Posted: May 6, 2013, 3:00 p.m. PDT
Each time I encounter a binocular that breaks through the pack, I imagine there’s no way it will ever be surpassed because it’s just that good. Time and again, I’ve been proven wrong as innovations and improvements in glass and coatings tweak a little more light and resolution out of an optical system.
Birders receive the full benefit because — apart from a bird in the hand — a bird in the bush has never looked so good. Perhaps best of all, some of these improvements and features are slowly migrating into low- and mid-priced optics.
When I began working for an optics retail company more than a decade ago, the lingo was a little different. Prospective buyers — mostly birders — wanted to know if lenses were coated, fully coated, multi-coated or fully multi-coated. They also wanted to know if prisms were BK7 or BaK4 and whether or not it was phase-corrected.
A hydrophobic lens coating is designed to keep water, dust and skin oils from adhering to the lenses.
It’s rare to hear this particular terminology today, because most birding binoculars have all of these things. Here, I aim to guide you through some of the more recent innovations in glass and coatings plus how these features can enhance your birding experiences in the field.
Hydrophobic Lens Coatings
As the name implies, a hydrophobic lens coating repels water. This is one of my favorite recent innovations. While more of a protective feature, it can prolong the integrity of the glass, but there’s more.
Not only do hydrophobic lens coatings bead and repel moisture, they also prevent buildup of dirt, dust, skin oils and other particulate matter on your lenses. This invisible coating has the added advantage of making lenses considerably easier to clean and less susceptible to becoming scratched; less cleaning means fewer chances of damage to the lenses. Also, when you wipe lenses with a cleaning cloth, it won’t leave streaks that can compromise your view. In the long run, your optics will maintain their brilliance and light and transmission efficiency longer than lenses without this protective coating.
Though not a proprietary technology, manufacturers typically give hydrophobic lens coatings their own brand name, so you might have to check specifications carefully when selecting binoculars and spotting scopes to make sure your desired models have the coatings. The binocular I use today has this coating, and it amazes me how little effort it takes to clean the lenses.
Less Expensive Optics with ED Glass
Have you noticed that annoying green or purple glow in areas of contrast when using your optics? It’s a type of optical distortion called chromatic aberration. Extra-low dispersion glass helps significantly diminish green or purple color fringing.
Binoculars and spotting scopes without ED glass will suffer from a lack of resolution, because the fringing distorts details. It’s less noticeable in the center of the field of view, but it still can be distracting when present in the periphery.
Fortunately, more low- to mid-priced optics are available with some type of ED glass. As with most other facets of optical glass, no two brands with ED glass will necessarily render the same color. You can’t expect a $300 binocular with ED glass to offer the same level of optical quality that a $2,000 binocular will provide. That said, it’s always better to have ED than not.
Dielectric Prism Coatings
We’re seeing mid-priced binoculars and spotting scopes with dielectric prism coatings. This optical coating increases brightness for low-light birding at dawn and dusk or in a dense forest.
You’ll also observe more faithful color reproduction and increased contrast. How much brighter? Dielectric coatings are marginally better than silver coatings but have as much as 8 percent improved reflectivity over aluminum coatings, so most birders are likely appreciate the difference.
A field flattener produces an optical field virtually free of edge distortion. When you look through the binocular or spotting scope, it will show almost perfect edge-to-edge sharpness instead of a sweet spot in the center with blurry edges.
Though optical field flattener lenses have been around for years, we’re beginning to see them in popular alpha-class optics. They can be found in some less expensive binoculars and spotting scopes, too. This lens system has an interesting quirk: When panning horizontally, you might perceive a "rolling globe” effect where the moving image appears curved, rolling with the center moving faster than the edges, hence the name. Interestingly, due to variability in individual eyesight, some people are more sensitive to this effect than others. As someone who has used a binocular with a field flattener for more than a year, I observed the rolling globe effect during the first weeks, but my eyesight seems to have adapted to it and I no longer perceive it.
Some opine that perfect edge-to-edge sharpness isn’t necessary, because you’re supposed to keep your line of vision in the center of the optical field. In other words, you don’t dart your vision around the field but move the binocular left, right, up or down when you want to change what you’re looking at, always keeping your vision fixed in the center.
Beginner Birder & Alpha-Class Optics
There’s no doubt in my mind that alpha-class binoculars and spotting scopes are advanced only in the sense that they’re expensive. Many birders think someone ought to be a seasoned birder before making a big financial commitment on a $2,000 binocular or scope; however, the better a binocular’s optical quality, the easier it is to make correctly identify birds — which benefits beginners.
New birders might struggle at bird identification while using inexpensive optics, but the good news is that options available today for less than $400 can rival the alpha-class binoculars of a decade ago. We’ve come a long way, and it’s hard for me to imagine better optics than the leaders of the pack right now, but I’ve been proven wrong before.