Feature Request: Intensity/Opacity adjustment



  • Dear forum,

    I am really pleased to have found this program. I got accustomed to a similar program for my Samsung Android Smartphone called Twilight which really pleases me. Having bought a Windows laptop recently I was looking for a similar app for Windows and found f.lux the best.

    Even though I think f.lux works very well already, I'd like to suggest a feature to possibly make it even better. Twilight for Android has this feature and it really pleases me. They call it intensity (which has nothing to do with brightness/dimming!)
    Twilight enables you to 'change the screen-color' in thee ways:

    1. Color temperature
    2. Intensity
    3. Screen dim

    Intensity seems to operate just as the opacity setting in programs like Gimp/Illustrator. It leaves the color temperature the same and let's you change how opaque the color is.

    On my smartphone I have set the following values: Color temperature 1900K, Intensity 80% with different brightnesses (Samsung Amoled on Galaxy Note 2) . When I compare that to f.lux 1900K with different brightnesses (IPS display on HP Elitebook Revolve 810) both screens are really pleasing to the eyes, but screen on my smartphone shows the whites much more white, and boost a better contrast which I much prefer over the laptop screen which has an overall very reddish color..
    Don't get me wrong, I do understand why the screen should show reds, but I think being able to change the opacity will make the use of f.lux even more pleasant and easily adjusted for all demands.

    Here's a link to the best video I found that shows how it works (commentary is in Dutch, but it does shows what happens when you change 'intensity')
    https://youtu.be/H4_8YNVpAgo?t=45

    Kind regards to all who helped developing this program!


  • f.lux team

    I believe this approach is one of the worst things you could do to a screen.

    Twilight's default setting is called "1500K" but actually measures 5100K, which perhaps explains why you are seeing it as "more white", because the number is not real. f.lux makes extremely accurate colors, and so the comparison is difficult to do by eye, because you are comparing two settings that are unrelated.

    For comparison, here are our measurements of twilight's default settings:
    https://fluxometer.com/rainbow/#!id=Nexus 4 Apps/twilight1500-nexus4

    f.lux maintains most of your screen contrast - we preserve the native black point exactly, and in doing so, we preserve a large percentage of visual contrast, allowing use in darker rooms, and also improving your eye's ability to adapt to color changes.

    Display manufacturers have worked hard for years to achieve white:black contrast ratios of 1000:1 and greater, and using Twilight to reduce this to 5:1 is just very silly. In doing so, you will actually wind up keeping your screen brighter (you will dim it less) in order to keep the screen readable.

    The "transparency" control has no equivalent in f.lux, because we never reduce contrast by boosting black levels. This control is all about how much extra light to put into the blacks, and we do not and will not do this. If you have extra contrast to burn, dimming your screen is probably a better idea.

    Also, color adaptation (perceiving "white") depends to some extent on the "surround" light - if you are in a room without very dim incandescent, you probably will see any f.lux setting below 2700K as "orange". If you want a whiter screen, our recommendation is to dim the display and use a higher color temperature setting instead.



  • My recommendation will take it further: use warmer room lighting, in terms of color temperature - aim for the warmest color that you can get. I also strongly recommend aiming for the dimmest light possible as well, especially in the hour or two (or three, if you want) before going to sleep.

    I have made another observation with room lighting, and I'd like to share it as a critical part of my recommendation: the lower the physical height is of your indoor light sources (such as a desk lamp vs. a ceiling light), the easier it will be to relax and begin feeling sleepy at night when using only these "lower" lights. I think the reason why is, it simulates the lower position of the sun in the sky. We have millions of years of evolution where the only source of light - the sun - gets physically lower in the sky at night while also getting warmer in color, emitting less and less blue light - and also getting dimmer. So, the more accurately we can simulate this indoors, the easier it will be to go to sleep.

    So, if you're going to be sleeping soon (like in an hour or two or so) but you're still using your computer or tablet or whichever, then combining this entire recommendation that I just made in both paragraphs above with the warmest color in f.lux and the lowest display brightness will almost be magical in how well it can work. I'm speaking from experience here.

    You see, my ceiling fan's light kit can go extremely dim - that's one of the reasons why I bought it. I have warm-colored incandescent bulbs in it too, on purpose. However, there's one thing that I didn't know until I experienced it: even at the dimmest setting, it still feels alerting even though it's impractically too dim! I mean, even after my eyes have fully adjusted, it's still too dim at its lowest setting. The color temperature appears to be very warm too, so at first I was confused as to why it still felt very alerting.

    I realized after experimenting that this is because it's very high in my "indoor sky". I mean, it's directly overhead, just like it's high noon but with a near-total eclipse. So, I never use the dimming feature. Ever. It's useless to me. Sigh. lol The experiment that lead to this discovery was, I turned the fan light off and turned on my little 3-way touch desk lamp that has a simple 40W incandescent bulb, and I immediately felt a difference and I started yawning. I still do to this day. Every. Single. Time. Without fail.

    After this discovery, I began noticing that this is true everywhere I go, at anyone's house, in restaurants, etc. etc. etc. The location of the light source in the "indoor sky" will partly dictate how alerting that light is, or how relaxing it is. Of course, there's also the color temperature and brightness, but that goes without saying. :) So yeah, when I'm getting ready for bed, I avoid lights that are high up in my indoor sky. In some parts of my home, I don't have a choice but to use lights that are high up, so I have done everything I can with dimmers and the warmest incandescent bulbs I could find, which ended up being the awesome 20,000-hour bulbs made by Aero-Tech. Check them out. On a dimmer, they can almost become orange. I love it.

    I apologize for the length of this post by the way, but I feel that this is very important stuff.

    Edit: I actually envision a future where homes will be built with indoor lighting that accurately simulates an entire day from sunrise all the way to sunset, complete with color temperature, brightness, and the physical location of all the light sources in the "indoor sky". I also envision these homes to have the ability to block 100% of all outdoor light for people who need to sleep during the day.



  • For comparison, here are our measurements of twilight's default settings:
    I had no idea about the Nexus 4 apps! Is this new?

    Also yes, lower height light sources work so much better!


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