# Eye strain from certain video modes/drivers



## foster (Oct 5, 2015)

Hello,

I get eye strain from some graphic cards and certain video modes.
Maybe you have more technical knowledge than I do, and you can help me find the cause.
I already tried other operating systems and know which ones I can use without problems, but if it is possible to fix the eye strain I would like to make FreeBSD my main OS.

This is what I tried so far with FreeBSD (and Xfce):

NVIDIA Quadro NVS 295 (DisplayPort):

no eye strain in text mode
no eye strain in X using nv driver
eye strain in X using nvidia driver

Intel integrated graphics GMA 3100 (VGA):

no eye strain in text mode
eye strain in vt default graphic mode
eye strain in X using Intel i915 driver

I would use nv, but it is terribly slow.

My question is: what might be the differences between nv and nvidia/i915?
Do they use different timings, video modes...

I disabled temporal dithering in nvidia-settings and in /etc/X11/xorg.conf, but it did not help. In another thread I try to disable dithering in the Intel driver, just for testing purposes.

If only I knew what the technical difference was between the drivers' display output, it might put me on the right track.
Do you have any ideas?


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## shepper (Oct 5, 2015)

Your eye can change focus (accomodation) and far-sighted individuals easily focus on distant objects and have to strain to see close objects.  It is more likely that glasses would help.  Simple magnifiers will bring your depth of field/focus closer but if you can afford it, I would recommend an evaluation.  As a side note, my father was an airline pilot and had to see out the window, the instruments/gauges and overhead controls.  By the time he retired he had trifocals.


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## foster (Oct 6, 2015)

The glasses theory won't explain why there are no issues with the nv driver. Or why there are other totally working OS/driver/graphics cards combinations.
No, it is definitely not more likely that glasses would help. I understand your point though.
You see, it is not the first time I stumble into this problem. There are other people who have similar problems with different hardware and video modes. It started a few years ago with Macbook Pro backlight issues. It is probably the biggest thread in the Apple Forums with hundreds of pages and still expanding. We are in touch via the Internet and we already found that pulse width modulation (in display [back-]lights) and temporal dithering in graphics drivers and even monitor firmware are major reasons for eyestrain. The problem is that only a minority of the population seems to be severely affected. And that leads to disbelief.
So I am used to skepticism, but I would like to focus on technical facts here. I hope you understand.


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## shepper (Oct 6, 2015)

Well, here is the technical definition of eye strain.


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## wblock@ (Oct 6, 2015)

Rather than guessing, run `xrandr` with both drivers and find out exactly which video mode is being used with each driver.  Then consider switching to hardware with open drivers where there is the possibility of actual control over it.


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## SirDice (Oct 6, 2015)

You may want to take a look at the various refresh rates. A low refresh rate would have more "flicker" and thus more strain. Steer clear of VGA, it's an analog connection so it's always a bit 'fuzzy'. Preferably use a digital connection like DVI, HDMI or DisplayPort. These also support higher refresh rates than VGA ever could, provided your monitor can handle it of course.


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## foster (Oct 10, 2015)

Xrandr showed the same video mode on all drivers. That is 1920x1080@60Hz, progressive. There must be something else going on, maybe the temporal dithering settings are not applied as they should. Or some other source of flicker that is non-obvious. I am out of ideas.


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## shepper (Oct 11, 2015)

Could it be backlighting?  From the Arch Linux


> *NVIDIA settings*
> Users of NVIDIA's proprietary drivers users can change display brightness via the nvidia-settings utility under "X Server Color Correction." However, note that this has absolutely nothing to do with backlight (intensity), it merely adjusts the color output. (Reducing brightness this way is a power-inefficient last resort when all other options fail; increasing brightness spoils your color output completely, in a way similar to overexposed photos.)


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## foster (Oct 13, 2015)

I just realized the "working" modes that I marked green in my first post have something in common. They don't use hardware acceleration. Do you know of any differences in the video signals when hardware acceleration is used? Even the smallest difference might matter, so please reply if you know something.

If I get the time I could test the other graphics drivers without hardware acceleration. The only way I know of to turn it off is to add _"Option" "NoAccel" "True"_ to the device section in xorg.conf. Is that a universal option or something driver specific? I found this option for the Raspberry Pi in a link in the FreeBSD wiki, and in the Intel driver's manual page at www.x.org.

I just fear that even if that works, all drivers might be equally slow.
I wonder if newer CPUs have enough power to render anything in software mode fast enough so that you won't see a difference, even when scrolling complex websites. My current CPU (Core 2 Duo 2 GHz) is too slow for that.


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## SirDice (Oct 14, 2015)

foster said:


> The only way I know of to turn it off is to add _"Option" "NoAccel" "True"_ to the device section in xorg.conf. Is that a universal option or something driver specific?


Not entirely sure as I've never needed it but I do believe this is a "universal" option that works for all Xorg drivers. So it should also work with the NVidia drivers.

The old NVNews forums had a specific section for FreeBSD NVidia drivers that was frequently read by NVidia developers but the whole forum is gone now. NVidia does have its own forums but I'm not so sure about their help with FreeBSD drivers issues. There's no sub-forum for it. But it probably won't hurt to ask them about it if you notice a significant difference. After all, they're the ones that wrote the driver


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## kammerer (Sep 3, 2019)

foster said:


> I just realized the "working" modes that I marked green in my first post have something in common. They don't use hardware acceleration. Do you know of any differences in the video signals when hardware acceleration is used? Even the smallest difference might matter, so please reply if you know something




foster, can you use FreeBSD 11 or 12 (and in which configuration)? Actually I'm getting eye strain on any graphics card (nvidia, ati, intel) and driver.
_"Option" "NoAccel" "True"/"Option" "Accel" "False" doesn't solve my issue_


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## SirDice (Sep 3, 2019)

kammerer please look at the dates, this thread is almost 4 years old. The OP hasn't been seen since 2016.


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