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View Poll Results: Does the kobo forma light flicker cause you eye strain?
yes 1 3.13%
no 31 96.88%
Voters: 32. You may not vote on this poll

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Old 10-31-2018, 02:24 PM   #1
Jason90
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Kobo forma screen flickering/pwm issues

Well i have some very bad news for people who wish to purchase the forma and are sensitive to screen flicker/pwm (pulse width modulation)

Got my device today, however after coming across this video i decided to do the same and also noticed my forma flickering.

Here's my kobo: https://youtu.be/B8Oc3FcizyY

It does this on all brightness levels except with brightness and natural light both at 100%,i.e when all the leds are on.

This is PWM (Pulse width modulation) which is the worst culprit of eye fatigue and headaches ,totally beats the point of an ereader!

Kobo have really screwed up here as the design of the device itself is the best of any ereader i have purchased in the past and i'm quite saddened by this!

A part of me really wants to keep it but as i do alot of reading at night i can't keep the device at 100% brightness so it's going back i'm afriad.

I've added a poll to let other owners report this issue and if it bothers them or not.

Last edited by Jason90; 10-31-2018 at 02:28 PM.
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Old 10-31-2018, 02:37 PM   #2
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Well basically you get eye relief from the comfort light, and then some strain from the PWM. So its great, compensated :P .
Joking aside, its 2018 and even many of monitor manufacturers are going for CV(constant voltage) instead of pwm on the light. Having PWM in an e-reader, and on a premium model on top of that, is a big turn off and the last nail in the coffin.Was considering the forma, but if this isnt changed in later revision, then they can keep it for themselves.
Way to save few cents on a 280$ reader KOBO, *slow clap*
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Old 10-31-2018, 02:49 PM   #3
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I've read several hours on the Forma with no eye strain/head aches, etc.
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Old 10-31-2018, 03:05 PM   #4
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Hmm, I do not use backlight, however back in the day when most LCD still widely employed PWM, there were lots of thoughts on the subject. IIRC flickering will cause headaches/fatigue if the cycling frequency is low enough (however low depends on each person), and a very high cycling frequency shouldn't cause any fatigues to the human eyes. Now the only way to know the frequency is using expensive oscilloscope, which I doubt any ereader reviewer would have in their possessions.

I'm willing to test using the forma for a week using backlight; however, I fear I might be prone to placebo/bias i.e. I know it employs PWM so my brain will trick me into thinking that the backlight causes me fatigue .

Would be interesting in hearing some replies from Kobo on this design choice. One thing I do notice is the 1% brightness of the Forma is much lower than the previous readers, and you also got more fine control in low brightness level (e.g. from 1->11).
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Old 10-31-2018, 03:07 PM   #5
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I can test this on my Forma if needed (filming it, etc...) but as far as I know it's not an issue for me whatsoever.
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Old 10-31-2018, 07:53 PM   #6
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Nope and I’ve read for hours on it in all sorts of light conditions.

The guy in the first video loses points because he asserts that this will cause eye strain and headaches for everyone even if they don’t think it will after saying he wasn’t sure about just that same issue.

If it affects you sorry. But don’t assume it’s going to bother everyone.


ETA lol I just tested this on my Forma. Brightness at 34 natural light around 50. Used my iPhone XS Max to film it in slo-mo. No flickering.

Tried again at 50% brightness and natural light off, no flicker.

Tried under different lighting again at 50 with natural off, the light from the LED bulb reflected on the screen and that flickered but the rest of the screen was fine. The first test was done in the same room but with a different angle so the light was bounced off a wall/not direct.

Tried yet another area (bathroom) with multiple lightbulbs above a mirrored cabinet. Finally got a flicker but this was obviously the lights not the screen. Unless my bathroom sink counter uses PWM too and I’m unaware.

In as near as I can get to total darkness save for the iPhone screen and the Forma screen and some very low ambient room light from windows (you would not be able to read in this level of lighting) there was no flicker.

So I dunno if I’m doing this wrong I’m just filming the Forma screen using slo-mo default settings (not even sure you can change these). All tests were done at least on 30 and 50 brightness I didn’t use natural lighting unless otherwise noted.

So do I have a magic Forma or am I doing something wrong?

I saw the flicker in the linked videos so it’s not that I can’t see it.

Last edited by MGlitch; 10-31-2018 at 08:26 PM.
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Old 10-31-2018, 08:36 PM   #7
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I can't see any flicker at any brightness level or at any amber-colour level. If it's there it's invisible to me. I always try not to let phenomena which are invisible, odourless, silent and tasteless spoil my gadget enjoyment
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Old 10-31-2018, 08:47 PM   #8
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Originally Posted by jackie_w View Post
I can't see any flicker at any brightness level or at any amber-colour level. If it's there it's invisible to me. I always try not to let phenomena which are invisible, odourless, silent and tasteless spoil my gadget enjoyment
You should invest in a carbon monoxide detector but otherwise I agree. I can’t see this with my naked eye, I can’t see it in a video I create filming at 240 FPS in various conditions

This is the kind of problem I like to have. One that doesn’t exist.
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Old 10-31-2018, 09:03 PM   #9
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You should invest in a carbon monoxide detector
Yes, we've got a couple of those. My husband's doing, though. Left to me we might both be goners.
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Old 10-31-2018, 09:19 PM   #10
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Btw I’m not answering this poll as it implies that there is flickering and it either bothers you or it doesn’t. As noted I can not replicate this issue and thus I can’t in good faith imply it exists.
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Old 11-01-2018, 07:32 AM   #11
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No flicker with my forma and I'm quite susceptible to those.
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Old 11-01-2018, 09:50 AM   #12
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I don't feel any flickering, and I read hours together, while my eyes hurt if I remain that long in front of my PC. Could the flickering filmed in some of those videos be due to the ambient light?
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Old 11-01-2018, 11:02 AM   #13
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My Forma doesn't have the problem either. I'm wondering if Kobo has two OEMs for the lights or if they just had a bad batch.
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Old 11-01-2018, 03:35 PM   #14
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My Forma doesn't have the problem either. I'm wondering if Kobo has two OEMs for the lights or if they just had a bad batch.
Or if the OP thinks one experiment is enough for a data set.
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Old 11-01-2018, 05:17 PM   #15
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I can’t see this flicker either
But I also dont have this line down the side, so maybe there are different batches
The only thing that really bothers me, it seems (at full night mode) much less red than the Aura One. I like the Aura One much better in this respect
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