September 22nd, 2017

Seeing Bullet Holes at 1000 Yards — the Ultimate Optics Challenge

Pentax PF 100ED

Pentax smc-xw 10mmWhile attending the CA Long Range Championship a few seasons back, we had the opportunity to test the performance of a high-magnification (63X) spotting scope in near-ideal conditions (maybe the best I’ve ever witnessed). On the event’s last day we arrived at 5:45 am, literally as the sun was cresting the horizon. I quickly deployed our Pentax PF-100ED spotting scope, fitted with a Pentax SMC-XW 10mm fixed-power eyepiece. When used with the 100mm Pentax scope, this 10mm eyepiece yields 63X magnification. Befitting its $359.00 price, this eyepiece is extremely clear and sharp.

At the crack of dawn, viewing conditions were ideal. No mist, no mirage, no wind. The first thing this Editor noticed was that I could see metal nail heads on the target boards. That was astonishing. As soon as the first practice targets went up, to my surprise, I could see 6.5mm, 7mm, and 30-caliber bullet holes in the white at 1000 yards. No lie…

That’s right, I could see bullet holes at 1000. I know many of you folks may not believe that, but there was no mistaking when I saw a 7mm bullet cut the white line separating the Nine Ring and Eight Ring on the target in view. (I was watching that target as the shot was fired and saw the shot-hole form). And when I looked at the 30-cal targets, the bullet holes in the white were quite visible. In these perfect conditions I could also make out 3/8″ bolt heads on the target frames.

The Human Factor
When viewing the bullet holes, I was using my left naked eye (no safety glasses or magnification). I also had a contact lens in my right eye (needed for distance vision). To my surprise, while I could see the bullet holes without much difficulty with my left eye, things were fuzzier and slightly more blurry with the right eye, even when I re-focused the scope.

Pentax smc-xw 10mmThen I invited 3 or 4 shooters to look through the scope. One younger guy, with good eyes, said immediately: “Yeah, I can see the holes — right there at 4 o’clock and seven o’clock. Wow.” Some older guys, who were wearing glasses, could not see the holes at all, no matter what we did to the scope’s main focus and diopter adjustment.

The lesson here — if you have to wear glasses or corrective contact lenses, just that extra bit of optical interference may make a difference in what you can see through the scope. Basically anything that goes between the scope eyepiece and your eyeball can degrade the image somewhat. So… you may be better off removing your glasses if you can still obtain good focus sharpness using the diopter adjustment and focus ring. I did the left vs. right eye test a half dozen times, and I could definitely see small features at 1000 yards with my naked eye that I could not see with my right eye fitted with a contact lens. (I did have to re-focus the scope for each eye, since one had a corrective lens while the other did not.)

Mirage Degrades Image Sharpness and Resolution
The “magic light” prevailed for only an hour or so, and then we started to get some mirage. As soon as the mirage appeared I was no longer able to see raw bullet holes, though I could still easily see black pasters on the black bulls. When the mirage started, the sharpness of the visible image degraded a huge amount. Where I could see bullet holes at dawn, by mid-morning I could barely read the numbers on the scoring rings. Lesson: If you want to test the ulimate resolution of your optics, you need perfect conditions.

Chromatic AberrationChromatic Aberration Revealed
As the light got brighter and the mirage increased I started to see blue and red fringing at the edges of the spotting disk and the large numerals. This was quite noticeable. On one side of the bright, white spotting disc you could see a dark red edge, while on the other side there was a blue edge (harder to see but still present).

The photo below was taken through the Pentax spotter lens using a point and shoot camera held up to the eyepiece. The sharpness of the Pentax was actually much better than this photo shows, but the through-the-lens image does clearly reveal the red and blue fringing. This fringing is caused by chromatic aberration — the failure of a lens to focus all colors to the same point. Chromatic aberration, most visible at high magnification, causes different wavelengths of light to have differing focal lengths (see diagram). Chromatic aberration manifests itself as “fringes” of color along boundaries that separate dark and bright parts of the image, because each color in the optical spectrum cannot be focused at a single common point on the optical axis. Keep in mind that the Pentax does have “ED” or low-dispersion glass, so the effect would be even more dramatic with a cheaper spotting scope.


CLICK HERE to view LARGE PHOTO that shows aberration more clearly.

If you wonder why top-of-the-line spotting scopes (such as the $3900 Leica APO-Televid 82) cost so much, the answer is that they will deliver even LESS chromatic aberration at long range and high magnification. With their exotic apochromatic (APO), ultra-low-dispersion glass, a few ultra-high-end spotting scopes can deliver an image without the color edging you see in the photo above.

The Pentax PF-100ED is a heck of a spotting scope. Any scope that can resolve bullet holes at 1000 yards is impressive. But if you want the ultimate in optical performance, with minimal chromatic aberration, you may need to step up to something like the 88mm Kowa Prominar TSN-883 with Flourite Crystal lenses ($2450.00 body only), or the 82mm Leica APO ($3899.00 with 25-50X eyepiece).

EDITOR’s NOTE: The purpose of this report is to show what is possible… in IDEAL conditions. With this Pentax 100mm, as well as a Swarovski 80mm, we have often been able to resolve 6mm bullet holes at 600 yards. But again, that performance requires really good viewing conditions. By 10:00 am at my range, even with the 100mm Pentax at 75 power, seeing 6mm bullet holes is “iffy” at best. So don’t go out and mortgage the house to buy a $4000 optic with the hope that you’ll be able to spot your shots at 1000 yards. If conditions are anything less than perfect, you’ll be lucky to see bullet holes at 500 yards. The real solution for very long-range spotting is to set up a remote target cam that broadcasts a video picture to a screen at your shooting station.

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August 9th, 2016

New Zeiss Conquest Gavia 85 Spotting Scope Looks Good

Zeiss 85mm spotting scope HD glass Gavia Conquest

Carl Zeiss Sports Optics has introduced a new 85mm spotting scope, the Conquest Gavia 85. This new 30-60X spotter is a modern, shorter and lighter design that may challenge Kowa’s category-leading 88mm Prominar spotter, at a more attractive price. The Zeiss Gavia 85’s MSRP is $1999.99. You can pay $2100.00+ for the Kowa 88mm Prominar angled BODY ONLY. Kowa’s 25-60X Prominar LER Eyepiece runs another $569.00, so total cost approaches $2700.00 for the Kowa system.

The new Conquest Gavia 85 angled spotting scope combines 60X max magnification with a wide-angle field of view. A large center ring allows fast, positive focusing. Zeiss claims the large 85mm objective and low-dispersion HD glass provides “outstanding optical performance and brightness” plus great low-light performance. For a spotting scope with a large 85mm objective, the Zeiss Gavia 85 is lighter than expected. With 30-60X removable eyepiece, this spotter weighs in at 60 ounces (3.75 lbs. or 1.7 kg). The spotter is fogproof and waterproof, with LotuTecĀ® lens coatings for easy cleaning and good clarity in all types of weather.

Zeiss 85mm spotting scope HD glass Gavia Conquest

Zeiss 85mm spotting scope HD glass Gavia ConquestZeiss Conquest Gavia 85 Specifications:
Magnification: 30-60X
Objective Lens Diameter: 85 mm
Exit Pupil Diameter: 2.8-1.4 mm
Focal Length (Objective Lens System): 494 mm
Field of View at 1,000 yards: 99-69 ft
Close Focus: 10.8 ft
Lens Type: HD with LotuTecĀ® /T* coating
Length: 15.6 in
Weight (incl. Eyepiece): 60 oz.
Lens Thread: M 86 x1
Retail Price: $1,999.99

For more information on the Zeiss Gavia 85 spotting scope and other Zeiss products, visit www.Zeiss.com or the Zeiss Facebook Page.

Optics Product Tip from EdLongrange. We welcome reader submissions.
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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.”

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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

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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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