The first and often easiest option is to change the WD from the lens to the object; moving the lens farther away from the object plane increases the FOV. The second option is to swap out the lens with one of a different focal length. The third option is to change the size of the sensor; a larger sensor will yield a larger FOV for the same WD, as defined in Equation 1.

\begin{align}\text{AFOV} & = 2 \times \tan^{-1} \left( {\frac{50 \text{mm}}{2 \times 200 \text{mm}}} \right)  \\ \text{AFOV} & = 14.25° \end{align}

Whatis the bestsize ring lightfor videos

In many applications, the required distance from an object and the desired FOV (typically the size of the object with additional buffer space) are known quantities. This information can be used to directly determine the required AFOV via Equation 2. Equation 2 is the equivalent of finding the vertex angle of a triangle with its height equal to the WD and its base equal to the horizontal FOV, or HFOV, as shown in Figure 2. Note: In practice, the vertex of this triangle is rarely located at the mechanical front of the lens, from which WD is measured, and is only to be used as an approximation unless the entrance pupil location is known.

Generally, lenses that have fixed magnifications have fixed or limited WD ranges. While using a telecentric or other fixed magnification lens can be more constraining, as they do not allow for different FOVs by varying the WD, the calculations for them are very direct, as shown in Equation 4.

Like our overall winner, though much more compact, the Whellen offers three different lighting options: warm, cool or a combination of the two — more than some of the larger and more expensive lights we tested. The cool setting is bright white, and the warm setting carries an orange tint. Even in the darkest of rooms or during nighttime use, both the warm light option and cool light options worked well, though we found the mix of both looked most natural and flattering.

Ultimately, the EMart 10-Inch Selfie Ring Light, thanks to its adjustability and various lighting options, was the best of the bunch we tested. Whether you’re using this light for a professional appearance in virtual meetings or for fun and creative content making, this is a great option. Plus, for a combo of light and tripod, the $35.40 price is relatively low while delivering high-quality results.

But what, er, shone brightest during our tests was the flattering light cast by the EMart, which came across as natural sunlight in both portraits and selfies. That’s made possible by the light’s three light modes (there’s warm, cool and a nice mix of the two) along with 11 brightness levels for each mode (the most settings of any of the lights we tested). In photos taken during both day and night, the lighting gave us high-quality images, highlighting everything it was supposed to without producing distracting shadows. Even on its brightest setting, the light isn’t overbearing, so it’s not too distracting to use for video calls.

This is a bright LED light that has a cold shoe mount for a camera, a tripod mount and a magnetic back to attach to other surfaces, but it isn’t easily usable with a phone, and you’ll have to supply a small tripod to use it with a laptop. Meant more for serious photographers, the light itself is hard to set up, uses a proprietary charger as opposed to a standard USB charger, is overwhelmingly bright and is expensive to boot.

The focal length of a lens defines the AFOV. For a given sensor size, the shorter the focal length, the wider the AFOV. Additionally, the shorter the focal length of the lens, the shorter the distance needed to obtain the same FOV compared to a longer focal length lens. For a simple, thin convex lens, the focal length is the distance from the back surface of the lens to the plane of the image formed of an object placed infinitely far in front of the lens. From this definition, it can be shown that the AFOV of a lens is related to the focal length (Equation 1), where $ \small{f} $ is the focal length and $ \small{H} $ is the sensor size (Figure 1).

The EMart comes with two phone holders. One of them is quite handy, clipping onto the thinnest part of the tripod stand with a small metal clasp that wraps around the pole; it can hold your phone vertically or horizontally. The second phone holder is a tripod mount, which means to use it with the EMart you’ll need a second tripod or stand since the ring light itself also uses the tripod as a light stand. We would have preferred to see a single mount that let you place both the phone and the light on the tripod mount, positioning the phone in the center of the ring. This isn’t a deal breaker since the other phone holder gives you plenty of options, but it is annoying nonetheless.

Be aware that Equation 6 is an approximation and will rapidly deteriorate for magnifications greater than 0.1 or for short WDs. For magnifications beyond 0.1, either a fixed magnification lens or computer simulations (e.g. Zemax) with the appropriate lens model should be used. For the same reasons, lens calculators commonly found on the internet should only be used for reference. When in doubt, consult a lens specification table.

Still, for just $16.99, the Whellen’s multiple light settings and ease of use make it one of the best ring lights out there — especially if you’re looking for something portable.

If the required magnification is already known and the WD is constrained, Equation 3 can be rearranged (replacing $ \small{ \tfrac{H}{\text{FOV}}} $ with magnification) and used to determine an appropriate fixed focal length lens, as shown in Equation 6.

Knowledge Center/ Application Notes/ Imaging Application Notes/ Understanding Focal Length and Field of View

Ring lights are available in many sizes and setups, from DSLR-friendly models meant to be mounted on tripods or light stands to miniature versions you can stick to smartphones, so over the course of a month we tested eight top-rated ring lights to determine which provided the best overall lighting for everyday users, with two taking top honors.

A fixed focal length lens, also known as a conventional or entocentric lens, is a lens with a fixed angular field of view (AFOV). By focusing the lens for different working distances (WDs), differently sized field of view (FOV) can be obtained, though the viewing angle is constant. AFOV is typically specified as the full angle (in degrees) associated with the horizontal dimension (width) of the sensor that the lens is to be used with.

In general, however, the focal length is measured from the rear principal plane, rarely located at the mechanical back of an imaging lens; this is one of the reasons why WDs calculated using paraxial equations are only approximations and the mechanical design of a system should only be laid out using data produced by computer simulation or data taken from lens specification tables. Paraxial calculations, as from lens calculators, are a good starting point to speed the lens selection process, but the numerical values produced should be used with caution.

While it may be convenient to have a very wide AFOV, there are some negatives to consider. First, the level of distortion that is associated with some short focal length lenses can greatly influence the actual AFOV and can cause variations in the angle with respect to WD due to distortion. Next, short focal length lenses generally struggle to obtain the highest level of performance when compared against longer focal length options (see Best Practice #3 in Best Practices for Better Imaging). Additionally, short focal length lenses can have difficulties covering medium to large sensor sizes, which can limit their usability, as discussed in Relative Illumination, Roll-Off, and Vignetting.

Note: Horizontal FOV is typically used in discussions of FOV as a matter of convenience, but the sensor aspect ratio (ratio of a sensor’s width to its height) must be taken into account to ensure that the entire object fits into the image where the aspect ratio is used as a fraction (e.g. 4:3 = 4/3), Equation 7.