Fun with Astigmatism: DuoChrome Walkaway

DuoChrome tests indicate whether you’re overcorrected or undercorrected: if the black circles on the green side look clearer you’ve got too much minus correction, and if the black circles on the red side look clearer you’ve got too much plus (not enough minus). And if they look the same you’ve got the correct correction for the distance.

For me the red side looks better from across the dark room, which makes sense since I have some astigmatism that I’m trying to get rid of. I can see the circles on the red great and the green glitches out with naked eyes. Now, here’s where it gets fun (or perverse), if you start from far away, where you can’t really see the circles clearly or they’re turning into & or something, start walking forward to the screen until you get to the point where you can see all four double circles clearly with no defects. Close your eyes and open them a couple of times and make sure the circles all still look fine. Then keep staring at the circles and trace them with your eyes (like you’re zooming around a race track) and SLOWLY walk back and see if you can keep all 4 double circles from glitching out. I can get to the end of the room and keep the image pristine, and even blink my eyes a few times and keep them nice, much better than I can keep them from putting them up on the screen and then walking far away and approaching them. Other astigmatism test images look good for me from that distance >8m / 26 feet if I can hold that mental state and put them up on the screen, but I can’t enter that state from >6m away.

I guess people probably have similar issues with active focus for myopia? You might be able to achieve AF, and then push the distance considerably further than the distance from which you could enter AF?