Rifle Scopes What makes a scope "High Definition"?

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Minuteman
Feb 15, 2010
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New guy here. I've been wearing out the search function as I spin up but haven't been able to find info on what makes a scope "High Definition". Is there a measurable parameter like, say, diffraction limited @ wavelength X? Or is it more along the lines of someone looking through it and deciding the image is crisper than usual so it's called HD? Input welcome.
 
Re: What makes a scope "High Definition"?

HD is actually a low dispersion glass and coating.....although some people may call it high def. It kinda does that. It's same as the "ED" some photographic lenses are labeled with. A different glass and improved coating. It filters the light better so to speak....keeps the scattering of photons under control and creates better contrast. The quality we call image sharpness is often times just improved contrast....and the human eye sees it as sharpness.
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Re: What makes a scope "High Definition"?

HD is "high definition" (not high dispersion, which is just the opposite). AFAIK it's the same as "ED" and "APO" - the use of fluorite crytal lenses or fluoridated glass to achieve low color separation ("finging")in long lenses. You get less color fringing so objects appear to be sharper - kinda like HDTV!
 
Re: What makes a scope "High Definition"?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: One-Eyed Jack</div><div class="ubbcode-body">HD is "high definition" (not high dispersion, which is just the opposite). AFAIK it's the same as "ED" and "APO" - the use of fluorite crytal lenses or fluoridated glass to achieve low color separation ("finging")in long lenses. You get less color fringing so objects appear to be sharper - kinda like HDTV! </div></div>

Funny...my screw up....yes thanks...for the correction. I misspoke. It has been years.... . Calcium fluoride or "fluorite crystals" were used to produce LD glass and ELD glass (extra low dispersion)at one time. Spherical aberration and fragility problems reared their head with the fluorite...new glass was developed by Leitz if I remember right....but...another story. It's all techno babble anyway. Buy good equipment!!!
 
Re: What makes a scope "High Definition"?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: The new guy</div><div class="ubbcode-body">I'm the new guy thank you very much. </div></div>

Naw, you're just <span style="font-weight: bold">a</span> new guy; we come in 18-packs...
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Interpreting One Eye's reply to technobabble: HD glass is a material whose index of refraction has low dependency on wavelength. Is there a recognized manufacturer measurement(s) which deliniates HD from non-HD? Just curious if it's a technical or marketing term. It won't have any bearing on my scope decision except to perhaps indicate a better than usual image in its class. Thanks for the replies.