Pixfra Sirius S650D Thermal Monocular Review: Doubly Sirius

Pixfra is Thomas Jacks’ accessible alternative to the premium Pulsar range, but it’s quickly carving out a distinctive identity of its own. The latest proof of this is the Pixfra Sirius S650D: a full-sized thermal monocular with a high-end sensor, intelligent image processing, and, unusually at this price point, a dual-lens optical system that sets it apart from its rivals.

That dual-lens setup is the S650D’s unique selling point, offering users the best of both worlds when it comes to field-of-view and image detail. It’s a clever solution to a fundamental dilemma, delivering genuine benefits in real-world scenarios. But before diving into what that system does, let’s take a look at the chassis and controls.

What are the Build Quality and Ergonomics?

The Pixfra Sirius S650D is built and presented with appreciable helpings of both care and flair. At 223mm long and weighing 537g, it’s undeniably full-sized and carries some heft. That said, it doesn’t feel cumbersome. The balance is good, the grip is secure, and the contours of the housing fit comfortably in the hand. So, whilst it’s arguably a bit of a chunky boy, it never feels overbuilt or clumsy.

The external finish reinforces the excellent first impression. Carbon-fibre-style panels on the body sides, along with lime-green accents that are at once striking and discreet, signal that this is no mere tool, but rather a device whose designers took pride in, with attention paid to form as well as function. Conversely, while the embossed treads on the focus and zoom rings give excellent grip, those on the former are styled after the “X” in Pixfra’s logo. The overall effect is a design that’s grounded in practical intent, but lifted by a quietly distinctive signature.

The hinged metal lens cap is another well-thought-out detail that’s reversible, rugged, and always to hand. The included wrist strap, neck lanyard, and above all, the soft, quick-access carry case, are equally welcome additions. Many thermals come with rigid cases better suited to storage than field use. The S650D’s case is a rare and very welcome exception.

How are the Controls and Features Laid Out?

Pixfra has wisely opted for simplicity here. On the top of the unit, you’ll find just three buttons: capture, menu/palette scroll, and zoom/NUC. Each has a single-click and long-press function, and all are generously spaced for reliable one-handed use, even with gloves on. The operation was therefore accurate and intuitive.

The outlier is the power button, which is integrated into the Pixfra logo on the left-hand side. Sitting just below flush, it can’t be accidentally activated, but it is harder to locate by feel, which is less than ideal when trying to react quickly. It’s also the only control that isn’t ambidextrous. Repeated use when toggling standby mode taught me to find it fast, but it still feels like a rare instance of form getting the better of function.

The Sirius runs off a single 18650 battery installed behind a panel on the left-hand side. Flicking the small but tactile release catch releases the panel, revealing a broad tether that sits behind the battery and thus serves to pull it clear of the contacts. This is a genuinely fingernail-friendly solution! Runtime is up to six hours, depending on temperature, which is about standard for this sensor size and display. Storage is a generous 64GB, meaning you can record video, audio, and stills. Connectivity is via USB-C and WiFi, backed up by a well-featured, stable app. The Sirius is also fully IP67-rated for dust and water resistance.

What is the Imaging Performance and Display Quality?

Central to thermal performance are the sensor and the screen. The S650D is equipped with a big 640x512, 12μm thermal sensor with a system sensitivity rating (NETD) of <18mK. In plain terms, this means it can detect minute temperature differences, even in poor thermal contrast situations like damp mornings or misty hedgelines. The sensor feeds into a 0.49” OLED display with a full-HD resolution of 1920x1080px. The top-notch screen is sharp, bright, and large enough to minimise fatigue over extended periods.

Image processing is handled by Pixfra’s PIPS 2.0 system, which uses AI to optimise calibration. This means the unit constantly fine-tunes brightness, contrast, and gain in real time based on observed conditions. As you scan your environment, PIPS 2.0 adjusts automatically, and the more you scan, the more accurate the optimisation becomes. It sounds too good to be true, but it really works.

The palette selection includes the usual six colour modes. It is a bit too easy to switch palettes accidentally, however, so I’m hoping future firmware will introduce customisable menus that permit deactivating options you never use and don’t want to scroll through.

How Does the Dual-Lens System Work?

The fundamental dilemma when choosing a thermal monocular is: “Do I go for a wide field-of-view for detection and location, or higher magnification for identification and observation?”. The S650D is the first spotter simply to answer “Yes”. It is genuinely the best of both worlds, with two monoculars in one unit.

A simple twist of the zoom ring switches the objective lens between a wide-angle 25mm f0.88 and a much tighter 50mm f1.1, and between two native optical magnifications (1.72x and 3.45x) without resorting to digital zoom and the image degradation that typically brings. However, PIPS 2.0 is also remarkably good at rebuilding a smooth image as you zoom in on the screen using the four-stage digital zoom.

There are a couple of points to note. First, the transition between the two lenses isn’t parfocal; a quick refocus is needed if you stop midway. Second, the juxtaposed zoom and focus rings have different “treads” but remain overly similar in feel, making it easy to grab the wrong one.

How Does the Sirius S650D Perform in the Field?

I liked both the soft carry pouch with its silent, one-handed opening and the monocular’s streamlined, snag-free form factor. Grip, balance, and control were all good. The minimalist control layout proved intuitive, and any early mistakes with the zoom and focus rings were soon forgotten as familiarity grew.

I loved the dual-focus functionality, too. The S650D’s 25mm setting gave me a great wide-angle baseline for scanning, and an almost instant switch to 50mm for detailed ID and observation, with none of the visual compromises of digital zoom. The AI-driven image adjustment was also impressive. The unit never missed a beat. It simply adapted, which is just what you want when time matters.

The Verdict: Is the Pixfra Sirius S650D a Good Value?

The Pixfra Sirius S650D offers serious flexibility in a tidy, well-constructed package. It combines robust build quality, clear design logic, and excellent imaging performance with a dual-lens system that genuinely extends what a single thermal monocular can do.

There are compromises: the power button placement and the tactile similarity of the adjustment rings both provoked initial fumbles. But what really matters is how the device performs where it counts: in the field, in the dark, and under pressure. Most importantly, the Sirius S650D means you no longer have to sacrifice field-of-view for magnification, or magnification for field-of-view, as you get both, in one perfectly integrated package, at an invitingly affordable MSRP of £2,519.95. For versatility and value in a thermal spotter, that’s an unbeatable combination.

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