RPO lenses - worth the hype?


A new line of PVS-14 lenses made by Rochester Precision Optics (RPO) have been gaining popularity in recent months due to their reduced weight over standard PVS-14 lens assemblies. We acquired a set for Testing and Evaluation and to determine viability as a future offering. Here are our findings:

Setup

The test above was conducted as follows:

Camera: Sony A7S3 with 16-35 Sony G-Master F/2.8 lens mounted on Peak Designs aluminum tripod; PVS-14 DSLR direct lens adapter
Settings: 1/50s shutter; F/2.8, manual white balance, 24fps, S-Log3 colour profile, manually focused
Night Vision Device: CH/PVS-14 Pro with objective retaining ring removed to facilitate swapping of objective and ocular lenses
Image tube: Photonis Echo MX-11769 white phosphor intensifier (same tube/device used for both shots)

A 10s clip was recorded first with Carson, then the PVS-14 dismounted and the front and rear lens assemblies replaced with RPO, and re-recorded. The videos were imported into Adobe Premiere for cropping, zooming, and re-sizing only.

Observations:
There does not appear to be any perceived performance difference between the two in terms of light transmission or low-light performance. The footage does not appear to differ in terms of increased brightness nor reduced noise. As the scene was specifically chosen to be a threshold lighting situation where noise was present, if the RPOs or Carsons exhibited less noise, it would mean that more light was entering the image intensifier but this did not seem to be the case. The larger exit aperture on the RPO does not seem to provide any tangible improvement benefit.

There is however, some pincushion distortion present on the RPO, as can be seen on the edge-crop (3rd sequence, observe the vertical bookshelf support). This distortion appears to be mild but is visible and noticeable when panning the device left and right when viewing vertical lines. This may be of concern for users who are using this in urban environments where these are more prevalent. 

Conclusion (so-far):
This was only one set of lens against one scene. Additional testing is required but early indications show that the practical optical performance gain is negligible or non-existent. It could be conceivable that RPOs have a higher performance benefit in specific lighting scenarios with specific light sources (eg: sodium-based, or LED-based street lamps, as an example). The weight differential between RPO and Carson is substantial and warrants additional investigation and consideration for applications where weight is a concern with a trade-off being slight pincushion distortion.

Full-resolution screen captures:

Carson:

RPO: