Convex Lens vs. Concave Lens: Decoding the Difference and What You Need

If you really think about it, the way lenses correct your vision is fascinating. Lenses blend light in various ways to help you see, and different people need different lenses to do the job. Enter convex and concave lenses.

These two types of lenses are essential for many people every day. We're delving into the difference between these two lenses and how they work. You'll also discover the many uses of these lenses beyond glasses and how to take care of them. We'll help you determine which type of lens you may need — although an optometrist will have the final say.

What Are the Basics of Optics?

Optics is a fascinating field of physics that deals with light and how it interacts with different materials, including lenses. Are you ready for a mini-physics lesson? We promise we'll make it quick.

One of the principles of optics is that light travels in straight lines (light rays) until it encounters an obstacle or a change. Once the light rays encounter something, they bend. Light can also reflect off surfaces, bouncing off at the same angle it hits the surface. These principles are the primary keys to understanding how light interacts with lenses, but let's go a little deeper.

How Does Light Interact with Lenses?

Refraction occurs when light bends passing through the lens. The lens is a change in the medium that allows this to happen. By bending the light, the lens can concentrate light rays and create images.

In summary, optics offers tools to understand light's behavior and how it interacts with the world around us, including lenses. With these concepts in mind, let's explore convex and concave lenses.

What Are Convex Lenses?

A convex lens, or covering lens, opens outward along the edges. It is thicker in the center and thinner at the top and bottom, which helps focus light rays on the retina. Imagine it like a little bump in the middle of your lens, directing the light rays where they need to go.

All parallel light rays passing through the lens meet at the same focal point. Therefore, even if the light passes through the top part of the lens, it will bend slightly down to meet the same point as light coming through the bottom part of the lens.

The convex lens's design allows for the formation of images, which are inverted and magnified. The degree to which the images are magnified depends on the focal length, which is the distance between the lens and the focal point.

There are three types of convex lenses: plano-convex, double convex, and concave-convex lenses.

Plano-Convex Lenses

Plano-convex lenses have one flat and one spherical surface (hence the name). These lenses are made for infinite parallel light use. The flat side serves as a starting line for incoming light rays.

When light rays pass through the lens, they encounter the flat surface, which helps to orient them and keep them on track as they move through the lens. The curved side ensures the light rays converge at the focal point to form an image.

Double Convex Lenses

A double convex lens, also known as a bi-convex lens, has two sides that are bent outward. This lens type has a shorter focal length than the plano-convex lens. The lens creates a virtual image for the eye but an actual image when used for photography.

Concave-Convex Lenses

The last type of convex lens is a concave-convex lens. One side is curved inward, and the other side goes outward. It's a combination of two different types of lenses. This lens is used to correct spherical aberrations of different lenses. This lens can also direct a laser beam.

What Are Concave Lenses?

As the name suggests, concave lenses curve inwards — think shallow bowl. They are the exact opposite of convex lenses. The edges of the lens are thicker than the middle. Instead of bringing light rays to the same focal point, they spread them out.

This divergence occurs because of the lens's curved surface. It causes the light rays to bend away from each other. Diverging the light allows for the formation of virtual images that look smaller and upright.

These lenses are essential for correcting certain vision problems. Nearsighted people need concave lenses to see correctly. Myopia, or nearsightedness, occurs when the eyeball is too long, or the cornea is too curved. The result of having these eyes is the light passing through blur's distant images. Almost 30% of Americans are nearsighted.

It isn't known what causes myopia, but evidence suggests people inherit it. If both parents have nearsightedness, their children are more likely to have it as well. The development of myopia can also be impacted by how someone uses their eyes. For example, people who spend a lot of time reading, working on a computer, or playing video games may be more likely to develop nearsightedness.

Studies have shown that a lot of screen time on smart devices is associated with a 30% higher risk of myopia. The chances of developing myopia jump to about 80% when you spend a lot of time on your devices (phone, tablet, etc.) and your computer. So, don't say you haven't been warned. But we know how hard it is to avoid a little screen time.

There are different types of concave lenses, similar to convex lenses.

Double Concave Lenses

The double concave or bi-concave lens features two inward curved surfaces. The lens can increase focal length, and the curvature and thickness of the lens can be adjusted to fit an individual's prescription.

Plano-Concave Lenses

Plano-concave lenses have one flat surface and one concave surface. They have a negative focal length and can help project the light.

Convex-Concave Lenses

For a brief review, this type of lens features both a convex and concave style lens. The convex side does have a higher curvature than the concave side. This design allows the lens to be the thickest in the center.

How Are Convex Lenses Used?

Eyeglasses are one of the major uses for convex lenses. However, these lenses can do more than just help people see.

Cameras

Certain cameras use convex lenses to focus and magnify images. The camera's magnification can be adjusted by repositioning the convex lenses. You can find these lenses in video cameras, webcams, and more.

Peepholes

Have you ever looked through a tiny peephole and wondered how you can see so much on the other side? This phenomenon actually takes both types of lenses. The convex lens is the lens on the inside of the door, and it helps focus your vision.

Microscopes

Microscopes are used to get an up-close look at objects too small for the naked eye. It takes three convex lenses in a microscope to enlarge these objects. There are microscopes with additional lenses that can magnify microbes even more.

Magnifying Glass

If you've ever seen someone try to start a fire with a magnifying glass, you know it works by concentrating a sunbeam on kindling. It takes patience, but eventually, there's smoke and then fire. The convex lens's ability to focus the incoming light onto one focal point allows for the kindling to heat up. It also magnifies objects when looking through the glass.

Projectors

A projector can project images from a small piece of film onto a large area. The convex lens helps the projector create an enlarged and flipped image, which is why the film is uploaded upside down.

Refracting Telescopes

If you ever want to get a closer look at the moon or stars, you'll need a telescope. A telescope can give you a view of objects very far away. One type of telescope is a refracting telescope, which uses two convex lenses. One of the lenses works to combine all of the light rays, while the other magnifies the image.

Convex Mirrors

While mirrors are obviously not lenses, it may be easier to grasp the convex concept by looking at curved mirrors. Convex mirrors, or diverging mirrors, bulge out, and light creates a virtual image smaller than the object.

These virtual images offer a much larger view than plane mirrors. There are many different uses for this type of mirror.

• Vehicle rear-view mirrors
• Inside parking garages
• Security inside large places, like malls

Start looking for convex mirrors the next time you're out and about. We bet you'll start noticing them everywhere.

How Are Concave Lenses Used?

There are just as many uses for concave lenses as there are for convex lenses. Let's go over how these lenses are put to use.

Lasers

Concave lenses are essential in lasers. Consider how many things use lasers, medical equipment, scanners, and much more. The lenses disperse the laser, allowing equipment to work correctly. The small concave lenses widen the laser beam to target a specific area.

Cameras

Cameras use both concave and convex lenses. Concave lenses can help improve a photograph's quality by eliminating chromatic aberrations caused by convex lenses. The convex lens can't always focus on all the colors of light at the same point, which causes color fringing in photos. The addition of the concave lens can cancel out this problem.

Peepholes

Concave lenses are used on the outer section of peepholes. The lens enlarges the image on the other side of the door, so you'll know what you're opening your door to.

Flashlights

Concave lenses spread light, making them perfect for flashlights. Light passes through the hollowed side of the lens and is dispersed on the opposite side. The lens increases the radius of the light exponentially.

Concave Mirror

A concave mirror, or converging mirror, is shaped inward away from the light source. This type of mirror converges or focuses the light rays.

Concave mirrors can form various images depending on the distance between the mirror and the object.

Here are some common uses for concave mirrors:

• Shaving mirrors
• Head mirrors, like the ones optometrists use
• Ophthalmoscope
• Astronomical Telescopes

Do You Need Concave or Convex Lenses?

After reading the descriptions of both lenses, you may already have a pretty good idea of which type you need. However, optometrists can determine exactly which type is right for you.

You may benefit from concave lenses if you are nearsighted (myopic) and struggle to see objects at a distance. You may need convex lenses if you're on the opposite side of the spectrum and can't see objects up close.

If you've got your vision covered, you may be looking for the right lens for a camera:

• Concave lenses can capture wide-angle views and panoramic images. They spread out light rays and allow for a broader field of view.
• Convex lenses can magnify images and bring faraway objects into focus — their ability to combine light rays results in magnified and clearer images.

Ultimately, the lens you need depends on your needs and the desired outcome.

What To Consider When Choosing Lenses

When it's time to get new lenses and maybe some stylish frames to go with them, there are a few things to consider. Selecting high-quality lenses will make a world of difference. But how do you choose with so many options available?

Here are some key factors to help you make the best decision:

Optical Quality

The quality of the lenses is the most important aspect to consider. Find convex or concave lenses made from high-quality materials and manufactured with precision to ensure optimal clarity and minimal distortion. Pay attention to lens coatings, which can impact image quality.

Pair Eyewear uses a state-of-the-art lens lab to produce an Rx option to correct vision for a single distance, whether you are nearsighted, farsighted, or have astigmatism. Our lenses produce optical powers from -14.5D to +5.00D, which addresses the prism, sphere, axis, and cylinder. In addition, they are treated with anti-reflective and anti-scratch treatments so you can always see clearly.

Cost and Availability

How much you want to spend on your new glasses also plays a significant role in lens selection. This factor is particularly important for those with limited finances.

Figure out how much you can budget for new lenses and explore options within your price range. While some higher-priced lenses offer superior performance, many affordable alternatives are still great options.

When ordering specialized eyewear, make sure what you need is readily available. If you're ordering online, remember to account for shipping times.

Experience

Consider the overall experience when selecting a lens. Do you like the design and look of the eyewear? You can test out different pairs to find the perfect fit.

What Should You Know About Lens Maintenance and Care?

Taking care of your new lenses is key to making them last. The worst thing is having to use glasses that have been scratched or damaged. Follow these tips and tricks to keep your lenses in tip-top shape.

How To Clean Your Lenses

Regular cleaning is essential to remove oil, dirt, fingerprints, and other debris. However, it's important to be careful because 80% of lens scratches happen when eyewear is cleaned incorrectly.

Follow these steps to clean your lenses:

1. Start by rinsing off your lenses with warm water and any mild soap. Make sure the soap doesn't have any additives. You can also use approved lens cleaning solutions. Avoid chemicals like glass cleaner because they can damage the coating on your lenses.
2. Next, dry off your glasses with a microfiber or soft, lint-free cloth. You can also use lens wipes, but avoid anything not made for optical surfaces, as they can hurt the lens coatings.
3. Apply a small amount of cleaning solution and wipe the lenses in a circular motion to remove any stubborn smudges. Avoid using too much pressure.
4. If you still notice marks on your glasses, repeat the cleaning process as needed. The marks may be small scratches on the lens.

Pair Eyewear covers you if you scratch or damage your lenses or frames. We provide complete protection when you add the one-year warranty to your order.

Storage

Protecting your lenses is important when you're not wearing them. Always keep your glasses in a clean, dry environment. Moisture and extreme temperatures can lead to issues. Don't place two pairs of glasses into the same case without dividers. The separation will keep them from getting scratched.

Handling

You may be able to throw your cheap sunglasses in a bag or lose them amongst your things, but prescription glasses should be handled with care. Avoid touching the lenses as it can transfer oils, dirt, and moisture. Hold your glasses by the frame and never on the lenses. No one wants to look through fingerprints.

What Are Some Glasses Recommendations To Correct Your Vision?

Finding new glasses can feel overwhelming with so many options available. Thankfully, we've got you covered. One of the best parts about Pair Eyewear is the variety available with our Top Frames.

Our Top Frames snap on magnetically to the front of your Base Frame — it's an easy way to switch up your look and change the color of your frames. Our frames are made from hand-polished, flexible, and durable acetate.

Here are a few styles to check out and what face shape they'll look ideal on:

• The Kirby: This style is one of our best sellers. It's a medium rectangle frame that is always stylish and timeless. This frame shape looks great on anyone but particularly suits oval or round face shapes.

• The Reese: The Reese is a narrow, modified round frame ideal for oval, square, or diamond-shaped faces. You can pick a basic base color and wear these Top Frames when you're in the mood to add a little sparkle to your life.

• The Drew: This is a dynamic extra-wide rectangle frame. They fit an oval, round, or triangle face shape. Don't let the face shape hold you back if they look good on most.

• The Finley: The Finley frames are another one of our best sellers. They are a narrow rectangle frame that will make you look effortlessly cool. This frame shape fits an oval or round face. Add a sun top to transform them into sunglasses.

Pair Eyewear offers many different Base Frames and corresponding Top Frames for women, men, and children. They can all come with lenses to correct near or farsightedness.

Lenses For All

Everyone's vision is different, and some require help to see things clearly. Convex lenses are for farsighted people, while concave lenses help those who are nearsighted. No matter what your vision needs are, Pair Eyewear has what you need for crystal-clear eyesight and a fashionable appearance.

Sources:

Video of Learn how different lenses form images by refracting light | Britannica

Myopia (nearsightedness) | AOA

Nearsightedness - Symptoms and causes | Mayo Clinic

Farsightedness (Hyperopia) | National Eye Institute

Proper Lens Care Instructions | Evansville Eye Care Associates