Alternative to f.lux for Ubuntu is Redshift

Update 2022: At least from Ubuntu 22.04 and Windows 10 onward, there's no need of installing redshift or similar apps, since the OS comes pre-installed with a NightLight app. Even Android has it.

 

Important: Blue light blocking lenses have been proven to have shown no evidence of preventing digital eye strain. Ref1, Ref2.

 

When using the computer in dimly lit surroundings, it helps to lower the brightness of the screen. One popular application for Windows was f.lux, and although they appear to have created a version for Linux, Ubuntu users don't need to install f.lux. We have Redshift.

Redshift can be installed hassle-free directly from the Ubuntu software center. Better still, don't even bother installing the GUI. Just install using
sudo apt-get install -y redshift

I was initially disappointed when Redshift didn't start because the computer wasn't connected to the internet and Redshift didn't start because it couldn't estimate my location (and hence the time of the day)...which made me wonder why it's programmed in such a dumb way.

Then I discovered that it's just a matter of using:
redshift -O 3000

You can change that 3000 to any other value, depending on your comfort.

Some laptops don't allow the brightness to go below a certain level (in which case you can also use xrandr), and the blue light from the screen is quite bright. Redshift creates an apparent reddish colour on the screen which is actually a bit comfortable.
Still better, you can even change the gamma with Redshift:
redshift -O 3000 -g .5

To remove the effect of redshift, simply type:
redshift -x

Inspite of this, I'd still recommend having ambient lighting, and not working in the dark. Even with Redshift, the monitor is bright and the surroundings are dark.

Alternative to Redshift and f.lux:

Every monitor has buttons for adjusting brightness and contrast. First, reduce the brightness and contrast to a level you are comfortable with. Then explore more of the monitor's menu options, and you'll see some color schemes. One of these will be a "warm" color. That's basically a color scheme that reduces the blue light. Just use that instead of installing redshift or flux or unnecessarily purchasing blue light spectacles that lie about reducing eye strain (because the real cure for eye strain is to stop overworking the eyes).


ps: Reports of digital screens making us lose sleep is a myth. We lose sleep because we force ourselves to stay awake. Not because of the digital screen's blue light. When you feel sleepy, just go to sleep instead of forcing yourself to stay awake longer.

Eye strain is not entirely due to digital screens

Disclaimer: I'm not a doctor. To get medical advice, please consult a doctor.

UPDATE: The real cure for eye strain: https://nrecursions.blogspot.com/2020/11/the-real-cure-for-eye-strain.html

My eye strain had become chronic in 2011 and I haven't fully recovered yet. During these years of crippling strain, I've been able to note subtle details which people ignore because their strain hasn't yet become serious. Also follow the links in "Other medical conditions" below.
Some facts:

Fact 1: Yes; reading text causes more strain to the eye compared to tasks that don't require extreme analysis on tiny areas. This doesn't mean that digital screens are the root cause of strain. Excess brightness of digital screens can slightly increase strain, but that's not the root cause of strain. (Important: Blue light blocking lenses have been proven to have shown no evidence of preventing digital eye strain. Ref1, Ref2)

Fact 2: The strain by itself is not an issue. It happening on a daily basis is not the real issue either. The real issue is that (assuming you don't have other medical problems) no matter how much you think that you are getting enough sleep, you actually aren't. If you get sleep your eye muscles will recover while sleeping and your strain is unlikely to build up to a stage where it hampers you.

Fact 3: When your eyes are strained, washing your eyes or wearing special spectacles or having coatings on spectacle lenses or looking at far away objects or exercising your eye muscles do not help. What helps is keeping your eyes closed until the strain subsides, and relaxing your neck and face muscles.

What to check for:

• Sleep: If you are confident that you are getting enough sleep, that's your biggest mistake. Very seriously and thoroughly evaluate yourself on whether you are getting a minimum of 7 to 8 hours of continuous, deep sleep every night. I stress on "continuous, deep". Waking up at night to urinate or being woken up by noise (even if you go back to sleep immediately) or sleep apnea or waking up due to stomach discomfort or waking up after 4 hours of sleep and being unable to go back to sleep etc. are signs that you aren't getting enough sleep. Keep a diary where you write the approximate time you slept and woke. You'll be surprised. Feeling sleepy many times during daytime is a clear indication that you lost sleep at night. Lying in bed awake with your eyes closed does not count as sleep.

• Other medical conditions: Astigmatism or deficiencies leading to dry eye (the beginning stages of eye strain can make you feel like your eyes are dry. It does not necessarily mean you have dry eye) or other medical conditions might be a problem, but verify your sleep sufficiency before blindly accepting what the doctor says. Getting second opinions is not guaranteed to give you the right diagnosis. I met twelve ophthalmologists who didn't have a clue of what caused my eye strain and how to cure it. I have been shocked and disappointed at this (also reported by another person, though I don't agree with his diagnosis). There are some doctors though, who actually are experienced enough to identify the problem and carefully examine your medical history and symptoms before they come to a conclusion. Find these doctors. The general physician or ophthalmologist may not always be knowledgeable enough to identify certain highly specific conditions certain people go through. Some examples are here, here, here, here, here, here, here, here, here and here.

• Food and water: It's medically known that stomach problems cause sleep problems and sleep problems cause stomach problems. Both of these wreck havoc on the rest of the body. I've listed what precautions to take with food in this post.

• Spectacle lenses: Glass lenses were much less strenuous for me. I believe it has to do with the better visual acuity it provides. Having special coatings on the lens didn't help reduce my eye strain. Using cheap, ordinary glass lenses without any special coatings gave me the most relief and I eventually started using the computer without wearing spectacles for a while. Haven't tried contact lenses and am definitely not going for Lasik inspite of the rebuttal because the focus should be on proper food, rest and sleep.

How to fix fatigue-induced eye strain

• Step 1: My doctor prescribed eye drops and Lacrigel to give some initial relief. These were only for a few weeks of use just to give some initial relief. They won't solve the problem and are not meant to be used forever. Make sure you close your eyes for a while everytime your eye feel strained. 

• Step 2: Rule out medical conditions sensibly. A dry eye specialist tried convincing me I had dry eyes and recommended a vitamin B12 test at an affiliate lab and a followup consultation, but a Schirmer's test at another hospital ruled out dry eyes. Computerized eye tests at two hospitals and three ophthalmologists said I had astigmatism because I mentioned eye strain, but those glasses caused unbearable strain and two other ophthalmologists later ruled out astigmatism. Basically, get opinions from multiple doctors to ensure that you have been diagnosed correctly and ensure you verify if you really have a medical problem or if it's just plain fatigue-related strain. Ophthalmologists themselves have told me that vision correction is not an exact science and that mistakes are possible.

• Step 3: Examine what food you eat. If you eat from an office/college canteen, bakery, stall or a restaurant (or even if your cook at home doesn't cook properly), chances are very high that you are eating food that is either not fully cooked or has burnt particles in it or is of poor quality or is adulterated. Trust me, a majority of people in this world (including you) are very very poor judges of food quality. Drinking curd after dinner helps give some relief and your sleep should improve with time (probably because curd has Tryptophan) as you change your food habits to eating properly cooked food. More here.

• Step 4: Make sure you get 8 hours continuous sleep every night. Don't let people or a phone wake you unnecessarily. Don't let your job make you lose sleep. Make sure you have a quiet, warm, dark, comfortable environment for sleeping. And please take Step 3 very seriously.

• Step 5: Make it a point to close your eyes and relax your face muscles everytime you feel even a slight bit of strain. Don't push yourself to work harder unless you have got your rest first. No job, boss, career, pay or recognition is worth as much as health. I learnt that the hard way.

• Step 6: Get a good amount of full-body exercise. Exercising does not help reduce eye strain at all. It however does help in maintaining good health which could give you slightly improved sleep and general body function. Oh by the way, when your muscles are aching from exercise at the gym, are you supposed to take rest or fix the ache by exercising more? Take rest obviously! Same way, when your eyes are strained, just close your eyes and rest them.

All you really have to know is that unless you have some underlying medical condition, simple fatigue-induced eye strain can be cured just by getting your eight hours of sleep and some rest when your eyes are tired.  It can take a few months/years to recover (and nothing other than rest+sleep can help speed up the recovery), but that's all there is to it. You don't have to spend a fortune on special spectacles or medication. Take care.

Remember: The primary focus should be on getting well cooked food, rest and sleep.