“Does the Kobo Forma Have PWM Flicker Issues Affecting Your Reading Experience?”
The Kobo Forma is one of the most intriguing new releases of this year’s eReader lineup. At first glance, this 8-inch eBook reader may look like a doppelgänger of the Kindle Oasis, but it does offer a few useful (night light) and interesting (flexible Mobius display technology) innovations that its Amazon competitor does not.
Unfortunately, you can’t get the Kobo Forma directly in this country, as Rakuten Kobo, a technology partner of Tolino, has long since stopped selling reading devices in Germany. Interested buyers must, therefore, import this high-end model from the nearest EU country.
However, you might want to reconsider, as reports are circulating that the Kobo Forma’s lighting uses pulse-width modulation (PWM) instead of DC modulation. PWM typically causes invisible light flicker, which nonetheless induces discomfort for some people (see below).
Videos demonstrate possible PWM visibility
On Reddit and Mobileread, there are discussions on this topic, which, although not yet widely trafficked, contain two interesting videos. These show a flickering light made visible through the camera.
One of the videos was recorded in slow motion at 240 frames per second, making the effect clearly visible:
This is noteworthy because, in the past, PWM has often been blamed for headaches and eye strain. Therefore, many monitor manufacturers offer models with DC modulation as a flicker-free alternative. Most eBook readers use flicker-free lighting controls as well.
Why can PWM be problematic?
Of course, it is not automatically said that all Kobo Forma users will have problems due to the PWM control, which is presumably in use. How much one is affected depends on the PWM frequency and individual sensitivities. A detailed description on the topic can be found here.
In short, for brightness control, the light is rapidly turned on and off. The brighter the screen needs to appear, the longer the light phases last. The faster this process occurs, the more invisible it is to most users.
This is problematic because some people react sensitively to such rapid flickering with headaches or eye pain. The reason for this is not entirely understood, but it’s speculated that it might be related to rapid, continuous adjustments of the pupils.
Issue with the Kobo Forma?
The question naturally arises whether the Kobo Forma is generally affected by this. As mentioned earlier, two videos show clear flickering, so it’s safe to assume that at least some devices use PWM for lighting control.
On the other hand, there are voices on both Reddit and Mobileread that report seeing no light flicker despite slow-motion footage. This raises the question of whether there are different versions or if this is due to varying camera settings.
German buyers – aware of their sensitivity to PWM – would be wise to wait for further developments on the topic before importing the device. Should the speculation presented in the videos prove true, it would indeed be unfortunate, especially since E-Ink readers have gained popularity because they’ve largely been free of such issues. In the ALLESebook test a few years ago, the Onyx Boox T68 faced a similar problem.
One can only hope that the Tolino partners will pay attention to such matters when adopting future Kobo models, ensuring that no unchanged eReader model with PWM control will appear in Germany.
