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View Poll Results: Does the kobo forma light flicker cause you eye strain?
yes 9 14.52%
no 53 85.48%
Voters: 62. You may not vote on this poll

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Old 11-01-2018, 05:23 PM   #16
Nimwe
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Quote:
Originally Posted by Stevex View Post
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
If it's not too big of a bother for you, could you please take a good photo of the whole ereader within a dark room and with white (and red in a separate pitcure if possible) ComfortLight on at 100%?
It would help me decide whether to ask for a refund of the forma or for a replacement, I've not asked for a replacement yet because I fear they would just send me another "striped" device
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Old 11-01-2018, 09:15 PM   #17
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Quote:
Originally Posted by Stevex View Post
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
I Originally thought the dark shadow on the right side might be the reason for this flickering but the fact that the flickering/pwm stops when i set the brightness to 100% made me think kobo did this by design.

As people have reported their forma's don't have flickering i'm inclined to go along with a previous members thought that kobo are using different batches of leds for the forma,perhaps one that uses pwm and another that doesn't.

Don't know if a kobo representative ever posts on this fourm but if we could get a definitive answer on this issue if it is something that needs to be fixed or if they are using different led designs.
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Old 11-01-2018, 10:50 PM   #18
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Using my Samsung Note cell phone I took a video of my Kobo Forma screen, and my Kindle Oasis 2 screen. The vertical bars referred to in this post were evident in the video of the Kobo Forma. The Kindle Oasis 2 video has no evident vertical bars. The illumination on both was set at 20 percent for Kindle Oasis 2, and 30-30 (light-natural) for the Kobo Forma.

Having said that, I have yet to notice any obvious eye strain. Nonetheless, pwm would seem to disqualify the Kobo Forma screen as a paper equivalent, at least to sensitive individuals.

I intend a cross-over experiment with two successive days of boring reading (interesting reading results in too many eye-movements and may therefore induce strain independently) with both devices to see whether it matters to me.
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Old 11-02-2018, 11:37 PM   #19
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Quote:
Originally Posted by squiresque View Post
I intend a cross-over experiment with two successive days of boring reading (interesting reading results in too many eye-movements and may therefore induce strain independently) with both devices to see whether it matters to me.
Will be interesting to hear your thoughts after prolonged reading and if you noticed any difference compared to your kindle.

I did state in my OP that users who are sensitive to flicker will be unset about this revelation as i know not everyone seems to be bothered by it.

I'm no eye doctor but it would be interesting to know why pwm affects some but not others,or perhaps it effects everyone but to varying levels.
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Old 11-04-2018, 07:08 PM   #20
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no eye strain after two days of reading from pwm

Just as a followup - I have not noticed any eye strain or headaches from reading the Kobo Forma after two days of reading notwithstanding having demonstrated by phone video that the Forma produces vertical bar pwm pulses not produced by my kindle oasis 2.

I have, however, developed a fresh dislike of the harsh Kindle oasis 2 lighting and much prefer the Kobo Forma lighting --- it's not even close.

Sadly, there remain other Forma problems such as 1) grossly defective orientation sensor, 2) catastrophic device freezes when reading PDFs requiring hard restart, 3) wedge side light defect that disturbs actual text when reading in landscape mode, 4) no contrast adjustment for the bare bones PDF viewer rendering Supreme Court Oral argument transcripts nearly invisible coupled with no as-yet-available support for using third party pdf software, and 5) the apparent official release of a firmware update that fixed some serious bugs, only to break other supported features.

I look forward to being able to become a dedicated Kobo user in the future, and will monitor this forum for improvements.
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Old 11-04-2018, 07:36 PM   #21
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Quote:
Originally Posted by squiresque View Post
4) no contrast adjustment for the bare bones PDF viewer rendering Supreme Court Oral argument transcripts nearly invisible coupled with no as-yet-available support for using third party pdf software,.
I know it's not ideal, but have you tried changing the "ink" colour before putting it on your kobo? I know nothing about such transcripts, and can only guess at the problem, but if it's specific to those PDFs, it would seem like a less than ideal format for reading on a e-ink e-reader. And a little formatting might change that.
However, maybe they are locked documents and no such changes are possible (or legal?).
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Old 11-05-2018, 03:16 PM   #22
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I too have tried replicating the flicker issue and have not been able to detect it. I did, however, notice the shadow on the wedge side of the screen.
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Old 11-05-2018, 03:47 PM   #23
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I did some tests now using the iPhone XS Max camera with following results:

- filming in normal mode -> no flicker
- filming in slo-mo -> flicker for a few seconds, after that no flicker anymore
- filming in slo-mo, portrait -> flicker from left to right
- filming in slo-mo, landscape -> flicker from top to down

if you change the color of the front light and/or the brightness does not affect the flicker speed or amplitude.

As I already wrote, the flicker stops after a few seconds. If you then put a hand in front of the camera while recording and remove it again, it will start to flicker again for a few seconds. After a few seconds, the flicker stops again.

I am not sure if this is PWM or something else that tricks the camera.

I uploaded a video here: https://youtu.be/TTiTNSmnX4k

Last edited by rma; 11-05-2018 at 04:08 PM. Reason: added Youtube video
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Old 11-05-2018, 04:37 PM   #24
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Random potentially extremely stupid idea: could that be the light guide causing moire-like artifacts?
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Old 11-07-2018, 06:22 AM   #25
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Quote:
Originally Posted by rma View Post
I did some tests now using the iPhone XS Max camera with following results:

- filming in normal mode -> no flicker
- filming in slo-mo -> flicker for a few seconds, after that no flicker anymore
- filming in slo-mo, portrait -> flicker from left to right
- filming in slo-mo, landscape -> flicker from top to down

if you change the color of the front light and/or the brightness does not affect the flicker speed or amplitude.

As I already wrote, the flicker stops after a few seconds. If you then put a hand in front of the camera while recording and remove it again, it will start to flicker again for a few seconds. After a few seconds, the flicker stops again.

I am not sure if this is PWM or something else that tricks the camera.

I uploaded a video here: https://youtu.be/TTiTNSmnX4k
Rest assured that it is pwm, your camera just automatically adjusts shutter speed and thats why you stop seeing the flicker after few secs.

I read that few folks mentioned that they dont have issue(headaches or eyes getting tired fast) with pwm.
Basically, pwm constantly turns off and on the light in a given interval, depending on the frequency of the driver they use for the leds.True, there might be no apparent instant harm, but id rather not have such a device shining on my eyes for prolonged intervals of time. Changed my previous monitor just because of that fact.
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Old 11-12-2018, 03:26 PM   #26
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Ok so I'm really interested in the Kobo Forma but the whole PWM thing does worry me a bit. So I've seen some people say it does have PWM (even a few youtube reviewers) but from the poll it looks overwhelmingly that it doesn't matter and it might be at the higher end of the frequencies where it doesn't cause headaches, eyestrain etc.

That assumption would be right…correct?

I’ve asked Kobo a few times but they just keep saying check the specs which says nothing about any of this.

Thanks heaps
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Old 11-12-2018, 03:51 PM   #27
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Some of the youtube reviewers reference or utilize without referencing (which is shameful for them really) mobilereads. So when a post like this pops up they might on it.

I've used my iPhone XS Max on the same settings they claim to be using and got no flicker.

But lets say my device is actually the magic one which somehow escaped this issue. As you note the results of this poll show it's a non-issue for the majority. As does the content of this whole thread.

If you know you're ultra sensitive to PWM maybe don't get the Forma. But if you typically don't get eye strain from PWM then this wont affect you.
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Old 11-14-2018, 11:19 AM   #28
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I've just made a video how it is flickering on my Forma. It is made by Samsung Galaxy Note 8 in slow-motion mode.

Forma is flickering

As you can see Kindle Oasis 1 does not have that flickering at all, but Forma has it from 7% to 100% except 67% for some reason.

But I can't say it is somehow bothering me, most of time I read without front light at all or on very low level about 4-5%. And I can't see it without filming at all at any level.

Last edited by hel; 11-14-2018 at 03:07 PM.
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Old 11-16-2018, 01:00 AM   #29
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Video that shows flickering says nothing about how your eyes/brain perceive the device. I've been scouring Pubmed/Google Scholar looking for adverse neurological effects from PWM in display lighting and haven't been able to find anything. That's not evidence that it's zero in 100% of people but I am confident that it isn't a widespread problem at high & imperceptible frequencies.

Out of interest, pupillary light reflex latency in a healthy eye is around 250 ms. So the assertion I've read that adverse effects from high-frequency lighting PWM are caused by rapid oscillations of the pupils make no sense to me.
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Old 11-16-2018, 07:35 AM   #30
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I can see the flickering when I film an video at 240 fps slow motion.

By far, I didn't notice that it will cause me eye strain, maybe I didn't pay attention.
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