If you have bought a red dot sight, you might already learn that red dot sights may fail sometimes due to extreme environments or some accidents, therefore if both iron sight and red dot sight are used while shooting, it will be more precise and also increase the speed of target acquisition. So the question is: What is absolute co-witness height? What does lower 1/3 co-witness mean? Which one to choose?
What does it mean to lower 1/3 co-witness height and absolute co-witness height?
First of all, absolute co-witness and lower 1/3 co-witness are just different installation methods. The height of your red dot sight (the amount of iron sight that occupies the sight picture of your red dot) is the biggest difference between them, so in fact there is nothing good or bad about them, just choose a proper one according to your shooting preferences.
There are 3 popular center heights, as picture 0 shows, the absolute co-witness height is 36mm (1.4 inches); the lower 1/3 co-witness height is 40.4mm (1.6 inches); the other one is 38.1mm(1.5 inches).
If you still feel confused, picture 1 will show you what absolute co-witness and lower 1/3 co-witness look like, thus more clear for you to understand. If you mount the red dot sight in the way that the center dot coincides with the iron sight in the middle, this is called absolute co-witness or 100% co-witness. If you mount the red dot sight higher than the iron sight, and the iron sight appears in the lower 1/3 of the optic window, it is called Lower 1/3 co-witness. You need to change your line of sight to make the red dot align with the iron sights.
Pros and cons of absolute co-witness and lower 1/3 co-witness
Using Absolute co-witness, the red dot is always aligned with an iron sight so you can react faster and more accurately when the target appears in your field of view, but the iron sight will block part of the field of view.
Using Lower 1/3 co-witness can provide a wider field of view and less interference, but you need to change the line of sight when you need both red dot sight and iron sight.
Summary
| Absolute co-witness | Lower 1/3 co-witness |
| Pros:
1. Shooters can react faster 2. More accurate Cons: The iron sight will block part of the field of view |
Pros:
1. Wider field of view 2. Less interference Cons： You need to change the line of sight to coincide the red dot with the iron sight |
Therefore, the best advice is to try them both, then make a choice between absolute co-witness and lower 1/3 co-witness according to your personal tastes and habits.
Check the most cost-effective VictOptics red dot sights here to set up for your co-witness settings.