Glasses and problems with chromatic aberration

[woody123]

TL;DR Summary

How can i reduce chromatic aberration?

Hello, i wear glasses (i have 2 pairs) ones are 1.60 esseilor (-4.50 and -4.75) cylinder 0,25 both and new ones that i got yesterday Trivex perfalit 1.53 (-5.00 and -4.75) cylinder 0,25 both.(+ antireflex both) And the problem with first ones was from center i see ok but when i look at the sides there is a lot of chromatic aberration same with new trivex, so i googled some stuff and figured that ones before have 36 abbe and trivex has 43 (as higher abbe value should reduce abberation) but i see the same thing, nothing changed. should i go with cr 39 that have 59 abbe or something higher? because i really want this stuff to not be visible. btw i have -2.5 (both) glasses also that have cr39 but there i can't see any aberration but the dioptrie there is half as on my current ones. Also these optics here have no idea what chromatic aberration is (weird).
Thank you for any help
Ps english is not my prime language so if you need any clarification ill try to explain better.

 

[sophiecentaur]

ED (low dispersion) glass is used in lens design but I have not heard of its use in specs. CA can be corrected (improved) using a doublet with two glass elements with different RI. But the requirements for specs are quite demanding. A very wide field of vision is needed and glass is not popular these days as it is so heavy compared with plastic. Have you tried googling CA in eye glasses?

 

[woody123]

i did but as i have figured out i need to have high abbe as possible, but maybe i need cr 39 glass because it has highest abbe value and that means less chromatic aberration. What about glass, does it have abbe value and chromatic aberration?

 

[sophiecentaur]

What about glass, does it have abbe value and chromatic aberration?

Of course it does. It's a general measure for any transparent substance, I think. From what I can find on Wiki and elsewhere, crown glass has an abbe number of about 60. This link tells us that ED glass has an abbe number of around 90. That would cost a lot for a pair of specs and there may be disadvantages in the form of extra weight and less strength.

Also these optics here have no idea what chromatic aberration is (weird).

I think you mean Opticians here. It's not too surprising if these guys are basically just salespeople. I would suggest you did some searching with terms like "ED glass in spectacles". If you have a prescription then you can have specs made up on line and there are bound to be companies that will supply anything that can be actually made. It may be very expensive though so you would need to decide on how worth while it would be for you to have improved CA.

 

[DannoXYZ]

With amount of correction dioptre you need, lens need to be thick with short focal length, which increases CA.

It is difficult to have low CA with single material. As mentioned an achromatic doublet lens with two materials and opposing focal-lengths are needed to cancel CA. Since resultant CA is based upon this function (abbe=v):

f1•v1+f2•v2=0

having one lens in doublet with opposite focal-length allows you to cancel abbe of one lens with other's -abbe. In order to reach final non-zero focal-length desired, one lens needs to be stronger than other. So abbe of each lens should be selected based upon ratios of focal lengths for best cancellation.

Not sure if this can easily be done for specs with amount of glass required. Perhaps two different types of polycarbonates can be used. It's definitely a small market as most specs don't have as much correction as yours, so there's little demand.

 

[woody123]

So for next glasses i should go for crown glass or cr 39 (high abbe) ?i know they will be thicker but i just want this to be minimised as much as possible.

 

[gmax137]

... -5.00 and -4.75 ... And the problem with first ones was from center i see ok but when i look at the sides there is a lot of chromatic aberration ... because i really want this stuff to not be visible.

It's definitely a small market as most specs don't have as much correction as yours

I have a much (much!) stronger script -- the effect is very noticeable with the last few sets of lenses. While the new materials result in thinner, lighter lenses, the aberration effect is much more pronounced. If I turn my head while looking at blue LEDs (such as the "ON" lights on things these days) the LED appears to move by inches relative to the stuff in the background. It was annoying at first but mostly I am accustomed to it now.

 

[DannoXYZ]

So for next glasses i should go for crown glass or cr 39 (high abbe) ?i know they will be thicker but i just want this to be minimised as much as possible.

Sure, most glass has less CA than plastics.

 

[woody123]

is there higher abbe value than cr 39 (58 abbe) that is meant for glasses?

 

[sophiecentaur]

is there higher abbe value than cr 39 (58 abbe) that is meant for glasses?

How much have you searched for an answer to this? I saw a glass with abbe value of 90, whilst scanning through a post. But a doublet would do the job better.

It was annoying at first but mostly I am accustomed to it now.

That attitude could save you a load of money! It's not quite the same thing but people who are new to varifocals can be unsettled by the bizarre geometry of what they see. I found that everything settled down after a day or two with a new pair.

 

[woody123]

well i have them for 4 years and still notice it every time, yeah it gets less annoying but still, i think i will try cr 39 on next ones. Thanx

 

[sophiecentaur]

well i have them for 4 years and still notice it every time, yeah it gets less annoying but still, i think i will try cr 39 on next ones. Thanx

That could be difficult. Spectacle lens manufacturers are conservatively minded and it could be very expensive to have a bespoke lens ground to an awkward prescription. Good luck with searching for one.

 

[woody123]

i payed 160 euro for trivex with antireflex. They are thicker but oh well.