Choosing Binoculars

Of all the things I get asked about one of the most common things is Binoculars and what to choose.

If you are based in Norfolk UK don’t hesitate to contact Cley Spy – here’s their website https://www.cleyspy.co.uk/?_gl=1%2Asvux2j%2A_up%2AMQ..%2A_gs%2AMQ..&gclid=Cj0KCQiAi9rJBhCYARIsALyPDtv4k5aRknU9DjEY8x-maigfPVCPvew-OybOVjDvmcTiV1sgUMRsfqUaAvy_EALw_wcB&gbraid=0AAAAADfjjFtwu9Jih_mOgV1sH6b3M4V2Y– the staff there are brilliant and will work within your budget to give you something appropriate to your needs.

If you’re not based in Norfolk here are a few notes that may help you.

  • Price – can be anything from £100 to £2500
  • You will generally pay for what you get
  • Don’t discount a 2nd hand pair of binoculars
  • Try BEFORE you buy – Cley Spy is a good starting place
  • Magnification 8x or 10x most popular – 8x has wider field of view and is generally brighter
  • As one gets older 8x are easier to handle and hold steady
  • 8×42 binoculars – first number magnification, 2nd is diameter of objective lens in mm
  • Greater objective lens diameter, greater light gathering capacity
  • Exit pupil is diameter/magnification – this is diameter in mm of the exit beam of light into your eye. Anything above 8mm is wasted as this is the normal maximum pupil size
  • Poro Prism -v- Roof prism – roof prisms are lighter and more expensive – Poro’s usually give a wider field of view and a more 3D effect
  • Gas Filled binoculars are water proof and dust proof
  • Balancing binoculars – cover objective lens with dioptre (single barrel focussing wheel) fitted & focus on subject. Cover other objective lens and focus with dioptre adjustment on same subject – do not close either eye as closing one eye effects muscles in the other
  • Twilight Factor – Square root of Objective lens size x magnification – ie 10×40’s = 400 = 20, 8×42’s =336 =18.3 The higher the twilight factor the greater the resolution
  • Consider minimum focusing distance if you are viewing dragonflies and butterflies
  • Eye Cups – with spectacles put down without spectacles pull up – but this is very much a personal preference
  • The general feel must be good – very much a personal choice
  • Straps must be wide – consider using a harness if uncomfortable
  • Choose a good rain guard that falls out of the way when you raise your binoculars
  • Clean lenses with a blower then a brush then a cloth with an alcohol cleaner
  • Protect the coatings they do the heavy lifting regarding light transmission to your eye