Author Topic: Tablets/iPads Flicker-free and Safe for Epileptics?  (Read 409 times)

Tablets/iPads Flicker-free and Safe for Epileptics?
« on: September 14, 2020, 10:37:52 am »
Just that, really.

I have a client who would really benefit from such an electronic device, but would only be able to use one if it was flicker-free and did not pose a risk of provoking a seizure.

Any advice gratefully received...

Re: Tablets/iPads Flicker-free and Safe for Epileptics?
« Reply #1 on: September 14, 2020, 11:53:05 am »
Can't offer official advice, can only talk from point of view of someone who used to suffer flicker-induced migraines (with occasional mini-seizures).

the higher spec, the better. So better resolution = less flicker.

Most devices have a blue-filter mode. This reduces screen glare a lot and correspondingly the impact of flicker.

<i>Marmite slave</i>

Re: Tablets/iPads Flicker-free and Safe for Epileptics?
« Reply #2 on: September 14, 2020, 12:01:03 pm »
Tablets generally have the same kind of screens as phones and laptops, so if they can use those a tablet will be fine.

OLED screens have a small amount of high frequency flicker, but are rarely found on tablets. No iPad has one.

Kim

  • Timelord
Re: Tablets/iPads Flicker-free and Safe for Epileptics?
« Reply #3 on: September 14, 2020, 12:14:58 pm »
It's a minefield.  The problem comes where LED brightness is varied using Pulse Width Modulation, resulting in a flicker at the PWM frequency whenever the screen is used at anything other than 100% brightness (the flicker will be most obvious at 50%).  Typically that's in the 200-400Hz range, which is far too low, and results in visible artefacts (as well as potentially causing eye-strain, migraine, etc).

OLED displays and most LCDs using an LED light source as the backlight are afflicted.  It's entirely possible to drive an LED backlight without flicker (or with flicker in the tens of kilohertz that's actually undetectable by humans, rather than undetectable by some subset of particularly unobservant humans), and some do that.  This is starting to become a thing that monitor manufacturers are mentioning in their marketing material, but I don't think that's tricked down to fondleslabs, so there's no way of knowing how flickery a given screen is from the specs - they simply don't mention it[1].

Pragmatically, the only way to find out if a screen is flickering is to test it (remembering not to have it at full brightness!).  If your eyes/brain are suitably sensitive, it should be obvious.  If they're not, you may be able to perceive shutter artefacts by twanging an elastic band or rapidly waving a finger or pen in the light of the display.  Otherwise, you'll need electronics to detect it.

(This all goes for LED lightbulbs too, only they tend to flicker more obnoxiously at double the mains frequency.)


[1] Don't confuse backlight flicker with display refresh frequency.
Careful, Kim. Your sarcasm's showing...

barakta

  • Bastard lovechild of Yomiko Readman and Johnny 5
Re: Tablets/iPads Flicker-free and Safe for Epileptics?
« Reply #4 on: September 14, 2020, 01:50:57 pm »
Sadly a lot of people who are sensitive can't SEE the problem like I can and it takes some hours or whatever for the usage to build up to causing problems, cos it's subtle.

I haven't seen any iThings lately to give a personalised comment as someone who reliably picks up flicker below 2kHz. I hate Kim's tablet (which is not an iThing) but my MotoG phone is fine for example.

Re: Tablets/iPads Flicker-free and Safe for Epileptics?
« Reply #5 on: September 14, 2020, 01:58:26 pm »
I think that you can pick up flicker using a mobile phone camera. Just tried it on my laptop screen; to me, the screen looks steady, no flicker. Via the mobile phone camera, there is a very obvious strobing travelling bottom of screen to top.
<i>Marmite slave</i>

barakta

  • Bastard lovechild of Yomiko Readman and Johnny 5
Re: Tablets/iPads Flicker-free and Safe for Epileptics?
« Reply #6 on: September 14, 2020, 02:20:37 pm »
Depends... My current mobile has a flicker suppression mode that seems hard to turn off. It can pick up 100Hz ok, but it misses some of the higher range.

It's also hard to tell if all epileptics are sensitive in the same way we are, there's legally accepted epilepsy trigger factors but are they enough?

Kim

  • Timelord
Re: Tablets/iPads Flicker-free and Safe for Epileptics?
« Reply #7 on: September 14, 2020, 03:27:13 pm »
I haven't seen any iThings lately to give a personalised comment as someone who reliably picks up flicker below 2kHz. I hate Kim's tablet (which is not an iThing) but my MotoG phone is fine for example.

Samsung Galaxy Tab S3, which has an OLED display.  I can see the flicker, but it doesn't bother me.  (Same goes for the Iiyama monitor I'm writing this on right now.)
Careful, Kim. Your sarcasm's showing...

Kim

  • Timelord
Re: Tablets/iPads Flicker-free and Safe for Epileptics?
« Reply #8 on: September 14, 2020, 03:29:53 pm »
It's also hard to tell if all epileptics are sensitive in the same way we are, there's legally accepted epilepsy trigger factors but are they enough?

Indeed.  In this case I'd also be worried about effects from brightness changes at much lower frequencies than the backlight PWM.  Moving images (particularly animated advertising and computer games) for example.
Careful, Kim. Your sarcasm's showing...