The larger the objective, the more light the binocular will gather. Porro Prism Design - A system in which two separate prisms are positioned in an offset relationship so that there is greater separation between the objective lenses than the eyepiece lenses. Prisms - Binoculars use convex lenses for both the objective lens and ocular lens, which results in an image that appears upside down and backwards. But Pentax puts a seven-layer coating on all optical surfaces. This means more available light is transmitted to your eye.
Glare is reduced and image contrast is enhanced.
The two most popular designs used to make modern binoculars are based on porro prisms and roof prisms. The prisms in binoculars correct the upside down and reversed image you would see without them. The roof prism design allows each barrel to be straight. Let's look at the advantages and disadvantages of porro prism vs. roof prism design Porro Prism Design Advantages - Less expensive. Good optical quality.