Difference between revisions of Chromatic Aberration

Jump to navigation Jump to search
No edit summary
(7 intermediate revisions by 5 users not shown)
Line 1: Line 1:
Chromatic aberration is probably most easily understood as a prism effect.  When light shines through a prism, you see that different colors of light bend differently and create a rainbow effect.  When light shines through any lens, including glasses and the natural lens of your eye, the same occurs to a lesser degree.  The effect of this is that the [[Focal Length]] of the lens is not exactly the same for all colors of light.   
Chromatic aberration is probably most easily understood as a prism effect.  When light shines through a prism, you see that different colors of light bend (undergo [[Refraction]]) differently and create a rainbow effect.  When light shines through any lens, including glasses and the natural lens of your eye, the same occurs to a lesser degree.  The effect of this is that the [[Focal Length]] of the lens is not exactly the same for all colors of light.   


= Duochrome test =
[[File:Chromatic aberration lens diagram.svg|Chromatic aberration lens diagram]]
 
== Duochrome test ==
{| class="wikitable"
{| class="wikitable"
|-  
|-  
Line 11: Line 13:
|}
|}


The chromatic aberration expected during a normal eye exam is about a half diopter difference between red and green.  This can be a handy test to dial in a final prescription by looking at text on red and green backgrounds and seeing which is clearer.  For a [[Full Prescription]], if the green side is clearer, a quarter diopter of sphere is added, if the red side is clearer, a quarter diopter is removed.  If the optometrist is trying to introduce a small amount of [[Myopic defocus]] he/she wants the red side clear.
The chromatic aberration expected during a normal eye exam is about a half diopter difference between red and green.  This can be a handy test to dial in a final prescription by looking at text on red and green backgrounds and seeing which is clearer.   
 
<youtube>WP6eeoyB9go</youtube>
 
== External Sources ==
* [[Wikipedia:Chromatic aberration]]
* [[Wikipedia:Duochrome test]]
 
== Lens Material ==
Different materials have different [https://en.wikipedia.org/wiki/Abbe_number Abbe numbers]. Materials with higher values are better, since they tend to have less chromatic aberration.
 
Here are some typical values:<ref>https://www.allentownoptical.com/abbe-value-interpretation/</ref>
 
{| class="wikitable sortable"
!Material
!Index
!Abbe Value
|-
|Crown Glass
|1.523
|59
|-
|High Index Glass
|1.60
|42
|-
|High Index Glass
|1.70
|39
|-
|Plastic CR-39
|1.49
|58
|-
|Mid Index Plastic
|1.54
|47
|-
|Mid Index Plastic
|1.56
|36
|-
|High Index Plastic
|1.60
|36
|-
|High Index Plastic
|1.66
|32
|-
|Trivex
|1.53
|43
|-
|Polycarbonate
|1.58
|30
|-
|MR-174
|1.74
|32
|}
 
==References==
{{reflist}}


= External Sources =
[[Category:Articles]]
* https://en.wikipedia.org/wiki/Chromatic_aberration
* https://en.wikipedia.org/wiki/Duochrome_test

Revision as of 00:23, 29 August 2021

Chromatic aberration is probably most easily understood as a prism effect. When light shines through a prism, you see that different colors of light bend (undergo Refraction) differently and create a rainbow effect. When light shines through any lens, including glasses and the natural lens of your eye, the same occurs to a lesser degree. The effect of this is that the Focal Length of the lens is not exactly the same for all colors of light.

Chromatic aberration lens diagram

Duochrome test

KH HK
EPO OPE

The chromatic aberration expected during a normal eye exam is about a half diopter difference between red and green. This can be a handy test to dial in a final prescription by looking at text on red and green backgrounds and seeing which is clearer.

External Sources

Lens Material

Different materials have different Abbe numbers. Materials with higher values are better, since they tend to have less chromatic aberration.

Here are some typical values:[1]

Material Index Abbe Value
Crown Glass 1.523 59
High Index Glass 1.60 42
High Index Glass 1.70 39
Plastic CR-39 1.49 58
Mid Index Plastic 1.54 47
Mid Index Plastic 1.56 36
High Index Plastic 1.60 36
High Index Plastic 1.66 32
Trivex 1.53 43
Polycarbonate 1.58 30
MR-174 1.74 32

References