August 13, 2020
By Tom Beckstrand
The hunting scope market just got a little more competitive with the introduction of the Vortex 3-15x42mm Razor HD LHT. Hunting scopes are the largest segment of the rifle scope market and Vortex has only offered a few specific options in the past. The Razor HD LHT is the expansion of the brand’s premium hunting line and consumers looking for good low-light transmission, light weight and optical clarity, will find that the Razor HD LHT has all these in spades.
“Small” objective lens?
The Votex’s 3-15X magnification range coupled with the 42mm objective lens is an ideal combination for a hunting optic. If I had to make a prediction, I’d say this is where the photographers are going to show up and ask, “Why doesn’t it have a bigger objective lens to let in more light?” Rifle scopes don’t work like camera lenses and there is a lot more to a bright visible image than the size of the objective lens.
The larger the objective lens, the larger the exit pupil. (That’s the size of the “hole” in the back of the scope that you look through.) In an ideal situation, the exit pupil matches the size of the shooter’s own pupil, ensuring maximum light transfer to the shooter’s eye. To calculate the exit pupil, divide the objective lens by the magnification. At the maximum power of 15X, the Razor HD LHT has an exit pupil of 2.8mm. (“HD” stands for “High Definition,” and “LHT” is “Light Hunter Tactical.”)
The pupil in the human eye can dilate to as high as 5mm in near darkness, according to a U.S. Special Operations Command study. This is where advocates of bigger objective lenses step in and say, “Gee, I wish it had a 50mm objective lens on there.” I’m not one of those guys. Bigger objective lenses are heavier. Not only is the optic heavier, the scope is more likely to have a point of impact shift if the optic is jarred or dropped.
It also costs more money to get similar image quality off of a larger lens than a smaller one. Making the lens bigger to make the image brighter does no good if all the manufacturer achieves is a bright blurry image. The larger lens has more surface to shape, which takes time and money, so cost for the bigger objective lens goes up to achieve the same degree of resolution as the smaller lens.
Finally, if the exit pupil needs to be bigger to get that brighter image, dial down the magnification. Instead of putting the heavier and more expensive 50mm objective lens on this scope, the shooter should dial down magnification to 12.5X. Fifty divided by 15 equals 3.33mm. Forty-two divided by 12.6 also equals 3.33mm. Moving from 15X to 12.6X on this scope makes the image as bright as using a bigger 50mm objective lens, and no one is going to miss the 2.4X given up to get it.
Resolution & Contrast
Vortex knows all of this and that’s why there’s a 42mm objective lens on this model scope. Vortex knew that the Razor HD LHT needed excellent light transmission, maximum resolution and great contrast. Resolution and contrast are a couple of the aspects of scope performance that are hard to quantify, especially from the layman’s perspective. As a result, they don’t get much coverage when they should be getting the most coverage.
Years ago as a sniper student at the USMC Scout-Sniper Advanced Course, I did sniper-versus-sniper stalks to see who could spot the other guy first. The two main reasons for the guys getting spotted were that their camouflage was either the wrong color or the wrong texture. (Each student made heavy use of vegetation, so that was the primary camouflage.)
Color detection and contrast with a riflescope is a function of the coatings used on the glass. The coatings on the LHT are excellent, giving this scope excellent contrast. Colors “pop” and it’s easy to distinguish one color from another. Detecting texture is a function of resolution. In the scenario described above, snipers were spotted because they had big leaves attached to their ghillie suits instead of small leaves. Spotting this type of discrepancy requires good resolution to clearly see the size of the leaves.
Resolution and contrast also play an important part in spotting hidden game. Animals wandering around the countryside in broad daylight aren’t hard to spot, but that rarely happens. Animals usually hide in shadows and it takes really good resolution and contrast to spot a dark animal against a darker background. Cheap optics turn shadows muddy and make it impossible to see the outline of the tell-tale ear or antler.
I spoke with a source inside Vortex about the Razor LHT and he said the module transfer function (MTF) numbers on all the Razor LHT scopes he’s tested are almost identical. They’re the best numbers he’s seen on any scope, not just the scopes Vortex makes. (MTF is a test run to measure optical resolution and contrast. Unlike the U.S. Air Force’s chart from the 1950’s that’s frequently used for resolution and contrast testing, MTF is a computerized test most frequently run on camera equipment.)
What Vortex has found is that the new Razor LHT has contrast and resolution numbers that match scopes costing four times as much. Those exceptionally high resolution and contrast numbers are limited to the center of the field of view because it takes a lot of time and money to carry perfection all the way to the edge of the lens.
While there is some fall-off in image quality as the eye moves to the lens’ edge, it isn’t much. Personally, if I’m looking hard at something, I’ll be using the center of the field of view. Getting the same performance out of the LHT as something costing four times as much represents a whole lot of savings for a small trade-off in performance.
While the optics inside the Razor LHT are excellent, the mechanics saw the same amount of effort. Vortex designed a new zero-stop system that is functional and economical. Once in place, this new zero-stop allows for two full revolutions of the turret.
Many scopes retailing for less than $1,500 will probably have a zero-stop that will need to be installed by the user. Elevation turrets with integral zero-stops are complex and costly. User-installed zero-stops save a lot of money. However, the problem until now has been that user-installed zero-stops only allowed for one turret revolution. If the elevation turret only has 5 mils per revolution, that only equates to about 800 yards of travel for my pet 6.5 Creedmoor. A rifle in .308 Winchester would be significantly less.
The Razor LHT has 6 mils per turret revolution (22 mils overall) and the user-installed zero-stop allows for two turns of the turret. This means I can dial 12 mils of travel and that would take my same 6.5 Creedmoor out to 1,350 yards. That’s well beyond anything I’d need from this scope.
Installing the zero-stop takes less than 2 minutes, if you take your time. Once the scope is zeroed, loosen and remove the screw in the center of the turret cap. Lift the turret cap off, place the zero-stop around the center post (pin down), rotate the zero-stop clockwise until it stops, replace the turret cap and center the screw. It’s caveman-simple, economical and effective. Once in place, the turret can dial .5-mil under the zero and two full revolutions above it.
I wanted to see how well this new scope was made. I don’t have an MTF machine at the house, so I figured testing for reticle cant and accurate tracking would have to do. My tracking test involved shooting rounds across 14 mils of erector travel and then measuring the distance between the two furthest groups.
Since tracking errors are a percentage, doing a tracking test of only 5 mils, or so, would only expose gross error. I measured 0.7 percent tracking error across 14 mils of travel. This was exceptional and was likely that the small amount of error was within the noise of what I could measure. I checked for reticle cant across the same 14-mil range and could measure none. While this is a new scope for Vortex, to date, these are some of the best results I’ve recorded for any optic.
The Razor LHT will appeal to anyone interested in a high-quality hunting scope that also offers great value. It has excellent optics, easily competing with more expensive scopes, and some of the most accurate mechanics I’ve recorded. These features and this reticle are appropriate for what most hunters are looking for in today’s market.
Vortex Razor HD LHT
- Power: 3X-15X
- Objective: 42mm (tested), 50mm
- Tube Diameter: 30mm
- Elevation Adjustment: .1 mil per click
- Windage: .1 mil per click
- Reticle: HSR-5i (MOA)
- Length: 13.3 in.
- Weight: 19 oz.
- Eye Relief: 3.8 in.
- MSRP: $1,400 (tested)
- Manufacturer: Vortex, 800-426-0048, vortexoptics.com
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