Your pupils contract because you are being overwhelmed be the amount of light coming out of your monitor. This doesn't sound so relaxing to me ;)
On the other hand, you could be myopic and under-corrected - and so suffer more when the pupils are relaxed (similar to the Night Myopia effect).
I do find it almost impossible to use dark background IDEs (such as XCode and Eclipse), because of the other GUI elements cluttering the screen (which are usually light). And this causes a lot of eye strain, because the amount of incoming light is still huge, while most of the screen is dark, relaxing the pupils and burning the retina.
Since most of my time I'm on Emacs or the terminal, I'm cool. Switching to a browser still hurts - one more incentive not to look at Hacker News while working ;)
> On the other hand, you could be myopic and under-corrected - and so suffer more when the pupils are relaxed (similar to the Night Myopia effect).
This is really interesting. I am severely myopic and have always preferred a black background.
However, last week I had cataract surgery and now with a +27.5D (!!) IOL implant in my right eye - the only eye I have, I'm not so nearsighted as I used to be (20/80 now instead of 20/200), but I am still experiencing eye strain when looking at the computer for any length of time. After switching my editor to a white background, things got a lot easier to see.
Mind you, I am only a few days post-surgery and I haven't yet gotten new glasses. I was also having a lot of issues with colorblindness and contrast sensitivity, as well as a lot of "double" vision (which was more accurately "I see 8 of those things" vision). These are now resolved, as well. All of those will factor into the equation a great deal, I'm sure, but I do find that after the cataract surgery, the light background makes for less eye strain.
I switched color schemes from "Blackboard" to "Dawn" but my Blackboard theme may have been modified a bit. I've been using it for so long, I can't remember. It almost seemed as though there were too much contrast with the dark background.
I'm still not at a point where I can use the computer for more than about an hour at a stretch. It's amazing how mentally and physically taxing adjusting to better vision can be.
Not myopic, but I do have some eye problems that limit the correction I can get. This may make me in the minority, but it also means that dark background defaults are not a positive experience for me. Text on light backgrounds is is crisp, while dark backgrounds looks like it's been badly anti-aliased.
With regards to brightness of the monitors, I keep it reasonable - about 25% of what the monitors could do.
When I have no choice, I also tone down the brighness to ridiculous low levels. On some monitors, even 0% is too bright (hint: change the contrast then, some monitors will dim the backlight some more).
I am not a doctor, so I am mostly speaking from experience.
My eyesight without glasses is bad enough (nowadays) that I can't do a fair comparison of uncorrected vision between dark and light (can't read anything either way), but letters on dark background get significantly more blurred than with a light background. The overall room lighting level also seem to play a large role. Hence, pupil size.
My guess is that not only myopic individuals, but people with any visual problems due to their corneal shape. Also LASIK patients with large pupils (but that's to be expected).
Again, not a doctor. I am hoping some doctor will step in and comment :)
On the other hand, you could be myopic and under-corrected - and so suffer more when the pupils are relaxed (similar to the Night Myopia effect).
I do find it almost impossible to use dark background IDEs (such as XCode and Eclipse), because of the other GUI elements cluttering the screen (which are usually light). And this causes a lot of eye strain, because the amount of incoming light is still huge, while most of the screen is dark, relaxing the pupils and burning the retina.
Since most of my time I'm on Emacs or the terminal, I'm cool. Switching to a browser still hurts - one more incentive not to look at Hacker News while working ;)