Dear esteemed Postfix users and experts!
First, let me apologize for intruding and discussing a Postfix unrelated
topic, but as a person whose health was affected by poor quality LCD
(and other) screens, I feel compelled to step forward and and provide a
few short pointers that could solve or at least mitigate Mr. Vybíhal's
problems.
First of all, here is how to change color scheme to inverted ("Dark") in
the popular browser Chrome (other browsers will have similar options,
but you will have to research them yourself):
Either install Chrome Extenstion called "Dark Reader", or simply open
this URL:
chrome://flags
, search all the settings (flags) for the word "Dark", and switch the
option called "Force Dark Mode for Web Contents" to "Enabled", or
experiment with the other options and see what fits your needs the most.
Note that modern Android devices (from Android 10 up) support switching
to system-wide Dark color schemes, because bright windows and GUI
elements cause burn-in on modern OLED screens, so you can take advantage
of that.
That being said, the most problems "hurting your eyes" come not from the
bright colors themselves (although choosing dark color scheme mitigates
the problem), but from the phenomenon called "screen flicker". Most LCD
and all OLED screens use a technique called PWM (Pulse Width Modulation)
to control brightness, because they capable of only two states - off
(black) and on on maximum brightness. PWM periodically switches on and
off the screen, creating the illusion of dimming the screen gradually
(although it, in fact, does not) - there is a set PWM frequency,
starting from 240Hz (very bad, severe flicker) to thousands of kHz that
should theoretically be harmless, except it often is not, and according
to your brightness setting, the screen is dark part of the cycle and lit
during the rest (for example if brightness is set to 50%, it's exactly
half and half. if set to 100 percent, the scree usually does not flicker
at all, staying on all the time).
The sensitivity to screen flicker caused by PWM is very individual -
some (lucky) people do not register anything, some (like me), have
swollen, red eyes, headaches and pain in the eyes. There is a reaeach
proving that similar to flickering light used by EEG, PWM flicker
affects human neural system directly, and may cause yet unknown health
complication (at the very least, it tires us faster).
Today, the problem is well known and documented, so you can choose a
monitor (or laptop) whose screen is certified "flicker-free", which
means it does not use PWM, but direct current to control brightness
(being and incandescent light source, at the expense of slightly worse
color reproduction and accuracy). Good review sites (Prad, FlatpanelsHD,
rtings, tftcentral and others) use oscilloscope to measure the PWM
frequency and comment on its type and severity (or absence if it's the
case).
For more information, please google PWM, there is ample reading in both
English and Czech.
Lastly, I apologize to everyone for this rather verbose contribution, I
will shut myself up again immediately and switch back to lurking. Please
don't ban me from the list for this, your expertise and diligence solved
me many problems as Postfix server administrator, I very much value your
knowledge and strongly wish to be able to read your contributions.
Best regards to everyone, and thank you!
-- Daniel Ryšlink
On 02-Jun-21 20:08, Charles Sprickman wrote:
On Jun 2, 2021, at 1:40 PM, post...@ptld.com wrote:
On 06-02-2021 1:35 pm, Josef Vybíhal wrote:
the background was changed to white.
curl -sI http://www.postfix.org/postfix.css | grep Last
Last-Modified: Sun, 20 Feb 2011 12:14:00 GMT
Any ideas why the background "to me" is now white when its been yellow for
years?
I tried in both ff/edge browsers to make sure one browser wasn't acting strange.
What color is the background to you?
The CSS doesn’t declare any background color, so it’s fully up to the browser
(or any local stylesheet overrides) to alter the color.
Can’t recall ever seeing it as anything but white before...
