Thread: Sheep Hunting
View Single Post
  #51  
Old 06-16-2018, 07:17 AM
sillyak sillyak is offline
 
Join Date: Jul 2009
Location: Lacombe, AB
Posts: 1,404
Default

Also, I wouldn't get too worked up over HD marketing when it comes to binos or spotting scopes.

HD or ED marketing in optics means extra low dispersion glass. When light travels through glass the different wavelengths of light refract in different amounts so different colours focus at different points. This means when you focus on something, the far ends of the spectrum (Red and Purple) are not in good focus (chromatic aberation). This leads to the purple and orange fringes seen around bright objects and reduced sharpness over the whole image.

ED glass helps greatly to correct this and allows all wavelengths to come to sharp focus at a similair point (no glass is perfect, but some are pretty darn close).

However not all ED glass is created equal. FPL 51, 53 and 55, FCD 100, FK-61, real Fluorite crystal ect. are all marketed as "ED" and some are definitely better than others. Also, optical design plays a huge role in colour correction (the best glass in the world isn't overly good if the design isn't up to snuff or if other glass components like the prisim or eyepiece are inferior.) Remember the ED element is a single piece of glass in the objective. There are minimum 5 glass elements per side, it's not just the one ED element that matters. Mechanics also play a huge part in binoculars quality.

So in short: ED glass is great, but it's not everything. Test as many pairs of binoculars as much as possible before buying; and don't commit yourself to a pair based on marketing.
Reply With Quote