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Comment by mrob | Hacker News Reader

>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

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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.

Deal with it for a few weeks, your brain will likely adapt.

This really bothered me many years ago, and I tried CR-39 and even glass, just for fun. I was never that happy with the results. I could always distract myself with chromatic aberration, and I think I eventually decided not to care anymore.

But right now, I have high index lenses and am reading HN with Dark Reader, and even if I use the maximum strength of my glasses (progressive bifocals), I can't really see any chromatic aberration.

I'm not sure if I should be happy or worried.

For those with stronger prescriptions who want higher index lenses to reduce thickness (and weight), look at http://opticampus.opti.vision/tools/materials.php and/or talk to your optician about available materials. (Personally, I've settled on MR-8 for my last couple pairs of computer glasses.)

I thought I got used to the color fringes in my glasses, but the real problem is that they actually reduce image clarity away from the center of the lenses. If you look e.g. at white text on a dark background from an angle, the chromatic aberration blurs (the color components of) the letters together. You can't really see clearly by moving the eyes to the edge of the FoV of your glasses; you have to turn your head instead.

This is directly contradicting the main purpose of glasses: to see clearly. So it's actually somewhat less safe to e.g. drive with glasses that have major chromatic aberration. No idea why optometrists brush it off as a minor glitch.

I can’t speak to glasses, but limiting chromatic aberration in the binocular world does seem to involve coatings (at least as Swarovski, Leica, Zeiss present it).

If you cut some wavelengths, you won't get their contribution to the distortions ;)

You can’t eliminate chromatic aberration with coatings, it’s a physical property of how the lens interacts with light. The only way to fix it is to adjust your lens types or materials. Zeiss’ current marketing seems to agree https://www.zeiss.com/consumer-products/us/nature-observatio...

Coatings are still very useful to reduce other lens artefacts though.

Can you link to something to buy?

I don't think anybody makes achromatic glasses lenses because they would be too thick and heavy.

AFAIK, every optician sells PADC (e.g. CR-39) lenses.

TIL. Thank you.

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