June 25 2021
Product: Vortex Diamondback HD 8 x 28
Country of Manufacture: China
Field of View: 101m@1000m(6.2 angular degrees)
Eye relief: 18mm (advertised), but a lot less in practice.
IPD Range: 55-72mm
Close focus: 1.83m advertised 1.75m measured
Chassis Material: Rubber Armoured Magnesium alloy
Coatings: Fully multi-coated, dielectric coatings on prisms, phase correction coating, Armotek hydrophobic coatings on outer lenses.
Dioptre range: +/- 4 dioptres
Gas purging: Yes Argon
Waterproof: Yes (unspecified depth and time)
ED Glass: Unknown
Dimensions: W/H 11.7/11.4cm
Warranty: VIP Unlimited Lifetime
Supplied With: padded carry case & strap, lens cloth, instruction manual, logoed padded binocular strap, rubberised ocular and objective tethers
Retail Price: £135 UK/$170US
Vortex Optics is a US-based company specialising in sports optics for the hunting, birding and the outdoor enthusiast. They have brought to market an extensive range of binoculars from entry-level right up to low-end premium, manufactured in China or Japan. Arguably their best-selling series is the Diamondback range of roof prism binoculars. Over the last 15 years or so, Vortex has upgraded and modified the design of these binoculars, where they are widely considered to offer the best performance to cost ratio on the market. This review will be looking at the newest, third-generation of the Diamondback – the so-called Diamondback HD series, which first hit the market in 2019.
I purchased the Diamondback HD 8 x 28 with my own money and the opinions I offer are entirely unbiased, unlike a lot of fake reviews of said products all over the internet.
The instrument arrived in a single box, containing the binoculars wrapped inside a plastic bag and securely placed inside a black padded case. I received a neck strap, lens cleaning cloth, rubber ocular and objective tethers, and a strap for attaching to the carry case. The full-colour instruction manual offers all the basic information you need to adjust the binocular to get the best use out of it.
As I removed the binocular from its case and assessed its fit and feel, I was quite impressed. This was a solidly made binocular with a tough army green rubber armouring, ribbed at the sides for a more solid grip. The little Diamondback has good quality metal-over-soft rubber twist-up eyecups and a large, silky smooth central focus wheel. The dioptre ring located under the right ocular is a bit hard to access, as it’s very resistant to movement; a good thing I suppose as one normally doesn’t want this to move easily while out in the field. Only by twisting up the eyepieces could I negotiate moving it to my preferred dioptre setting.
The objectives are quite deeply recessed for a small binocular(4mm) which helps protect the lenses from dust, rain and peripheral light. Inspecting the inside of the instrument showed that everything was clean and dust free. The ant-reflection coatings applied to both the objective and ocular lenses appear to be very smoothly applied and give a faint greenish purple tint in broad daylight.
The twist-up eyecups have three settings and once they click into place, hold their positions rigidly. The focus wheel is covered in a textured rubber which makes gripping and rotating it very easy. Moving from close focus – measured at 1.75m – to infinity involves two full rotations of the wheel, and I was pleased to see that there was very little play or backlash throughout its motion, either clockwise or anti-clockwise.
Ergonomically, the Diamondback HD 8 x 28 feels solid in the hand and is small and light enough to carry along on extended trips.
The Diamondback HD is weatherproof, O-ring sealed and purged with dry argon gas. In most other binoculars built for the great outdoors, dry nitrogen is used to replace the air inside. I suppose argon, having a larger relative atomic mass than molecular nitrogen, might diffuse out more slowly than the latter, but whether this has any real advantages in practice is debatable.
With the advertised full-featured coatings used in the manufacture of this binocular, I was expecting a good result from my smartphone flash light test. Directing an intense beam of light into the binocular and looking through the eyepieces, I was pleased to see a very clean image, with very well suppressed internal reflections and with little in the way of diffraction spikes evident. Neither was there any diffused light showing that the glass was very homogenous and free of major artefacts. This would be a good performer looking at artificial lights at night or casual moongazing, as my subsequent tests indeed confirmed.
But while I was using it in the field, I uncovered a significant issue with the Diamondback HD 8 x 28. When I fully extended the eye cups and locked them into place, I was very surprised to experience pretty severe blackouts and it was very challenging to see the field stops. Indeed, instead of normal well-defined edges to the field, I was seeing a ‘ring of fire’ around the edges which I found quite distracting. I quickly realised that the eye relief was just too short for me to obtain a stable binocular image with no blackouts. I had seen this before but in a far less extreme way while using a Leica Trinovid HD 8 x 32 binocular, which has multiple twist-up positions. If I had inadvertently not pulled these eye cups fully out, I got more blackouts and these would alert me to the problem. So the same issue must have been happening in the Diamondback HD binocular, only it was much more severe.. Only by pulling my eyes away from the eyecups could I obtain a reasonably stable field but I have to admit that I found this to be quite annoying.
More’s the pity as otherwise the Diamondback HD 8 x 28 served up a very bright, high-contrast image rich in detail and with a large sweet spot. Depth of focus in this instrument is good too. Colours were very vivid and realistic and it even exhibited well-above-average control of glare. Edge sharpness was also very good with only slight colour fringing seen on high contrast objects beginning about 70 per cent out from the centre. I have no idea what the term ‘HD’ means – ‘High Density’ perhaps, or ‘High Definition’ even? And if HD indicated the use of some low dispersion objective element, why not just call it ED in line with most other models? All I can say is that the image was of impressively high quality but somewhat off putting by the positioning of the eyecups.
When I tested the unit under a clear twilit June sky at night, star fields were impressively presented with bright luminaries like Vega, Arcturus and Deneb focusing down to sharp pinpoints and remaining tightly focused nearly all the way to the field stops. Again, this result was better than expected but I suspect that it is due to the rather small field served up by this binocular. Simply put, by restricting the field of view, binocular designers can mask more severe distortion and field curvature that would show up in a larger field. Views of a low-hanging, waxing gibbous Moon were also very good! The bright, silvery orb was clean and sharp and showed no secondary spectrum on axis, but did show up some minor lateral colour as the Moon was moved to the edge of the field.
In light of the many positive reviews of larger Diamondback HD binoculars made by experienced glassers, I am reluctant to write-off this series based on my less than favourable experience of this 8 x 28 model. With their modest cost, above-average optical performance and great ergonomics, I can see why these Diamondbacks enjoy a loyal fan base. Those who wear eye glasses, unlike me, will probably fare OK with these binoculars though. As for me, I returned the instrument and received a full refund, so no permanent harm done.
Thanks for reading!
Dr. Neil English has written over 300 articles for various astronomy, religious and birdwatching magazines over the last 25 years, and is the author of seven books on amateur and professional astronomy. His magnum opus, Chronicling the Golden Age of Astronomy, continues to go from strength to strength among serious astronomy historians.