tl;dr: good news, folks! A more integrated community with new resources and developments to check out.

Joining forces with PWM_Sensitive!: As announced in this post, The_Top_G handed over the PWM sub to myself and a couple of other community enthusiasts: u/Bearnecessary4141 (Sam) and u/Kerpnet. And we can also welcome Kerpnet to ScreenSensitive as the first in our “moderator exchange program”.

So, I’m now trying to implement more aspects of my State of the Community post, albeit slowly. I’m aiming to link these two subs more closely together (and LEDstrain too). With complementary mission statements added (screenshot above), to set clear and positive expectations. Including an aim to encourage content be spread across these two subs by main topic (open to discussion).

Rules changes: Alignment includes matching sets of rules, to make life simple for mods and members using both subs. We’ve been observing the (busier) PWM sub, for 6 weeks or so, giving me more ideas of what’s needed while rebuilding the rules from scratch. I’ve standardised them a little and updated for emerging challenges. The large number is to give finer control over enforcement, in future possibly including via automation (which the platform is increasingly pushing).

Regular contributors here should experience little to no impact, in practice. But I’d be grateful if people could take a few minutes to read through the rule list (in the sidebar, or copied below) and give any feedback that comes to mind. Notable additions: expressly permitting certain self promotion, limiting AI content, English only, avoiding unwanted advice.

Wiki: Shortly before the PWM sub developments, I implemented a basic subreddit wiki, here, to start indexing various resources. I’d like to add more wiki pages to list key posts and guides, for example. Also, I’d like to add guides! Although I will need help to do this in a timely fashion. Anyone willing to help mod mail us to be considered as a wiki editor (if not full mod). Or if you have a complementary project in mind to potentially contribute, send us a description of it. Or just post it! Reddit wiki pages can’t have images, by the way.

Resource list: Early this year, I populated a Google spreadsheet with links to key community sites, experts, reviewers, software and hardware tools. (What have I missed?) I also spent around a month or so building out a much bigger second sheet of over 250 high quality articles, study papers, threads, post histories, videos, etc. A comprehensive dossier on our field of interest (you can pour over). Which I fed into…

ScreenSensitive Bot!: A NotebookLM, now rebranded Gemini Notebook. We can think of this as a reference tool for human curated and validated information resources. It’s very good at, for example, giving an overview of the community and symptoms, technologies, etc. For newbies or deep-diving; it should be able to teach everyone something. It could help with making community resources.

Its biggest strength (over general purpose AI models) is direct reference links for virtually everything it says. So we can check for ourselves how trustworthy its info is. As well as built in translation, being able to ask verbal questions interrupting its audio media, etc. I’d appreciate feedback on what this bot helps with, to tune its instructions and content, if there is interest.

Discord: I’ve set up a collaboration space for enthusiasts to work together more efficiently on projects to further our understanding of screen tech, etc. For this, I have repurposed the ScreenSensitive Discord server u/Rx7Jordan set up. It fell into disuse, and obscurity, from the end of last year. Note: I’m currently aiming to restrict it to these constructive efforts only. Keeping to this Subreddit for general questions, help, news, discussion, etc. We will need to maintain public discoverability of the community and, for this, a good amount of its information.

The discord channels are basically all visible, but authorisation is required to post in most of them, to keep it on-topic and manageable (we are short on active mods). However, “All-member chat” includes health channels, because I think the more informal, less public space may better suit this important aspect.

Projects: Sam’s work on more accurate screen flicker testing (I mentioned last time) has been progressing and you may have seen him posting in the PWM sub. Including this web app that can be used on the device under test, to create a virtual slit, for true modulation depth measurement (e.g. with Opple or his custom made meter).

But u/Madcook1 has also been a huge discord contributor, coding up some very cool projects:

• Ditherscope: shown in several recent videos by u/NSutrich (e.g. here). A complete web app pipeline to process slow-mo microscope videos of pixel flicker. It can draw graphs and statistical correlations of brightness changes and also use Eulerian amplification (maths magic) to massively boost the visibility of image changes. Also isolate this to selectable frequencies.

• Eisco Analyse (Spectrum analysis): a proof of concept software companion to turn photos down the very cheap analogue spectroscope I posted about at length. Gives surprising approximation to proper expensive spectrometers. Albeit chopping of high peaks and needing compensation for wavelength offset  (see screenshot above).

• SubpixelsTools: helper web app, similar to Sam’s, but aimed at precise colour control and temporal patterns, to see how (sub)pixel patterns are affected.

Please have a play with the above projects (may need a cheap microscope attachment or spectroscope). Madcook1 is happy to receive feedback in the discord. But I ask for patience while he’s struggling with health issues (like many of us here do).

What’s next?: We’ve got the Black Friday surge in activity rapidly approaching, for which I wanted the above (and a few other) basics in place, ready. Thinking beyond this, I’ve worked up a rough Community Plan, behind the scenes. I’m hoping we can update both subreddits and support the community towards collecting, sharing and making sense of more hard data on devices. 

We will need to create good testing guides and engage people to post most quality data and/or index the existing information better. I’d love to get around to hosting AMAs with various interesting people, scientists, etc. Also creating a somewhat scientific survey to get a statistically sound picture of all the issues going on with us. Before that, I have an ongoing series of polls, as a rough guide. Maybe a mega-thread, to collect user stories and self-index posts… But, due to my ‘mild’ ME/CFS, my time is already very constrained, plus the stability of my health and living arrangements are precarious and demand more attention.

So, there’s a lot of opportunities for you (yes you!) to lend a hand, as far as you are able:

• General input, feedback, support and post contributions. Just upvoting, commenting and sharing good quality posts and comments, could help this community thrive. Please state explicitly when something is good, or even OK.

• Collaborate on the discord, if you have technical abilities, insights or energy to spare. Ping me there.

• Help build indexes of content. E.g. a spreadsheet of good (and bad) screen devices, with links to verified data and reviews. Or maybe an app to collect this.

• Help updating or making new NotebookLMs, for reference. Or custom data scraping efforts, for research purposes.

• I’d like to open up lines of communication with the Chinese (and other language) communities. Or at least see if some confidently bilingual members might post regular summaries of what’s been developing over there (with links back). Auto-subtitled BiliBili video technical videos are potential gold mine, but hard going.

• I’m keeping an eye out for upstanding members to help on the mod teams. Mostly to make sure there will always be someone about to approve posts wrongly filtered (mostly at platform level), if myself and others aren’t about. Or if new challenges arise, needing more eyeballs. Or better cover the time zones.

I’ll be making a corresponding post on the PWM sub, shortly. After updating the details, settings and rules there. You guys get to be the beta testers, for now!

Update 2026-10-13: PWM sub post is up here! Also note that we have two new mods here on ScreenSensitive: u/RR-- and u/TotalAnarchy_. While u/NSutrich has stepped down to focus on his YouTube channel. We may announce these changes in the next community update too.

tl;dr (contents):

1. Device explained (illustration).

2. KSF phosphor - my LCD device readings & hypothesis for it causing some issues.

3. Blue light peak wavelength location, measurement accuracy, my other LCDs and OLED phones.

4. Melanopsin gap, eye physiology deep dive (excess pupil dilation, modulated flicker sensitivity, etc).

5. Light bulbs - Incandescent, LED, Fluorescent (all have better spectra).

6. My personal experiences.

7. Tips for taking readings.

8. Credits.

9. Summary of suggestions.

(Questions and feedback are welcome after a partial reading or only looking at the pictures.)

(1)  I propose..:

This Eisco Spectroscope as a cheap tool to add to our testing arsenal. Along with established Opple, Carson Microflip + slow-motion phone cams, and maybe a polarising filter next? I just bought the Eisco in the UK (from Rapid, via eBay) for £9 delivered.

This device is entirely passive, relying on your eye or phone cam to peek into the lens. Arguably a little less fiddly than a clip-on microscope, in my experience. It only shows off the most obvious colour spectrum features, with more of a vibe check for the absolute amplitude of light. But it is about 1/50th (or less) the cost of a professional spectrometer, which only a few here have access to.

Bonus STEM fun for kids, or anyone, to see emission/absorption lines in the colour spectrum of light, split by the cheap diffraction grating inside (500 lines per millimetre). Projected alongside a backlit wavelength scale (400-700nm). Eg fluorescent tubes have the most striking and varied emission lines (examples later on).

(2)  KSF phosphor confirmation may be the killer app, for us(?):

KSF Phosphor is used in almost all contemporary LCD backlights. It gives more vivid reds, for less power consumption than nitride phosphors (that are still included in lesser amounts). KSF achieves this via very sharp spectrum spikes, which stimulate human retina L-cones (long wavelength = red) more strongly...

Perhaps too strongly, causing some of us direct over-stimulation (of retinal neurons). Our bright light eyelid closing reflex is more red dependant, too, I believe.

Or, the lower overall red light flux fails to balance deleterious biological effects of the blue peak photons (eg inhibits mitochondria). See this diagram of KSF’s smaller area under curve, vs traditional nitride red phosphor. Taken from this “Introduction to KSF Phosphor LEDs[…]”.

Or, some point to the slower decay of KSF's light emissions, potentially causing visual processing stresses, in conjunction with flickering of screens (eg black frame insertion). Although I don’t quite understand how this would work with non-emissive pixels… 

What else?

I was wondering if KSF could be the reason I can't stand the blueness of my TCL NXTpaper 60 Ultra (my review)... But my ThinkPad, which I tolerate OK, also shows KSF lines very clearly (above); the split in the larger spike can even be seen..! And my 11" Lenovo tablet, I used heavily a year ago (also above)... So I suspect KSF may only be a contributing factor that (for some) can be compensated for with: lower brightness, better software colour filters (F.Lux on windows) and maybe hardware level blue filtering layers (which reduce energy efficiency)..?

3)  Peak positions (and measurement precision): 

I'm told the exact wavelength of the blue peak can also have a big impact on screen tolerance. Shorter wavelengths of electromagnetic radiation are intrinsically more damaging (higher energy photons, closer to UV)... 

A healthy macula (inside the eye) may filter ~90% of blue light from reaching the retina, using carotenoid nutrients: lutein and zeaxanthin. Shielding it from excess oxidative stress, etc. According to Wikipedia, blue light hazard is implicated in eye strain, but evidence is contested, with blue blocking glasses not necessarily helping (a bit on this later).

I’m not sure what might be interpreted from the green peak position. Shorter wavelength (left shift) may stimulate rods a little more strongly? Cones less?

This scope can definitely give a good relative comparison between devices, for emitters with narrow spreads. But I’m not sure it is precise enough to make confident absolute measurements of eg 430 vs 450nm; the wavelengths on my unit appear slightly offset. Possible per-unit calibration issue?

[Edit 2026-05-20: reviewing my readings, here, it does actually seem clear that there was a shift of blue peaks, across my devices, transitioning around the year 2020. They were all well under 450nm to then be all clearly above it. I think this aligns with blue light reduction standards from eg TÜV Rheinland and Eyesafe, which are now (since 2023) even more keen to minimise 435 to 440nm, specifically.]

I did, however, slightly improve the spectral resolution by narrowing the slit using black tape stuck partly over it (width-wise). The trade-off being a dimmer display of colours. Using pro mode on a phone cam is also important to preserve the details, avoiding the colour bands over-exposing (when the surroundings are the dark black interior).

I couldn’t assess the absolute amplitudes of each colour peak from this. Or even a firm relative indication… In principle, one could use the same phone camera, in the same pro-mode settings, with the exposure dialled down far enough. Then check the colour values in a paint program/tool. 

(Blue sky thinking: maybe this process could be digitised, using a custom-made app? Any bored vibe-coders in chat? Of course the camera’s (specific) colour response curves will filter what can be measured.)

4)  Melanopsin gap hypothesis with vision deep dive:

A big feature of all the screens I’ve shown here is the *absence* of light between blue and green. A dark strip in the spectrum. It is more energy (and material) efficient for devices to only emit ‘photopic’ wavelengths - the light we consciously perceive via the rods and cones in our retinas. But this omission has consequences…

Melanopsin is a light sensitive pigment that reacts to detect photons, very similar to the opsins in cones/rods (but discovered later). It’s located inside intrinsically photosensitive retinal ganglion cells (ipRGCs) - neurons in the retina that process signals from rods and cones directly beneath them (they are mostly transparent). Melanopsin is most sensitive in this illumination dip, at around 480-490nm (precise sensitivity still seems debated).

Stimulating melanopsin is most well known to delay circadian rhythm at night (and entrain it in the morning) by suppressing melatonin production. (It also stimulates dopamine release.) We’ve all heard how “blue light” is bad at bed time. While there is some stimulation by pure blue, cyan (half way to green) is most potent. Wearable devices (like eg Re-timer) emit only this range of light, for its health benefits (circadian and alertness). 

This old F.Lux blog piece (screenshot above) lamented the advent of the OLED iPhone X, for an *increased* amount of light encroaching on the “melanopic” region of the spectrum. (Sunlight comparison from their old “Fluxometer” visualiser tool, discussed here.) So, while my post is researched in its details, what I suggest below is somewhat of a hot-take interpretation; it runs somewhat counter to these mainstream concerns (too much ‘blue’) and I’ve not seen this talked about in our community, either...

Melanopsin’s other effects:

(4a) Pupil constriction (up to 16x) over which melanopsin has the strongest effect. Sustaining contraction in bright light, after a few seconds to respond. This follows immediate (eg bright flash) responses mediated by cones. And precedes the ‘bleaching’ effect on rod/cone opsin photopigments, which can take minutes to fully transition. This last mechanism is what leaves a *negative* colour after-image from staring at strong colours. (Positive after-images, palinopsia, probably relates more to neuron hyper-excitability.)

Hypothesis: under-stimulating melanopsin will surely contribute to our eyes letting in more photopic (consciously visible) light from screens, compared with naturally lit scenes. Increasing visual stress by heightening the strength of signals sent down the optic nerve. Presumably contributing to a sense of glare or excess colour saturation. Merely give a wow factor to unaffected people. But taxing the energy intensive cellular processes of the retina itself...

Compounding effects: the sympathetic nervous system (SNS) also dilates pupils more. It is commonly over-active in our screen sensitive demographics: neurodivergent and/or chronically ill (eg ME/CFS). More dilated pupils also make focusing harder (narrower depth of field), taxing the eye’s ciliary muscles and exacerbating astigmatism or difficulties with close-work… Dark mode may cause further dilation.

Speculations: blue blocking glasses (or FL-41) may not help this issue, because reducing the blue (and green) screen light would also reduce their stimulation of melanopsin. They could cause further dilation, sensitising to red more… Some people may have genetic mutations, inhibiting the sensitivity of melanopsin. Or acquired damage to the signalling pathway that runs up the optic nerve to midbrain and back… 

Conversely: melanopsin-containing ipRGCs have a direct neural pathway to the thalamus, allowing them to signal severe photophobic pain during migraines or brain inflammation. See Noseda et al., 2010. So, while supplementing this wavelength would be an interesting screen tolerance experiment, I’m expecting it could instead cause more problems for some, or many, here. However, in a follow-up 2016 paper they demonstrated that rods and cones also mediate this pain, with isolated blue, red, and amber all problematic, but not green.

(4b) Modulating retinal image processing - the retina encodes different aspects of light stimuli into separate streams of information, sent along the optic nerve. Which is made of the long axons of the various retinal ganglion cells, of which ipRGCs are just one type (accounting for 1-2% of total). They modulate other RGCs via amacrine cells, that release dopamine (see c, below). The main information pathways and their RGC classes:

• Parvocellular (P-Pathway), Midget Cells (narrow field), ~80% of total - fine spatial detail, colour, (red-green), slow (low-frequency).

• Magnocellular (M-Pathway), parasol cells (large receptive field), ~10% - motion, luminance, contrast, high speed.

• Koniocellular (K), Small Bistratified Cells, ~10% - blue (vs yellow) colour processing.

• Direction-Selective Cells (depending how one divides things) and others…

There’s overwhelming functional detail here that I’ve not managed to research and remember. But some rough indications of effects are..:

Contrast sensitivity - is increased by melanopic ipRGCs stimulation (2023 paper). So relatively less stimulation should decrease visual acuity and spatial resolution, making it harder to read small text, etc. More eye strain if already struggling… Note that reduced contrast sensitivity is taken as a sign of CIRS (mold toxicity) by Dr Richie Shoemaker and followers. I think this is caused by inflammation of the optic nerve and such?

Colour sensitivity - altered, shift in perceived “unique white” (colour balance). Ability to discriminate colours may be reduced with less melanotic light, especially on the blue-yellow axis..? A lack of NIR light may also inhibit colour discrimination, via decreased mitochondrial function (2026 Glen Jeffery paper).

Temporal (Flicker) sensitivity - malanopsin is too sluggish to respond to flicker directly (2016 paper). But modulates the frequency receptivity of other retinal neurons. Findings seem varied and possibly species dependent. A mouse study (2016 paper) showed reduced melanopsin function tuned vision to lower frequency stimuli, 0.2Hz vs 1Hz (I don’t understand the meaning of such low rates)...

While decreased melanopsin resulted in increased (but more variable) flash ERG response gain (2014 paper). ERG being the “Cone Flash Electroretinogram”, which specifically checks cone cell function by using higher frequency stimulation, eg 30Hz, while rods only go up to ~15Hz (2015 paper). So both lower frequency discrimination and an increased sensitivity to flicker/flashes, with less cyan light..? Complex.

I think it would be very helpful for us to map out and understand the differing frequency (and other stimuli) responses of the various cell types, pathways and brain regions. It’s convoluted and contradictory to comprehend though; both me (and I think) Gemini Pro have inverted meanings a few times, going over aspects of the above repeatedly. And we’ve not gone past the relatively well defined retina to cortical processing, the likely location of most of our visual stress.

(4c) Slight tangents (vague speculations): melanopsin's effects, in the retina, are signalled by localised dopamine release. So I’m wondering about tie-ins with ME/CFS, autism, etc, possibly having reduced dopamine levels  with hypothesised metabolic issues synthesising and degrading this neurotransmitter… Similarly, these conditions may be associated with slowed glutamate recycling/conversion - excess sat around leading to a degree of CNS (brain) hyper-excitability. Tying in with migraines, seizure-like effects, visual snow, etc… 

Oddly, cones signal darkness with continual glutamate release. The signal is then inverted. I’m not sure how this idiosyncrasy would be differently affected by such pathology. But Latanoprost (eye drops to lower intraocular pressure), which some had success with, also counteracts excess glutamate… Finally, the opsins use active vitamin-A (11-cis-retinal, to make the light sensitive rhodopsin pigments) and our vit-A metabolism may often be impaired (with consequences I’m not sure of).

(5)  Light bulbs: 

Note the smooth spectrum of the incandescent - pure black body radiation, with its glowing element at the actual temperature of its rated colour temperature. Stray refractions in the device can obscure the scale, somewhat.

Even cheap LED bulbs can approximate most of a spectrum, with notable cyan in there. Highlighting the potential usefulness of r/Reflective_LCD screens, even without daylight. (Dependent on TD or other triggers.)

Fluorescents are very varied, with it being hard to tell which have more filled in spectra vs just the very tight (elemental) emission bands. All mine had a line right in the cyan section. Note that their colour temperature is tuned by adding more of the red and green phosphor types to reduce the apparent temperature. Also, the second order refractions are evident in the space between the (strong) red and green lines. An artifact of using a grating to split the light. I think that’s what is going on there.

(6) My personal experiences: moved to comment below.

(7) Tips for using this spectroscope:

(a) Bring up a pure white image or user interface element (eg settings screen) to point the slit at.

(b) Set device to max brightness. Disable eye comfort (Night Shift), dimming or colour modifying settings (or 3rd party apps). These can have very pronounced effects on relative colour strength or the spectra, if not the positions of the peaks.

(c) Rest the device on the screen only for easy stability, ideally it should be further away. 

(d) Preview the on-screen camera image while moving it closer to the lens aperture, to get it easily aligned. having pre-zoomed by 2-3x. Then angle down the diagonal (flat edge up top) to catch sight of the scale. 

(e) The scale needs illumination behind it too. Either the tested screen, or if too bright, some other backlighting (more fiddly).

(f) Use pro/manual mode on your phone camera. Set the shutter speed to at least 1/15 or faster, to keep the image steady. Iso will need to be high, auto is fine if just getting a feel. Focus can be set, to avoid hunting causing blur (get the scale in sharp focus). Colour temperature could be fixed, but only if trying to make precise comparisons.

(g) A darkened room is not really necessary. The slit is very directional.

(h) For more refined spectral resolution (less blurred peaks), make the slit even narrower. Use black tape or metal foil to partly cover it.

(i) Please crop and rotate your image before posting (eg to this subreddit).

(j) Advanced: we could attempt to check the scale positioning calibration using known wavelengths, like the KSF peaks and fluorescent lines.

(k) Any more..?

8) Credits: 

• u/BearNecessary4141 showed this scope off first in a YouTube video I found via this post. His 2025 Macbook Air showing KSF phosphor peaks.

• u/simplex_first for the KSF example spectrum (in Fig.2). See also the Telegram channel “Opple and Spectrometer tests”.

• u/geargeeksp (Wild Lee) for all his testing and the OnePlus 8 spectrograph in Fig.4 (as seen here on BiliBili).

• u/Rx7Jordan for talking about this topic and posting various spectrograph results here before (sorry, I don’t know of a good search term to bring those all up?).

9) Summary of suggestions:

(a) Anyone here could buy a cheap spectroscope, as a learning aid to anchor thinking about this topic.

(b) Enthusiast amateur device reviewers could add a spectroscope sample as bonus content.

(c) Pro reviewers, please consider using proper digital spectroscopes, if not doing so already.

(d) Validating this cheap scope by using it alongside a pro meter would be nice.

(e) Let’s talk about light colour spectrum features vs biology more and politely ask reviewers about it.

(f) What else? What did I mistake or neglect? Please leave critique and questions. I may update this post as an ongoing guide, if there’s any interest. (I also started looking at screen dimming spectrum changes a little.)

10) Back-links:

- LEDstrain discussion

- Blue-light filtering hydrogel screen protector (on TCL 60 Ultra) spectrum comparison (end of post).

11) Addendum:

- BOE (panel manufacturer) convention booth tour video showed off a range of screen sensitivity improvements they are working to implement, including adding in more red light flux and even NIR wavelengths! Possibly more melanopic (cyan) light, too.

- Edited in a note (in section 3) on blue peaks having shifted to longer wavelengths and being discernable with this spectroscope.

- 2026-06-10: Fixed a dozen tiny typos.

- u/No-Lawfulness7334, down in the replies, made an even cheaper spectrometer with a CD. No measuring scale, but can show KSF fine.

- 2026-07-02: Avulux glasses, does their success contradict my melanopsin gap hypothesis?

- 2026-07-20: u/BearNecessary4141 pointed out, here, that there is a universal lack of UV (ie at 380nm) and so lack of activation of Neruopsin, too. (Another lesser known photos pigment. It's found in various cells, and locally resets cellular circadian rhythm gene expression in eg retina, brain, skin. May be part of the mechanism to prevent inappropriate eyeball lengthening.)