Lens Aberrations Explained

In case you ever wanted to add chromatic aberration to a perfect image, I made kromo:

https://github.com/yoonsikp/kromo

As a side note, isn't it ironic that games now resort to adding aberrations to make it seem more real?

About 15 years ago I participated in a study of wavefront lenses(I think it was by Zeiss). The glasses were single prescription and they were hands down the best glasses I've ever owned. Great vision and low chromatic aberation.

I've never seen the tech offered for single prescription lenses since then. I really wish they continued with the technology.

I've got a smartphone with a not so good camera. Some time ago I heard about an app that could take a picture of a template and then would calculate the distortions of your camera and fix those (with ML).

Does anyone know what app/research this is? I can't imagine why smartphone maker don't use this for their crappy camera's so they can still embed cheap camera's but enhance the picture quality.

My favorite site for explaining lens aberrations (unfortunately, it's currently under construction in a new URL) is here:

https://web.archive.org/web/20090204211139/http://toothwalke...

It's a fantastic resource.

Since the recent (2019) mathematical discovery allowing elimination of spherical aberration[1], I've wondered if lenses will either be simplified, or redesigned for better optical performance.

[1] https://arxiv.org/abs/1811.03792

Slightly topical: there's a steam game "Umurangi Generation" that aims to be a realistic photography simulator.

Wow, I have a lens with noticeable Focus Shift. I thought it was just some mechanical play in the mechanism, but Today I Learned it's a Thing.

I wear glasses and recently significantly increased the power on one of the lenses (weirdly, not in the other). I also got larger lenses (so distortion that happens in the corner is increased because the corner is farther from the midpoint than before).

The main issue with the new lenses which I noticed was chromatic aberration. Unfortunately my brain can’t fix this in post though it has gotten used to it a bit. Something that I suppose I already knew was that the lens material would affect how much of this distortion you would see. I thought different refractive indices would give different amounts of dispersion, though maybe I should not have thought that as lower indices would mean thicker lenses so more distance to disperse in which might cancel out the lower disposition. In the end it doesn’t matter what I thought, the Lens material does affect the dispersion.

The thing I was more surprised by was that dispersion wasn’t something that came up when making the choice of lens material. Thinking back though, perhaps the only qualities discussed were “thickness” and cost. I put thickness in quotes as maybe the weight was discussed too. I feel like dispersion is quite an important thing I care about and I wonder why it wasn’t discussed. Perhaps it is hard to explain to people (I guess all the material properties are hard to explain), or perhaps it is difficult if the lenses don’t necessarily get better in every way as cost goes up.

There are no glasses lenses which can correct for their chromatic aberration like camera lenses, presumably because they would be too thick and delicate.

In a more general sense, I’m surprised that there’s so little variety in optometrists (at least in the U.K.). Basically wherever you go you get the same precision of prescription and are then given the opportunity to buy some glasses. Some studies have shown that the accuracy of the prescription you get from the subjective refractometry exam can vary a lot between practices but there is no way to know if a practice will be good or bad. I’m also surprised that there is not really a way to get a more accurate or precise prescription than the standard, as I would think that if such a thing existed it would be able to find customers at least in larger population centres. Maybe it would be impossible to improve on the status quo because of the lack of economies of scale or because glasses won’t be in a consistent enough position or because the rich people who would be expected to pay floor the service opt for eye surgery instead.

This comment is so far mostly unrelated to the OP though so I will make another comment: I wish the article had mentioned some of the physics behind the different aberrations, for example the reason longitudinal aberration is hard to correct in post is that it os an effect where different colours are focused to different distances and it of hard to make a colour less out-of-focus to fix it. The reason a bokeh light circle is a certain shape is that that is the shape of the lens aperture (hence usually a circle or many-gon). The misshapen bokeh effects tend To come from light coming in at more acute angles and from those angles the lens is a different shape.

As someone who’s been photographing for a few decades now, it looks like the recent iterations of lenses from the big brands are basically “perfect.” 70s and 80s lenses had tradeoffs... with today’s lenses from Canon/Nikon/Sony, those made in the last 5 years or so, the optical quality after digital correction is so high that for any non-extreme form of photography they can be considered perfect. And that goes from lenses like Canon’s 35 1.4 ($1800) down to their 10-18 ($250). The gearheads can natter online but the returns here are now nearly fully diminished.