f.lux & Night Light vs Monitor Calibration: Can They Coexist?
f.lux and Windows Night Light shift your screen warm at night. DisplayCAL tries to keep your screen exactly on target. Do they fight? The short answer: turn the night filter off while measuring, and they can coexist the rest of the time — with one vcgt caveat you should know about.
Q1: Must I turn off f.lux / Night Light when calibrating?
Yes — absolutely, no exceptions. Night filters work by shifting the white point away from your calibration target (typically toward 3400–4500 K after sunset). If one is active during measurement, DisplayCAL will faithfully calibrate a screen that is mid-shift: your brightness, white point, and gamma readings will all be wrong, and the resulting profile will describe a display state that only exists at that exact minute of the evening.
Before starting any DisplayCAL session:
- f.lux: right-click the tray icon and choose Disable > for 1 hour (or longer than your session), or quit f.lux entirely.
Q2: Can I use the night filter normally after calibration?
Yes. Once the profile is built and the Profile Loader has applied the vcgt, a night filter just does its usual thing on top: it warms the image for your eyes at night. That’s its job, and it doesn’t damage or invalidate the calibration — it temporarily deviates from it, by design, and returns to the calibrated state when the filter turns off in the morning.
One honest caveat for color-critical work: while the night filter is active, your screen is not in its calibrated state, so don’t do final color judgments at 11 pm with f.lux at 3400 K. For evening photo editing, disable the filter for the session.
Q3: What if f.lux and the Profile Loader fight over the video card?
Both tools write to the graphics card’s gamma table (vcgt): the Profile Loader loads your calibration, and f.lux applies its own adjustments on top. Normally they stack without drama. But if colors ever look wrong — washed out, or the calibration seemingly “lost” — after f.lux changed state, the two may have stepped on each other. The recovery order matters:
- Disable f.lux / Night Light completely.
If this happens repeatedly, the practical fix most users settle on is scheduling: let f.lux do its thing in the evening for comfort, and disable it during any color-critical work. See our Profile Loader guide for how the loader applies the vcgt, and multi-monitor matching if you run mixed setups where one screen uses a filter and another doesn’t.
DisplayCAL user’s night-filter checklist
- Night filter OFF before every measurement session — check the tray icon, not just your memory.
Frequently Asked Questions
Do I need to uninstall f.lux to use DisplayCAL?
No. You only need it disabled during measurement sessions. f.lux and DisplayCAL coexist fine the rest of the time — just remember that an active night filter means the screen is deliberately not in its calibrated state.
Does Night Light ruin my ICC profile?
No. The ICC profile is a file describing your calibrated display; a night filter doesn’t modify the file. It only changes the live output on top of the calibration. Turn the filter off and the calibrated state is exactly as it was.
Why do my colors look washed out after f.lux turns on at sunset?
That’s the two tools interacting at the vcgt level: f.lux applies its warm shift on top of your calibration. It’s usually normal behavior, not corruption. If it looks broken rather than just warm, disable f.lux and reload your profile via the Profile Loader.
Should I calibrate during the day or at night?
Either is fine as long as the night filter is off and ambient light is controlled. Many photographers prefer a dim, consistent room in the evening — which is exactly when f.lux wants to activate, so double-check it before you start measuring.