Jack Richards
Founder, Sundown
Jack builds tools that protect your biology from your technology. He created Sundown after spending years researching PWM flicker, temporal dithering, and circadian disruption on modern displays.
Articles by Jack
How to Turn On Night Shift on a Mac (and Off Again)
How to turn on Night Shift on a Mac, schedule it for the evening, make it more or less warm, and turn off night mode, following Apple's own steps.
Do Blue Light Glasses Work? Glasses vs Screen Warmth
Do blue light glasses work? Cochrane found they may not ease eye strain, and the sleep trials used tinted lenses worn for hours. What that means for a Mac.
Color Temperature Explained: What Kelvin Means for Your Mac
Color temperature explained: why 6500 K counts as daylight, what a 2700 K screen does to its blue channel, and what melanopic light research does show.
Computer Vision Syndrome on a Mac: What the Research Says
Computer vision syndrome is mostly about blinking, focus and dry eye, not your screen's color. What the research says about causes, remedies and your Mac.
Dark Mode vs Night Shift vs True Tone on Mac
What does Night Shift do on a Mac, and how is it different from Dark Mode and True Tone? Three switches, three jobs, and what none of them does after dark.
Delayed Sleep Phase and Your Mac Screen at Night
Delayed sleep phase needs a clinician. What the one glasses trial in DSPD patients found, and an untested Kelvin example for a night owl's Mac screen.
Does Dark Mode Reduce Blue Light? What We Measured on a Mac
Dark mode cuts how much light your Mac emits, but not its colour. We measured macOS system colours to show what it changes, and what it leaves for night.
Screen Time Before Bed: A Mac Evening Routine by Kelvin
Screen time before bed, done better: what the eReader and room-light studies found, and a two-hour Mac routine with the Kelvin to set at each step.
Shift Work Sleep and Your Mac Screen: A Kelvin Guide
Shift work sleep disorder needs a clinician. Your Mac screen needs a plan: the Kelvin to set before your sleep window on nights, lates and rotating shifts.
f.lux for Mac: How to Download It, and What Happened to It
f.lux still installs on a Mac, and its shipping binary is dated 17 May 2023. Where to download it, how to set it up, and how to check that date yourself.
Best Blue Light Filter for Mac 2026: Night Shift vs f.lux vs Sundown vs CircadianShield
Night Shift, f.lux, CircadianShield and Sundown compared on filter depth, PWM flicker protection, privacy and price. The full side-by-side test.
MacBook Pro Yellow Screen: Why It Looks Yellow and How to Fix It
A yellow MacBook Pro screen is almost always Night Shift, True Tone, a filter app or a colour profile. How to find which one, and how to turn it off.
Best Blue Light App for Mac in 2026: Night Shift vs f.lux vs Iris vs CircadianShield vs Sundown
Five Mac blue light apps tested on lowest Kelvin, PWM flicker, dithering, privacy and price: Night Shift, f.lux, Iris, CircadianShield, Sundown.
Blue Light Filter for Computer Screen: Which Type Actually Works?
Software filters, physical screen overlays and built-in modes all work differently. What each one actually does to your display, and how to choose.
PWM Monitor Flicker: Why Your Screen Hurts (And How to Fix It)
Monitors dim by strobing the backlight thousands of times a second. Most people never see it and some get headaches. How to test for PWM and stop it.
Best Circadian Health Apps in 2026: 9 Tools That Actually Work
Nine circadian apps for 2026 across display filters, sleep trackers, light therapy and chronobiology, each tested against the research behind it.
Best Screen Dimmer Apps for Mac in 2026: 6 Tools Compared
Need your Mac dimmer than the minimum brightness allows? Six dimmer apps tested on flicker, eye comfort and how far each one actually goes down.
How to Reduce Eye Strain on Mac: 7 Settings to Change (2026)
Dimming a Mac screen can increase invisible flicker, and Night Shift stops at 2700K. Seven settings that change how your screen is lit and colored.
Blue Light Filter for MacBook: Beyond Night Shift (2026 Guide)
Night Shift stops at 2700K, which is where most MacBook guides end. Here is how to take the display down to 500K deep red, and what changes.
Best Mac Display Health App 2026: Complete Guide
Mac display health comes down to four things: blue light, PWM flicker, temporal dithering and scheduling. Every app tested against all four of them.
Night Shift Alternative for Mac: Why Apple's Built-In Filter Isn't Enough (2026)
Night Shift stops at 2700K and will not go warmer. Here is what a Mac looks like at 500K deep red, and the alternatives that actually get there.
Sundown vs Iris for Mac (2026): What Happened to Iris and What to Use Now
Iris pioneered deep filtering and PWM protection on the Mac. Here is how Sundown compares on depth, flicker, dithering and the upkeep we could verify.
f.lux Alternative for Mac (2026): What Replaced It
f.lux has not shipped a Mac update since May 2023: no macOS 26, no M4 tuning. Here is what replaced it in 2026, compared on depth and upkeep.
Mac Blue Light Filter: 3 Methods That Actually Work (2026 Guide)
Three ways to filter blue light on a Mac: Night Shift at 2700K, f.lux at 1200K, or a 500K deep-red app. Setup steps for each, and how to choose.
Blue Light and Sleep: What Your Mac Display Does to You
Evening screen light suppresses melatonin and pushes your body clock later. What the research shows, and how far a Mac display can be shifted.
How to Make Mac Night Mode Darker — Beyond Dark Mode
Dark Mode only darkens windows. Night Shift stops at 2700K. Here are the three settings that take a Mac screen down to 500K deep red, in order.
Red Screen Filter for Mac: Deep Red at 500K
Most Mac red screen filters stop at amber. Here is what 500K deep red actually looks like, why the number matters after dark, and how to set it up.
Display Dithering on Mac: The Hidden Flicker Source Your Blue Light App Won't Fix
Every Apple Silicon Mac flickers at the pixel level through temporal dithering. It is not PWM, most people never see it, and one Mac app stops it.
Flicker-Free Mode for Mac: How Sundown Dims Through Gamma Instead of the Backlight
Your MacBook dims by strobing its backlight thousands of times a second. Flicker-free mode holds the backlight at full power and dims through gamma.
How to Reduce Blue Light on MacBook Pro: 6500K to 500K
Night Shift is step one, not the answer. Every way to cut blue light on a MacBook Pro, from display settings to apps to room light, ranked by depth.
Fix Screen Flicker Headaches on MacBook (2026 Guide)
MacBook flicker headaches come from two invisible sources: PWM backlight dimming and Apple Silicon temporal dithering. How to tell which, and fix it.
Night Shift vs f.lux on Mac (2026): Full Comparison
Night Shift stops at 2700K, f.lux reaches 1200K, and neither touches PWM flicker. Compared on depth, scheduling, privacy, and macOS support.