PIXFRA SIRIUS S635 AND ARC A419 LRF THERMAL MONOCULARS – Getting Sirius!

Pixfra is the more affordable brand from Thomas Jacks, and although it inevitably plays second fiddle to its blue-chip Pulsar stablemate, it continues to improve. One of the things I like most about the Pixfra range is how rational and easy it is to understand.

Everything on offer

Let’s consider monoculars. There are three series: the ultra-compact Mile 2, the palm-sized Arc, and the new full-sized Sirius, meaning you can pick whichever form factor best suits your needs. Across these series, you can choose between entry-level (256x192), mid-range (384x288), or top-end (640x512) sensors. Between mid-range and top-end sensors, the former will give you around 50% more magnification, whereas the latter will increase your field of view by around 65%, and the price difference is around 20%. Next, decide which lens size suits you best. Each series offers several lens options, ranging from 10mm to 25mm in the Mile 2 series, 19mm to 50mm in the Arc series, and 25mm to 50mm in the new Sirius series. Increasing the lens size reduces the field of view but increases image detail and thus the unit’s “detection distance”. Finally, the price increments from one model to the next within each series also make good sense, so you can easily find a match between your needs and your budget.

Better still, whichever sensor and lens you opt for, the remaining feature set for each series is constant, so you can count on getting the same display, functions, storage, connectivity, and accessories, whichever model you choose. Thus, all models in the Sirius series feature a pin-sharp 1920x1080, 0.49” OLED display; all those in the Arc series are equipped with a smaller but still very capable 1440x1080, 0.41” equivalent; and the minimalist Mile 2 series gets an 800x600, 0.32” OLED across the board. Likewise, all models offer recording with audio, but storage size is 16GB, 32GB, and 64GB for the Mile 2, Arc, and Sirius series, respectively.

The Arc

Thomas Jacks kindly sent examples from the latest Sirius and Arc LRF series for this review. We’ll begin with the Arc.

LRF versions of the Arc series are new for 2025. As an upgrade, they are attractively priced, especially if you opt for the LRF A435 model, which costs just £30 more than the standard A435 (though, for some reason, the LRF A419 is £50 more, and the LRF A635, £80 more, than their standard equivalents). Even for £80 extra, however, that’s excellent value for an integrated rangefinder with a range of 1,000m. Also very much to like is how neatly Pixfra has incorporated it into the Arc’s compact magnesium-alloy housing, tucking it under the objective lens in a way that is both aesthetically pleasing and ergonomically unobtrusive. A quick press on the farthest of the three control buttons on top of the unit activates an aiming reticle (in Pixfra’s signature lime green), and a second press displays the resulting range in a small box in the upper right of the screen. The rangefinder can be configured within the menu to give values in yards/meters and to single-shot or continuous mode.

Other features of the Arc are as per the rest of the series: the housing is nicely shaped to fit in your hand, with extra grip coming from an inset rubber panel, while the textured rubber armouring around the objective lens and rear dioptre ring provides positive front-and-rear focus control. Keeping hold of the unit is further facilitated by a Palmcorder-style hand strap and an optional neck strap. Finally, a rubber, rotatable eyecup, equipped with a flange that eliminates back-reflection and light leakage, aligns your eye comfortably with the display.

Power comes from a single, rechargeable 18650 (3,200mAh) battery that installs easily in a neat compartment under the eyepiece. Both the Arc and the Sirius are supplied with two of these batteries and a smart dual-station charger with a digital display. Each battery provides a nominal 7.5 hours of run-time to the Arc, and 6 hours to the Sirius, whose larger sensor and display draw more power, so having a spare charged cell in your pocket gives you a massive operating window. Both units also have a USB-C port that allows on-board charging and data transfer, though the latter is mostly done using the on-board Wi-Fi in conjunction with Pixfra’s smartphone app, available in Android and iOS versions. A neat feature of the app is that it permits live viewing of the thermal image for up to four people simultaneously, a scenario in which the Arc and Sirius’ built-in tripod sockets also come in handy.

Moving on to the Arc’s controls, these are mounted in a single row on top of the unit and are easily identified by touch and manipulated by either hand. The power button is distinguished by its lime-green colour, and a low ridge separates it from the remaining three buttons, comprising a square central Menu button flanked by round Laser and Zoom buttons.

Imaging is via a long press on the Laser button (video) or a simultaneous press on the Laser and Menu buttons (stills). The Zoom button scrolls through 1x/2x/4x/8x (short press) or calibrates (NUCs) the sensor (long press), while on the Menu button, a short press scrolls through the six colour palettes (white-hot, alarm, black-hot, green-hot, iron-red, and sepia), and a long press accesses the menu, where any manual tuning of the image is carried out. You can fiddle with these settings, but Pixfra’s image processing is AI-controlled. Pixfra claims it “learns from every image captured on the Sirius, ensuring every image looks great, regardless of conditions”, and I can confirm that it works very well.

The Sirius

The control layout is different on the Sirius, for two reasons: firstly, there’s no LRF, and secondly, its power button is neatly integrated into the Pixfra logo on the left-hand side of the housing, leaving just three buttons along the top to navigate: image capture (long press for video / short press for stills), Menu (long press for menu access / short press for palette scrolling), and Zoom (long press for NUC / short press for zoom scrolling). There’s less tactile differentiation in the buttons this time, but the sheer simplicity of the layout more than compensates.

The Sirius is obviously a bigger unit than the Arc (194.3x54x65.4mm vs. 168x50mm, and 421g vs. 360g), but it is still comfortable and secure in the hand. In place of a palm strap, you get both a wrist strap and a neck lanyard, as well as a very practical soft carry case. The Arc also comes with a case, but its hard-bodied construction makes it better suited to storage than to field use. Also good is the lens cover, which is metal, reversible and permanently attached – all of which I like.

The Sirius carries its 18650 battery in a compartment set into the left-hand side. On release, the cover detaches entirely from the housing, retained only by a broad tether that also pulls the battery clear of the contacts. This is a genuinely fingernail-friendly solution! The Sirius is stylish, too, with carbon-fibre panels and lime-green accents. In short, nothing about it says “budget”. I remember the very first Pixfra models having a rather flimsy feel, but the current crop has real visual and tactile presence. My only gripe would be that the buttons are sometimes too sensitive, causing the unit to come out of standby or to switch palettes as they make contact with their surroundings.

Out and about

The loan period on both units was generous enough for me to get out with them for several stalking sorties, a couple of foxing sessions, and one go at the rats. Imaging was obviously better with the Sirius, due to its larger screen and wider field of view (which I always prefer over magnification in a spotter), but both made easy work of detecting and situating animals in the landscape, and I experienced no difficulty identifying what I was observing with either unit. As mentioned, the menu gives you a good deal of control over the image parameters, but the more I used both units, the happier I was to leave that to the onboard AI.

Interestingly, and despite my preference for the image from the Sirius S635, over the course of my testing, I started to gravitate towards taking the Arc LRF A419 by virtue of its laser rangefinder. The Sirius does have a stadiametric rangefinder function, which is better than nothing, but it is slow and coarse compared to the swift precision of the Arc’s laser. Previously, I’ve scoffed at LRF-equipped spotters, regarding their extra functionality as unworthy of the additional bulk and cost, but the Arc LRF’s slender lines and accessible pricing have definitely changed my mind on that score.

Both the Arc LRF and Sirius series are excellent value for money, with the former priced between £1,049.95 and £1,589.95, and the latter between £1,449.95 and £2,519.95. The top-of-the-range Sirius is extra-special, too, as it features a dual-focal-length (25mm/50mm) lens that delivers two levels of optical magnification on demand, but that, as they say, is a story (or review) for another day!

Contact: Thomas Jacks - www.thomasjacks.co.uk