macsforme That’s interesting and thanks for sharing! How does your specific capture card work? What resolution and FPS does it support? I’ve seen some recordings here that seem to capture frame differences down to a single pixel. But can it detect more subtle flickering – the kind that might occur within a single refresh cycle?
Also, what’s the highest frame rate it can handle? Can it run in a super-slow mode, like a high-speed camera, to catch flicker that happens between refreshes?
From what I’ve researched, the panel refresh and rendering pipeline are way more complex than a simple "1 FPS from software = 1 Hz from display" scenario. The deeper I look, the more layers there seem to be. I’m curious about what else might be flickering, moving, or changing that affects the eyes – even when dithering is disabled and backlight flicker is addressed. Is it something a capture card can reveal, or is a high-speed external camera the only option? Or maybe it's something that can't be captured at all?
Personally, I don’t notice much difference with dithering on or off on the machine I use daily. But I ran a few tests from first principles. For example, I tried a basic full-screen redraw test – similar to how simple USB capture cards operate (e.g. taking a full-screen screenshot 30 times per second and streaming it). That caused significant strain. So I slowed things down and ran another test: changing full-screen images (JPG, PNG, BMP) once per second, using no scaling, no smoothing, and pixelated rendering. Even then, every time the image changed, my eyes seemed to shift or react. I tried different render engines, browsers, etc – same result. But if I load an image once and scroll around like crazy, no issue at all.
Another test: a completely white image being redrawn onto a white background. No visible change, yet every time it’s redrawn, my eyes feel a shift. Same thing happens when quickly switching images using the Windows “Photos” app. So I’m wondering: what exactly causes this? Is it rendering? Compositing? Even when rendering white-on-white, there’s a subtle strain or shift – like the eyes lose focus briefly. Is it backlight-related? Panel response? Microflicker from the OS? Subpixel transitions? Or something like CRT-style flicker?
These are just a few examples, but it raises a bigger question: what is really going on during rendering? And how could one capture that "something" that’s happening during redraws – especially when the pixels technically haven't changed? Why are some things totally fine (like static images, fast scrolling, most apps), while others – like HTML5 games, apps using <canvas>, or some Vue.js interfaces, most remoting softwares – cause visible discomfort or strain (to me)? Of course there most probably are multiple elements that flicker/change/move and most probably they are very subtle. But if there is some kind of super small change, in theory it should be possible to detect that difference with the right equipment.
I’d love to hear from others who’ve dug deep into this. Any insight would be much appreciated.
Thanks a gain for sharing all the research done with your capture cards!