The RPO 4.0 eyepiece is here, and it might just be the sweet spot night vision users have been waiting for. In this post, we’re breaking down the differences between the new RPO 4.0 eyepiece and its predecessors—RPO 3.0, RPO 2.0, and the military-spec Carson/Fujinon optics. Whether you’re running a monocular, dual-tube, or bridge setup, you’ll want to know what this upgrade offers.
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RPO Evolution Overview
- RPO 2.0: Loved for its long eye relief and minimal distortion. Downsides were durability and focusing issues in some applications.
- RPO 3.0: Introduced a threaded build and fixed those focusing issues. It was great—especially for dual tubes—but had a shorter eye relief and more lens flare.
- RPO 4.0: Brings back the clarity and comfort of the 2.0 eyepiece with the rugged 3.0-style threading.
We got our hands on the 4.0 and did a side-by-side test. Here’s what we found.
Test Setup: Monocular Comparisons
We used four monoculars, each featuring different optical builds:
- Monocular 1 – Mil-Spec Carson eyepiece + Fujinon objective
- Monocular 2 – RPO 2.0 eyepiece + RPO 3.0 objective
- Monocular 3 – RPO 3.0 eyepiece + RPO 3.0 objective
- Monocular 4 – RPO 4.0 eyepiece + RPO 3.0 objective
Each monocular had a similarly specced Elbit SLH tube for consistency.
Vignetting and Eye Relief
- RPO 3.0: Known for tight eye relief. If you move even slightly off-center, image quality drops.
- RPO 4.0: Improved significantly. Less vignetting and more forgiving head movement.
- RPO 2.0: Still the benchmark in comfort, but the 4.0 comes close.
- Mil-Spec: Very flat and consistent across the image, but heavier.
Lens Flare Comparison
We tested each optic by shining a Modlite OKW directly into the lens.
- Mil-Spec: Very little flare, but heavy and not as sharp at the edges.
- RPO 2.0: Low flare and wide field of view.
- RPO 3.0: More intense flare, more “blowout” in the center.
- RPO 4.0: Flare levels sit between 2.0 and 3.0—noticeable but not distracting.
Light Transmission Test
We ran all monoculars in a completely dark indoor setting to see how much ambient light each optic let through. The results?
- RPO 4.0: Edges out the 3.0 in clarity and brightness.
- RPO 2.0: Just behind the 4.0—still excellent.
- Mil-Spec: Performs well, but colors feel flatter.
- RPO 3.0: Slightly dimmer and more distortion on the edges.
Weight Comparison
Weight can make or break your setup, especially for dual tubes. Here’s what we measured:
| Optic Setup | Weight (g) |
|---|---|
| Mil-Spec | 126.87 |
| RPO 2.0 | 66.50 |
| RPO 3.0 | 59.39 |
| RPO 4.0 | 64.05 |
The RPO 4.0 gives you much of the performance of the 2.0 with the ruggedness of the 3.0—without sacrificing weight.
Final Verdict: Is RPO 4.0 Worth It?
If you’re building a new dual-tube setup or looking to upgrade your existing eyepieces, the RPO 4.0 is a compelling option. It brings back the comfort and clarity of the 2.0 while keeping the rugged feel and threaded interface of the 3.0.
✅ Better eye relief
✅ Less vignetting
✅ Improved durability
✅ Competitive weight
You can find the RPO 4.0 eyepiece here.
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