How do you ensure the quality and performance of a low-light scope?
Are there any other factors about light transmission that you should know about? More importantly, are there any misconceptions that you are better off knowing?
These are questions I used to ask myself about rifle scope light transmission. If you are in a similar position, it may be time to read through this article.
I’m here to break down light transmission to what it really just is: BRIGHTNESS.
Contents
Let’s Talk About Brightness
At first, the concept of low-light performance sounded quite technical to me.
But I learned it simply refers to how well and bright you can SEE in a low-light environment.
There are FIVE ESSENTIALS for a riflescope to perform well under such conditions:
- Large exit pupil to maximize your eye’s light processing ability
- Large front objective compared to other parts to absorb more light
- Ample size of the main tube to facilitate passage of light
- Good light transmission to ensure better imaging
- Allowance of lens coating to minimize reflection
It’s sacred for hunters and tactical shooters to equip their rifles with scopes of low-light performance.
Without this feature, how else would you expect a hunt to go at dusk or dawn?
Great! Now that’s out of the way… why is this important again?
Comparing Light Transmission Among Rifle Scopes
Believe it or not, light transmission is more complex than the five essentials for scopes. There’s a different kind of approach to assessing your rifle scopes.
In truth, MORE light transmission DOES NOT necessarily translate to better light transmission.
What may be more important is HOW the riflescope manages specific light waves transmitted onto your eye.
This is what supposedly gives you BETTER contrast and resolution for low light-gathering ability!
Trust me; I was confused too. I understand how this may feel counterintuitive to what you’ve known so far.
Let’s go ahead and finally address these questions to set the record straight once and for all.
The Bigger Lenses, the Better?
Remember these two among the five essentials?
- Large exit pupil
- Large front objective
Would you believe me if I tell you that this isn’t always going to be required?
Large objective lenses indeed need more light passing through a rifle scope.
What scope manufacturers don’t tell you is that low-light rifle scopes’ performance also depends on the MAGNIFICATION.
Let’s Clarify the “Magnification” Part
If the magnification is low enough, then a small objective lens would also be as bright as a larger one.
This is because the exit pupil is EQUAL to the objective diameter divided by the magnification.
The logic shouldn’t feel all that different since this is also how CAMERA LENS work!
Reflected light passing through a SMALL HOLE results in a SHARPER image.
A SHARPER and clear image can result in a more defined image DESPITE low light conditions. It lets you see more detail!
Keeping your resolution sharp is as important as the inherent scope brightness of the optics.
Yes, larger objective lenses allow more light into the riflescope for added brightness. However, bigger DOES NOT always mean better. Balance your features!
To learn the difference between magnification and distance, check out this guide!
What Does the Main Tube Have to Do with It?
Nothing much, really.
The size of the main tubes only matters in relation to the sizes of your rifle scope’s optics.
- The LARGER the main tube diameter, the MORE ROOM for knob adjustments.
- The LARGER the main tube diameter, the larger the lenses that it can CARRY.
Remember that larger lenses are also just inherently sharper than smaller ones, meaning that the light transmission is assumed to be better!
At the end of the day, how much light exits the eyepiece depends on the magnification of your lenses and NOT the size of the main tube.
Learn more about how to adjust your scope here!
Do Lens Coatings Improve Light Transmission?
Yes. Riflescope brightness DOES improve with the use of anti-reflection coatings.
Applying anti-reflection or anti-reflective coatings on your lenses can easily DOUBLE THE SCOPE BRIGHTNESS.
Anti-reflection coating does this without all the necessary bulkiness and weight of lenses or accessories… with better specifications!
Anti-reflection coatings achieve this visual marvel through wave phase cancellation.
To summarize this science to you:
Raw glass loses 4% of the light that hits and exits through it. This is caused by the air-to-glass interaction that is translated through reflection.
The coatings of some earth minerals reduce reflection loss.
Why are these important?
Visualize your riflescope right now… You should notice that it has