Boox Note Air5 C Review: Colour E-Ink, Carefully Refined

The Boox Note Air5 C is the third iteration of a well-established family, and it makes no attempt to surprise. It picks up where the Note Air4 C left off, keeping the same chassis as that model — a chassis already carried over from the Note Air3 C. Anyone hoping for a change of look will not find it here, which leaves one straightforward question: are the adjustments enough to justify the upgrade?

On paper the specification sheet delivers what a high-end note-taking slate and e-reader should. There is a 10.3in Kaleido 3 colour e-ink panel built on Carta 1200 technology, a Qualcomm Snapdragon 750G octa-core processor clocked at 2 GHz, 6 GB of RAM and 64 GB of storage that can be expanded with a microSD card. The whole thing runs Android 15, where the Note Air4 C stopped at Android 13.

Side by side, the Note Air5 C is hard to tell apart from its predecessor. Boox has introduced only two physical changes over the previous generation. The first is a set of POGO pins on the back of the device, intended to connect the optional keyboard. The second is a pair of small physical buttons on the right-hand edge, assigned to page turning, volume control and other functions the owner can customise.

The format stays A5, with dimensions of 225 x 192 x 5.8 mm. Weight climbs to 440 g without the case or stylus. That is more than the 420 g of the Note Air4 C, and clearly more than the 375 g of the Boox Go 10.3. Nothing dramatic in day-to-day use, but a generational update that adds weight does run against expectations.

Ergonomically there is plenty to like. The power button, on the top edge near the upper-left corner of the screen, doubles as a fingerprint reader. The USB-C port on the left edge handles charging and data transfer and remains OTG compatible. The slight asymmetry of the front face is particularly welcome, because the small border lets the palm rest without accidentally interfering with the screen.

A pair of speakers and a microphone are built in. There is no camera, front or rear, and no waterproofing rating. On a note-taking slate the missing camera may seem justified, although anyone in the habit of dropping photographs into their notes will be disappointed.

This is the heart of the matter on a device of this type. The 10.3in Kaleido 3 panel displays up to 4,096 colours. In monochrome it reaches a resolution of 1860 x 2480 pixels, or 300 ppi, a comfortable density for reading and writing. Switch to colour and the resolution drops to 930 x 1240 pixels, or 150 ppi. The difference is immediately visible, and it is the price of Kaleido 3, which lays a colour filter over the monochrome e-ink layer.

Colour on an e-ink panel remains a compromise, and the laboratory measurements recorded during testing bear that out. Maximum brightness came in at just 78 cd/m². That is an improvement on the 66 cd/m² of the Air4 C, but the gain is as modest as it is far from the best e-readers, with the Boox Go 7 measured at 171 cd/m².

In practice this causes few problems indoors or outdoors, because reflectance has fallen again, to 31.9% against 37.2% previously. That is progress, though it does not make the panel immune to glare: outdoors, a strong light source pointed directly at the screen still needs avoiding.

Then comes colour accuracy, the perennial sore point on colour e-readers. The good news is that average Delta E has edged down to 16.2, from 19 on the previous model. It is still far too high. Delta E measures how far colours stray from a reference, and lower is better; the best smartphone and tablet screens sit at 1. There is a long road ahead for colour e-reader panels, because the limitation lies with Kaleido 3 itself.

Even with such a high figure, the panel remains a long way from genuinely faithful tones. It recovers some ground with a measured colour temperature of 6562 K, a hair away from the ideal, although that figure essentially describes the white point. Contrast is a slight disappointment: after the 15:1 of the previous generation, this one falls back to 13:1. Everything stays perfectly legible, but it lacks bite.

For annotating a colour PDF, highlighting or reading a graphic novel, it is sufficient. For anyone expecting something close to a conventional tablet, calling it a distant prospect would be generous.

To offset the native slowness of e-ink, Boox includes its own BSR (Boox Super Refresh) technology, which leans on a dedicated GPU to improve refresh rates. Scrolling is genuinely smoother than an electronic-ink panel would normally manage.

The move to Android 15 is one of the real changes this generation. In practical terms it mainly buys longevity, since this version of Android will not become obsolete quickly, and it improves compatibility with recent apps. Boox also highlights split-screen, OCR and cloud synchronisation, all of which benefit from a more modern Android base.

The Boox ecosystem on Android 15 opens up the Play Store and a wide range of applications, which is the device's single biggest advantage over more closed rivals. A large part of its value lies there, because it stretches well beyond note taking towards a genuine tablet, within the limits electronic ink imposes.

Among e-readers, Android models are by far the best for file-format support. Thanks to Play Store apps they can read essentially anything, audio formats included. The reading experience is very satisfying on a slate this size, for books as much as for graphic novels, comics and manga, although its dimensions make it less manageable than a compact e-reader.

Boox still lays its own interface over Android. It is plainer and graphically more simplistic, but it retains home screens on which apps, folders and widgets can be placed.

The Snapdragon 750G is no powerhouse, and that is deliberate: it does the job expected of an e-ink slate while drawing less power than more capable parts. Backed by 6 GB of RAM, it handles the Android 15 interface without any major stumble.

Display fluidity can be tuned fairly precisely, but the smoother the experience, the greater the cost to battery life. The 64 GB of storage may look tight, though the microSD slot allows it to be extended as needed. Connectivity covers Wi-Fi and Bluetooth 5.1 — nothing extravagant, but the essentials are there. Because this is Android, a fully capable web browser such as Chrome, Brave or Firefox is also an option.

The Note Air5 C ships with the new Boox Pen3, a Wacom EMR-compatible stylus that works without a battery. It claims 4,096 pressure levels, tilt sensitivity and very low latency, which suits sustained handwriting, and the battery-free design never needs recharging.

Where the writing feel was unconvincing on the Air4 C, it now comes across as more credible and better resolved. It is not yet at the level of reMarkable products, but the progress is worth noting. The one persistent irritation is that the tip cannot double as an eraser. Replacement nibs are hidden in one end of the stylus.

The native note-taking app is similarly serious, handling up to five layers. Since the template forms the base layer, six can effectively be stacked, which is enough to structure detailed notes or multi-level sketches.

Battery life is difficult to pin down on a device of this nature, because testing it like a conventional Android tablet would make little sense — and few people would buy something like this to use purely as an e-reader.

Under mixed use consisting of long reading sessions, a little for books and a great deal for graphic novels and comics, followed by morning web browsing, with brightness set to halfway and total use capped at around an hour and a half to two hours a day, the 3,700 mAh battery lasted roughly four days between charges.

Under heavier use closer to that of a conventional tablet, that falls to about ten hours. At the other extreme, a reading-focused workload can reach around 24 hours of continuous use. Battery life on an e-ink slate depends enormously on what is asked of it, and the Note Air5 C is no exception. The Snapdragon and Android 15 both tend to push consumption above that of a simple e-reader.