Is my vision that bad? No, it's just a bug in Apple's Calculator

One of my favourite unreported MacOS issues comes from how, at some point, they changed the appearance of the window close button to be a particular shade of red with a tiny little X in the center. And if you happen to be using a particular kind of screen and possibly wearing glasses, that little X kind of wanders around in the button, appearing just slightly off center in a maddening way. Made only more maddening by the glasses component: https://www.robbert.org/2014/10/the-off-center-close-button/.

That post points out it’s probably just subpixel stuff causing the issue, but I think my thick, cheap glasses at the time were adding a layer of chromatic aberration to something that was already visually confusing.

I assume it’s kind of gone away at this point with all the high DPI screens these days. But I remember thinking at the time, if there was a public bug tracker, that issue would be a fun one.

>More expensive lenses have a coating to compensate for this chromatic aberration.

You can't compensate for chromatic aberration with a coating. You need a compound lens made from multiple elements each with a different dispersion, e.g.:

https://en.wikipedia.org/wiki/Achromatic_lens

More expensive glasses lenses usually have worse chromatic aberration than cheap ones. The cheapest material for glasses lenses (PADC, often called by the brand name CR-39) has one of the best Abbe numbers (measure of dispersion).

https://en.wikipedia.org/wiki/CR-39

https://en.wikipedia.org/wiki/Abbe_number

I can confirm this. I had annoyingly bad chromatic aberration with my previous glasses. I specifically asked for CR-39 lenses for my next set of glasses and now it's barely noticeable at all.

I would recommend this to any programmer who uses high-contrast syntax highlighting. To me, it felt fatiguing every time I noticed differently colored words scrolling slight further than other words on a terminal screen on the same line.

One thing to keep in mind is that CR-39 is not impact resistant. They will shatter and can do horrible things to your eyes when they do. Kids should always be put in impact resistant lenses.

If you’re a desk jockey, or impact resistance is not a concern, CR-39 will give the least aberration with the exception of crown glass.

The hidden hack here if you need/want impact resistance is to ask for Trivex lenses. Same impact resistance as polycarbonate but much better ABBE value. It’s often overlooked because it costs a little more than polycarbonate and most people don’t complain about the distortion.

Also, anecdotally, you get what you pay for with progressive lenses. I have a cheap lens in my sunglasses and a higher end lens in my daily drivers and I can easily tell the difference.

> It’s often overlooked because it costs a little more than polycarbonate and most people don’t complain about the distortion.

I just started wearing glasses. I asked about fringing and they had brushed my concerns off as me being new to glasses.