Understanding Binoculars, Magnification and Objective Diameter

Understanding Binoculars - Bightness, Prisms, Contrast, Resolution

Understanding Binoculars - Exit Pupil,  Field of View, Eye Relief, Near Focus

Understanding Binoculars - Optical Coatings, Focusing

Understanding Objective Lens

All manufacturers clearly indicate magnification levels and the objective diameter of each of their binoculars in their product description. So when you see 15x50, 10x42 or 8x32 etc in the description of the binoculars the first number represents the level of magnification i.e. 15x, 10x or 8x and the second number represents the diameter of the objective lens i.e. 50mm, 42mm or 32mm.

Magnification is basically the number of times the binoculars will magnify an image so for example binoculars with 10x magnification will enlarge the image to 10x the size you would see it with the naked eye. The level of magnifying power will have an impact on how bright an image will appear so generally speaking binoculars with 8x magnification will deliver a brighter image than those with 10x magnification.  

The greater the magnification the more susceptible the binoculars are to distortion due to handshake. You will often see that the recommendation for bird watching binoculars is that you use 7x or 8x magnification, possibly 10x at the most (unless you are going to use a tripod). This is because binoculars over 10x magnification are likely to provide you with distorted vision due to slight movements in your hand.

If you are looking for high levels of magnification, without using a tripod, then there are binoculars on the market that include image stabilizing technology, at a price! Users of binoculars which incorporate image stabilizing technology rave about the clear sharp images they provide. High magnification binoculars can be hand held when they incorporate imaging stabilizing technology and images will remain sharp even in a moving vehicle.

If you are looking to use binoculars in a moving environment or need high levels of magnification (whilst hand held) take a look the Canon IS Binoculars or the Nikon StabilEyes.   

Objective lenses are the large lenses at the front of the binoculars through which the light passes through. Binoculars with larger objective diameters gather more light which will have a positive impact on image brightness. If you are looking for binoculars that are suitable for astronomy, for example, you need to be able to gather as much light as possible and will therefore need to look for binoculars with a large objective lens.

Doubling the size of the objective lens will mean the binoculars will have four times the light gathering ability but this benefit should be considered alongside other factors such as usage and the size of the exit pupil as part of your buying decision.

One of the main downsides of large objective diameters is the weight and size which is why lightweight, compact binoculars have smaller objective lenses. If you are looking for bird watching binoculars for example, that are to be hand held, you won’t want to go out and buy massively heavy binoculars with a large objective lens.

Bird Watching Binoculars / Astronomy Binoculars / Compact Binoculars

Understanding Binoculars cont.........