Roof Prism vs Porro Prism: Which Binoculars Are Better?

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When you’re picking out a pair of binoculars, it can be tempting to just find a good price and go with it. However, there are better ways to choose binoculars. Keep reading to find a pair that fits your needs.

Experienced birders need binoculars that will perform well under a variety of circumstances. You want to choose something that will let you get a clear look at faraway birds, but you likely want something lightweight and portable. Your binoculars need to be within your budget, but also need to be durable.

A factor that new birders often don’t consider is the kind of prism used on your binoculars. There are two options: roof prism and Porro prism. But which is the better option?

Let’s take a look at the differences between these two types of prisms and how to choose the best one.

What Are Prism Binoculars?

In a pair of binoculars, there are two lenses: the objective lens and the ocular lens, which is also called the eyepiece.

The eyepiece, as you can probably guess, is the end that you hold up to your eyes. The objective lens is situated at the opposite end of the binoculars.

In prism binoculars, both the ocular lenses and the objective lenses are convex, and between the two is the prism.

The prism lengthens the path between the two lenses. By lengthening the prism, you successfully increase the magnification without needing to make the binoculars longer.

The prism renders the inverted image upright. Without the prism, whatever you see through the binoculars would be upside-down, and clearly, that’s not an option.

What Is a Porro Prism?

Ignazio Porro invented the Porro prism during the 19th century in 1851.

When you pick up a pair of Porro prism binoculars, you will find objective tube lenses that are offset from the ocular lenses.

The mechanism includes a block of material in the shape of a right geometric prism with triangular end faces that are positioned at a right angle.

The light enters perpendicular to the entrance of the lens and is then reflected twice from the sloped faces before exiting again through the larger, rectangular-shaped face.

Typically, these are used in pairs, which is called a double Porro prism. The second prism is rotated 90 degrees from the first one, and the light passes through both prisms.

This way, the light is reflected four times, and the prism creates a longer distance between the objective and ocular lenses.

Porro prisms are arranged in a zig-zag shape, which means you can spot Porro prism binoculars without needing to read the specs. You’re not looking for a zig-zag, though. Rather, you’re looking for two binocular tubes that are offset from the eyepieces.

Think of an old-fashioned pair of binoculars and how they are wider than the space between your eyes. These are Porro prism binoculars that have enough room for the Porro mechanism inside the tubes.

Advantages of Porro Prism Binoculars

Porro prism binoculars were the only real option for birders until recent years. They have lost popularity with the advent of roof prism binoculars, but there are still some advantages to this choice of prisms, such as the following:

  • Porro prisms are relatively inexpensive, thanks to well-established and affordable technology
  • They provide clear reflection–the clarity is superior to roof prism binoculars
  • They offer a wider field of view (FOV)
  • They are great for casual birding

Drawbacks to Porro Prism Binoculars

With those benefits, there are also a few drawbacks. Let’s examine these below:

  • Porro prisms are less durable than the slim-lined roof prism options
  • They typically aren’t waterproof
  • They are less powerful than most roof prism binoculars
  • They are heavier, making them less portable

What Is a Roof Prism?

A roof prism, on the other hand, is made with two faces that meet at a 90-degree angle. It gets its name because it looks like the roof of a building.

The light enters and leaves the prism on the same plane, which means the roof prism design takes up less space than a Porro prism.

Do you know the sleeker, newer-looking binoculars that extend directly from the eyepiece to the ocular lens? Those are roof prism binoculars. They don’t have that easily recognizable zig-zig design of a Porro prism pair.

Advantages of Roof Prism Binoculars

The advantages of roof prism binoculars have caused this style to replace Porro binoculars as the most popular style on the market.

  • They are comfortable and much more lightweight than Porro prism binoculars
  • The prism allows for more powerful magnification
  • They are frequently designed to be waterproof
  • The durability increases because the design is simpler

Drawbacks of Roof Prism Binoculars

There are only a few minor drawbacks to roof prism, which are as follows:

  • They tend to be more expensive than their Porro prism counterparts
  • Some people prefer the vintage style over the sleeker roof-style choice of prisms

Which Type of Prism Is Best?

Young woman using binocular for bird watching

When you’re choosing a pair of binoculars, the decision between roof and Porro prism may not be the biggest factor. However, it’s helpful to know about these two different design styles and how they differ!

There really isn’t a way to say which prism type is best. However, there are circumstances that make Porro or roof prism lenses the best choice for you.

The questions below can help you determine the best pair of binoculars for you:

What Are You Using Your Binoculars For?

People use their binoculars for different purposes. Some people just want to have a pair at their kitchen window to get a closer look at birds in the yard, so they don’t need something super lightweight or durable. They don’t need high-end binoculars, because they just need something to strengthen their view.

These folks would do just fine with a Porro prism pair of binoculars. After all, they will provide great clarity and field of view without breaking the bank.

However, someone who uses their binoculars while hiking, canoeing, kayaking, or adventuring will probably look for a pair that is lighter weight and more durable.

These shoppers are also likely to need something that’s compact for easy packing and stronger in magnification.

What Is Your Price Range?

Everybody likes a deal! However, in the case of binoculars, the old saying rings true: you get what you pay for.

If you’re on a tight budget, you will probably have to sacrifice some features, like durability, portability, and optical qualities.

However, If you’re ready to make an expensive purchase, you can splurge on just about everything!

Porro prism binoculars are available at lower price points than roof prism. So, if you’re bargain hunting, I recommend going with the Porro prism.

How Important Is Clarity of Image?

It may seem obvious that people want to have clarity when they look through their binoculars, but this issue is actually pretty subjective.

Not long ago, my family and I were camping, and we had two different pairs of binoculars. I had a vintage pair of Porro prism binoculars, and my sister had one with a roof prism. We both had a great time using our binoculars to see birds, animals, and landscape features from a distance using our binoculars.

But when we needed to identify small details in our view? My Porro prism binoculars offered more clarity than her roof prism pair.

At the same time, once we needed to spot things that were very far away, mine didn’t offer as much magnification or optical qualities.

Roof Prism vs Porro Prism: What Really Matters

The most important thing when buying a pair of binoculars is knowing that you are going to use them!

Not everyone needs the same pair of binoculars. What works well for you might not work well for someone else, and that’s okay!

Binoculars make birding more enjoyable and exciting. Whether you choose a roof prism or a Porro prism set, just be sure to choose something that you will enjoy using.

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Liz Ranfeld

Liz Boltz Ranfeld is an independent educator and writer from Indiana. She lives on the edge of the woods with her husband, 2 kids, dogs, chickens, and hedgehog. One of the best things of living in rural Indiana is spotting hawks, pileated woodpeckers, hummingbirds, and other wild creatures. She enjoys hiking, canoeing, and gardening, and one of her personal heroes is the conservationist and birdwatcher Rosalie Barrow Edge, who paved the way for the protection of birds around the globe.