Originally Posted by Jodiuh
LB sounds like it would be not so good for those of us sensitive to pwn flicker...right?
on what you are really truly sensitive to.
Some people are sensitive to 360 Hz PWM flicker, but never had eyestrain with 120 Hz CRT and didn't have eyestrain with 120 Hz LightBoost.
TFT Central also mentions in their article
that LightBoost has no PWM artifacts.
There are apparently several different reasons why eyestrain may occur with a modern LED monitor:
- Problem: Flicker Sensitivity
Some people are sensitive to flicker indirectly. Most people can't "see" flicker above approximately 75 Hz. However, a few people are more sensitive to flicker, at least by "feel" (headaches etc). People like you. Sometimes people don't see the flicker but get headaches anyway (indirect effect). That's why in many countries such as Canada, we have phased out old fluorescent light ballasts (120 Hz flicker) and now use electr ballasts (20000 Hz flicker) for fluorescent lights. As a result, headaches have dropped by 50% when switching fluorescent lights from 120Hz analog ballast to 20000Hz electronic ballast. See this article:
"Are there any health effects associated with light flicker?"
Clue: If you get headaches even with CRT @ 120Hz, don't get LightBoost. Otherwise, it can be a candidate.
Remedy: Get a PWM-free display if you get headaches even with CRT
Myself: I'm not sensitive to 120 Hz flicker.
- Problem: PWM Artifacts
Yes, that's the stroboscopic effect in action especially at lower brightness settings such as Brightness=0%. Using 360Hz PWM = triple image at 120Hz refresh, using 240Hz PWM = double image at 120 Hz refresh. A low frequency equivalent of this is the CRT 30fps@60Hz double image effect. However, PWM artifacts can be visible even at hundreds of Hertz. That said, if you have one flash per refresh, there are no multi-image artifacts (e.g. CRT, LightBoost). You can see artifacts during fast motion, such as during scrolling text or dragging a window; or moving objects in video games. One scientific way of testing is to use a motion test.
Examples of PWM artifacts are written about at:
Blur Busters: LCD Motion Artifacts 101
TFT Central: Pulse Width Modulation
Clue: You've never gotten CRT headaches or PWM headaches but your eyes see rough-looking motion blur and you get eyestrain after having gamed for a while.
Remedy: Get a PWM-free display, or enable LightBoost on your display
Myself: I'm sensitive to this, and these sometimes bother my eyes. Eye focus muscles can be strained by trying to focus on ugly-looking motion blur during fast motion. My eyes prefer either PWM-free operation _or_ PWM running at fps=Hz (one strobe per refresh), like a motion blur elimination backlight.
- Problem: Excessive Brightness
Some people do get PWM headaches. However, sometimes your headache is really because of excessive brightness instead. There were people who thought they had PWM headaches; but that their headaches mostly went away when lowering brightness (increased PWM); some LED monitors are still too bright even at 0% setting. (LightBoost settings of 50% and less is dimmer than non-LightBoost Brightness of 0%). People hear rumors about PWM headaches and they get headaches, so they think they have PWM headache when it's actually excessive brightness instead. New LED monitors are often so bright, that the brightness is what gives people headaches.
Clue: You've never gotten CRT headaches but you've gotten PWM headaches
Remedy: Get a PWM-free display that can dim very dramatically, or enable LightBoost on your display and adjust it to LightBoost=10% (dimmest setting)
- Problem: Excessive Brightness _AND_ PWM ("pick your poison" effect)
Catch-22 problem. Too much brightness? But you lower brightness, and now you get PWM. Ouch. If a person is simultaneously sensitive to excess brightness _and_ PWM, many of today's new modern LED monitors are often terrible for them. Sometimes a LED monitor at 0% brightness is still too bright; and you're getting a lot of PWM.
Clue: You get headaches with CRT's, with PWM, and with bright displays
Remedy: Get a PWM-free display that can dim a huge amount without PWM. However, if you never got headaches with CRT, then you might have been bothered by PWM artifacts; check "Problem: PWM Artifacts"
As part of running Blur Busters Blog and hearing testimonials about LightBoost, I get many dozen mixed answers; a very rough estimate is:
- over 50% of people said they had no effect; no eyestrain with LightBoost.
- under 25% said they had less eyestrain with LightBoost.
- under 25% said they had more eyestrain with LightBoost.
Some people are photosensitive, some people are color blind (approx 10% of population), some people are sensitive to flicker, some people don't have good 3D perception, everybody's vision system is different. The above list is not comprehensive; people can also get eyestrain from bad color, bad gamma, or even eyestrain from motion blur (especially if eyestrain only occurs during video games).
Most complaints were about LightBoost having poor color quality or being too dim; unrelated to eyestrain or headaches. Note, that LightBoost can be calibrated to recover most of the original color quality (via nVidia Control Panel), and using varuios crimson fixes already posted in some threads. Though it will always be dimmer than non-LightBoost operation. (when comparing LightBoost=100% versus Brightness=100%. LightBoost=100% is roughly as bright as Brightness=50%)
Dozens of people, including CallSignVega, say they hate PWM but like LightBoost.
The PWM story is full of surprises. The above post partially explains why.Edited by mdrejhon - 3/27/13 at 6:35pm