August 27th, 2015

Assess Scope Optical Performance Using ScopeCalc.com

ScopeCalc.com

Zeiss DiavariHunters and tactical shooters need scopes with good low-light performance. For a scope to perform well at dawn and dusk, it needs good light transmission, plus a reasonably large exit pupil to make maximum use of your eye’s light processing ability. And generally speaking, the bigger the front objective, the better the low-light performance, other factors being equal. Given these basic principles, how can we quickly evaluate the low-light performance of different makes and models of scopes?

Here’s the answer: ScopeCalc.com offers a FREE web-based Low-Light Performance Calculator that lets you compare the light gain, perceived brightness, and overall low-light performance of various optics. Using this scope comparison tool is pretty easy — just input the magnification, objective diameter, exit pupil size, and light transmission ratio. If the scope’s manufacturer doesn’t publish an exit pupil size, then divide the objective diameter in millimeters by the magnification level. For example a 20-power scope with a 40mm objective should have a 2mm exit pupil. For most premium scopes, light transmission rates are typically 90% or better (averaged across the visible spectrum). However, not many manufacturers publish this data, so you may have to dig a little.

ScopeCalc.com

ScopeCalc.com’s calculator can be used for a single scope, a pair of scopes, or multiple scopes. Once you’ve typed in the needed data, click “Calculate” and the program will produce comparison charts showing Light Gain, Perceived Brightness, and Low-Light Performance. Though the program is easy to use, and quickly generates comparative data, assessing scope brightness, as perceived by the human eye, is not a simple matter. You’ll want to read the annotations that appear below the generated charts. For example, ScopeCalc’s creators explain: “Perceived brightness is calculated as the cube root of the light gain, which is the basis for modern computer color space brightness scaling.”

Permalink Optics, Tech Tip No Comments »
January 20th, 2013

Vortex Optics Spotting Scopes and New FFP 2.5-10X for 2013

Having heard many good things about Vortex spotting scopes from our readers and Forum members, on Day 1 of SHOT Show we headed over to the Vortex Optics booth. On display was the entire line-up of Vortex Viper and Razor spotting scopes (both HD and non-HD), with objective diameters ranging from 50mm to 85mm. We know that the 85mm Razor HD has been very popular with our readers, as it offers excellent “bang for the buck”. This spotter runs $1599.00 complete with 20-60 power eyepiece. That’s about half the cost of the big name Euro-brand spotting scopes with comparable objectives. Making the Razor HD even more attractive this year is the availability of a new 18X/23X long-eye-relief eyepiece for Vortex’s flagship spotting scope.

Vortex PSD Viper FFP 2.5-10 scope

For 2013, Vortex has added much-requested 65mm and 50mm models to its Razor HD line of spotting scopes. This is good news for guys who prefer a lighter, more compact spotting scope, or who don’t need the extra light-gathering power of a big 85mm objective. The 65mm and 50mm Vortex Razor HD models should be available by mid-spring 2013, and they will be priced quite a bit lower than their 85mm big brother shown above.

Watch Video to See Vortex Spotting Scopes and NEW 2.5-10X FFP Tactical Scope

Watch Factory Video on Vortex Razor 85mm HD Spotting Scope


After reviewing Vortex’s spotting scopes, we checked out an all-new, compact first focal plane scope from Vortex that we predict will be very popular with three-gun and tactical shooters. The New Vortex Viper PSD 2.5-10x32mm tactical scope features an FFP design. This enables rapid ranging with the provided reticles at all magnification levels. This scope with be offered with mil-based clicks and EBR-1 milrad reticle, or with MOA-based clicks and a EBR-1 reticle with MOA-based subtensions. We were also pleased to learn that Vortex will add a 6-24x50mm model to its Viper HS riflescope line.

Vortex PSD Viper FFP 2.5-10 scope

Permalink New Product, Optics No Comments »
January 21st, 2011

SHOT Show Report: New Leupold 20-60x80mm Spotting Scope

Yes, bigger is better. Leupold has upgraded its popular “folded-light-path” compact spotting scope, by adding an HD-glass, 80mm front objective and boosting the magnification up to 60-power. That will give this NEW scope better low-light performance and higher magnification while retaining a usable exit pupil (if you increase magnification without increasing the front lens diameter, the exit pupil shrinks). The unit costs $1800, not bad considering the price of other 80mm spotters, and the Leupold is much easier to carry, given its compact design.

Bigger Objective, Better HD Glass, More Useful Magnification Range
We’ve always liked the Leupold compact spotter because it is light weight and it’s Newtonian (folded light path) design makes it much more compact than most spotters of comparable magnification. The U.S. Military currently uses the Mark 4 “tactical” version of the Leupold 12-40x60mm spotter. However, we felt that the glass in the 12-40 spotter was not on a par with the latest generation HD spotters from Kowa, Zeiss, and Leica, or even Nikon and Pentax for that matter. Leupold has taken a huge step forward by gracing its new spotter with a big, HD (low dispersion) front objective. This should give the scope better perceived sharpness with much less color fringing (chromatic aberration) when viewing targets at long range. Upsizing the objective to 80mm makes the scope brighter, improving low-light performance. That’s important, particularly for tactical guys and hunters. The bigger objective also allows Leupold to increase magnification all the way from 40X to 60X. Do you always want a 60-power view? No, but it is great have 50% more magnification on tap when you need it.

Leupold 20-60x80mm spotting scope

60X is a Good Thing for Target Shooters
Most 40-power spotting scopes struggle to resolve 6mm and 6.5mm bullet holes at 600 yards. With HD glass and 60X magnification, you’ll have a much better chance to see small bullet holes at long range (though you’ll also need good viewing conditions). That’s a huge advantage for the long-range target shooter. Overall, we were very pleased that Leupold engineered this much-enhanced 80mm spotter. We predict it will be a big hit with anyone who needs serious magnification in an easy-to-carry optic.

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