"Be careful though...90% of sales staffs can mislead with uneducated suggestions and hear-say on optical specs and recommendations."
90%!? The eternal optimist. I rush on to say most do this with no malice in mind. It’s just they don’t know, their bosses don’t know enough to train them, and most of the info in magazines and on the net drips with erroneous information. Example ahead:
Enter The Experts
Magazines offering an aura of fidelity often rely on their own stable of experts who, when it comes to optics, may not be experts at all. Instead, these freelancers may write about car stereos on Monday, fishing gear on Wednesday, and the best pizza in town on Friday. There’s no doubt if they offer truthful opinions about what they like and what they don’t, those opinions can be worthwhile. Still, when it comes to understanding more than a few basic buzzwords and phrases, which have been circulating for decades, being a master birder, serious amateur astronomer, or seasoned hunter or mariner makes a person no more of an expert on binoculars and optics than being a disk jockey makes one an expert on the design, manufacture, and performance of microphones.
Following are some examples found in influential sailing magazines. Birding, hunting, and amateur astronomy magazines are just as prone to have serious errors. Being with Captain’s Nautical Supplies at the time these were just more prominent.
1) “In the loosest sense, ‘marine’ binoculars simply means ‘waterproof,’ which means they have some sort of rubber armoring.”
Not so! Many inexpensive, rubber armored “marine” binoculars have little or no waterproof/fog proof integrity. On the overleaf from that comment was a comparative chart stating a certain binocular was “nitrogen filled,” implying gas tight/watertight integrity. In reality the binocular was an inexpensive center-focus model with two-piece body styling not even promoted as waterproof by the manufacturer or importer and incapable of holding a nitrogen charge. Did the writer make up that part to add a few words to the article or did he or she just interview the company’s representative who knew a great deal about sales and not so much about binoculars?
Another read:
2) “Center-focus models have a speed advantage over individual-focus models, but don’t compensate for varying eye strengths.”
That’s so wrong it should have been an embarrassment to the writer and the editor. Of course they compensate for “varying eye strengths”; that’s what focus mechanisms do, whether on center-focus or individual-focus instruments.
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A center-focus and Individual-focus binocular
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Finally:
3) “Porro prisms are used in most marine binoculars because they provide greater depth of field than roof prisms.”
This faulty passage only touches on a half-truth as the lines between depth of field and a 3-D effect become blurred. Do marine binoculars employ Porro prisms? Yes, most do. Do those binoculars provide a greater 3-D effect than their roof prism cousins? Over a relatively shallow distance, yes. Even so, the type of prism is only responsible in a peripheral way.
Because of the size and configuration of Porro prism clusters or mountings, the telescopes must be spaced farther apart. This spacing is what creates the stereoscopic view that produces the illusion of depth; the prism type has nothing to do with it. Even so, this 3-D effect diminishes with distance and is appreciated more by the naturalist and hunter than the mariner, whose targets are usually at greater distances, and considerably more than the amateur astronomer whose targets are seen at infinity.
A binocular, telescope, or camera can only be focused precisely on one object or plane at a time. Before or after that distance images will grow gradually more defocussed. The range in which the observer can appreciate a seemingly focused image constitutes the depth-of-field. Clinically, this term relates to monocular vision. However, the 3-D effect created by the visual cortex of the brain is widely accepted as depth-of-field as opposed to depth perception.
From Wikipedia:
“Stereopsis was first explained by Charles Wheatstone in 1838: “… the mind perceives an object of three dimensions by means of the two dissimilar pictures projected by it on the two retinæ ….” He recognized that because each eye views the visual world from slightly different horizontal positions, each eye's image differs from the other. Objects at different distances from the eyes project images in the two eyes that differ in their horizontal positions, giving the depth cue of horizontal disparity, also known as retinal disparity and as binocular disparity. Wheatstone showed that this was an effective depth cue by creating the illusion of depth from flat pictures that differed only in horizontal disparity.”
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Photo, Illustration, or Comment Show a Porro prism cluster and how mounting creates the need for separation.
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So how do these things find their way into our regional and national magazines? Mark Twain asked a similar question of his publisher, William Dean Howells, who replied:
“Because paper never refuses ink.” (Attributed)
A Story: In early September 2015, someone in Orlando, Florida lost possession of his pet king cobra, “Elvis.” In October the 8-foot snake was captured hiding under a clothes dryer and certain people in the local media, including one television newscaster, announced the “kingsnake” had been found.
Although comparing a large, deadly king cobra to a small, non-poisonous kingsnake is like comparing a new Rolls-Royce to a used Volkswagen beetle, all those inexperienced or cranially challenged announcers and editors had the power to influence the unwary. And if such easy to find information can be that misunderstood and handled so carelessly by those we have come to trust, how much easier would it be for busy magazine writers and editors to misconstrue a topic as foreign to most as binocular optics?
Bill