Porro Prism vs Roof Prism Binoculars: Which is Best?

Last Updated: by: Robert Sparks

porro prism vs roof prism binoculars

What is a Prism?

A prism can be made from any transparent object, but in optics they are most commonly made of glass.  The simplest prisms are triangular and must have at least two smooth faces at acute angles.  These angles create a color spectrum by absorbing and dispersing light.  Prisms in optics lengthen the light path from the objective lens to the eyepiece, increasing magnification without increasing the binocular tube length.  Optics are typically made with BAK4 prisms, a German-invented glass that improves refraction.  They create an optimal amount of light travelling through your binoculars and into your eyepiece.

Related reads: Guide on choosing the right pair of binoculars for your needs

The Porro Prism

Porro prisms, named for Italian inventor Ignazio Porro, consist of two right-angled prisms facing each other.  In a Porro prism device, the eyepiece is not in line with the objective lens, so the prism must jag the light sideways in its path across the two prisms.  Binoculars were originally built this way to increase the pathway length of the light and optimize image quality.

Bushnell H2O Porro Prism Binocular

The Bushnell H2O is an example of a porro prism binocular

The Roof Prism

Different styles of roof prisms can be found in binoculars, but the most common types are the Abbe-Koenig and the Schmidt-Pechan.  The Abbe-Koenig is comprised of two connected prisms that form a V-shape.  When light enters the prism, it bounces across several angles before exiting through the opposite side, extending the light’s path.  Schmidt-Pechan prisms are slightly more compact.  They are also constructed of two prisms, but these are separated by a slight air gap.  The unusual angled shape of the Schmidt-Pechan means the light path can travel longer than the Abbe-Koenig prism, improving brightness and light absorption.

Vortex Optics Diamondback Roof Prism Binoculars

The Vortex Optics Diamondback is an example of a roof prism binocular.

The Pros and Cons

Porro Prism Binoculars

Pros

The wide spread of the objective lenses and the simplicity of the light path inside make Porro prism binoculars superior in clarity and depth perception.  They also provide a wider field of view.  Most users find overall better image quality with Porro binoculars.

  • Superior in clarity
  • Better depth perception
  • Wider field of view (FOV)
  • Overall improved image quality
Cons

Because Porro prism binoculars have an awkward shape, they are bulkier and heavier than their roof prism counterparts.  It is also more difficult to find waterproofing in Porro prism models.  Both factors contribute to a decrease in overall durability in comparison to roof prism devices.

  • More bulk and weight
  • Less waterproofing quality
  • Lower durability

Roof Prism Binoculars

Pros

Because the tube in a roof prism binocular is straight, you get a slimmer, more streamlined design.  This makes them more durable, as well, as their engineering is simpler.  You also achieve better magnification strength with roof prisms.

  • More durability
  • Lighter weight
  • More compact
  • Superior waterproofing
  • Better magnification strength
Cons

You may lose some clarity with roof prisms, and the narrower field of view can be a setback for some.  Roof prisms are also costlier to manufacture, which means you’ll notice a significant jump in price compared to Porro prism devices.

  • Slightly less clarity
  • Narrower field of view (FOV)
  • More expensive

The Price

While you can find a decent pair of Porro prism binoculars for under $100, you’re more likely to pay between $100 to $200 for a good quality device.  If you want a decent pair of roof prism binoculars, however, plan to spend between $200 to $1000 dollars on average.

The Decision

If you’re planning to do your glassing in heavily forested areas or other places where obstacles are close, you may want to choose Porro prism binoculars.  You’ll get a wider field of view and better clarity within your glassing range for less money.  This is ideal for birders and hunters.  For longer-range wildlife watching or stargazing, you’ll want more magnification.  If you fall in this category, the higher power range of the roof prism style will suit you better.  But you’re likely to find a great pair of binoculars in either style.  Just remember to consider your budget and what you’ll be glassing before you purchase.

Related Reads: What’s the difference between the popular Vortex Crossfire and Diamondback Binoculars?