The classic design of porro prism binoculars is illustrated by these Bushnell Powerview 10x50 Binoculars. The Swarovski SLC 8x42 Binoculars provide an example of a popular roof prism design.

There are two primary types of binocular models – porro prism binoculars and roof prism binos. The objective lenses in porro prism binoculars are offset from the eyepieces – which gives them an angular, broader profile. The objective lenses in roof prism binoculars are straight in line with the eyepieces. Both types provide similar quality of viewing, so the ultimate questions may be: How do they feel in your hands? How does the balance feel? Can you comfortably reach and use the focus knob? How do they look? Today, many birders seem to prefer the sleek look and feel of roof prism binoculars.

You will be using your binoculars for many hours at a time, so make sure you buy the model that feels right for you. The first consideration may be to narrow your choice down to porro or roof prism models. It’s pretty easy to narrow it down quickly if you visit an optics or sporting goods store that has a selection of binoculars to handle. Try a couple models of each type, and see which feels better when you practice using it as you would use it in the field surrounded by a mixed-species flock of warblers. How does the balance feel? Is focusing smooth and easy?

Of course, there are a host of other considerations when trying out new binoculars, but if you get past the first step of choosing either a roof prism or porro prism model, you’ve already come a long way toward finding the best binocular for you. For a professional breakdown of binocular designs, including roof and porro prism models, refer the an excellent article at https://www.optics4birding.com/basics1.aspx