How would the eyebox/ clarity/ low-light performance of an SWFA Ultralight compare to a good 1-8 or 1-10 LPVO?

[Meanderthal]

Agreed that the SWFA isn't on par optically with the NF. It's great for what it is but it's very little. I have one with a plex reticle that stays at 8 power and under. It does what it's supposed to reliably but I'd choose something else if weight and cost were less of a concern.

 

[Macintosh]

Like is it fair to expect any $400 3-9x40 to be better at seeing a deer in the twilight shadows under a tree at 8x than a $4000 LPVO?

No, its not.

I dont own a 1-8 or 1-10 lpvo. But I do own a 1-6lpvo that has a noticeably better eyebox and longer eye relief than one of my 3-9’s from the same manufacturer, as well as better clarity that to my eyes results in at least functionally similar low-light performance. Even if very common this stuff is not necessarily an “inherent” feature of higher-x erectors. And while exit pupil has a lot to do with light transmission, it isnt the entire story. It is the sum of all those qualities that separates an optic, and different scopes have different combinations of qualities. You can make some generalizations, but its pretty easy to find exceptions.

 

[nm.otter]

where's the point where a basic "traditional" scope, with a larger objective, optically outperforms even the best LPVO's at magnification, simply because of physics?

Read up a bit on exit pupil.

TL;DR:
Divide the objective size (in mm) by the magnification factor. Higher numbers are better in low light and less fussy about the exact position of your eye in relation to the eyepiece.

7mm is about as good as it gets for a young, healthy human eye.
5mm is comfortable and OK for most people in most conditions.
3.2mm is fussy and jumpy in good light. It absolutely sucks in low light.

All of that comes before you factor in the 'glass.' A higher spec optical system can make up for some of the above (and may bring other benefits), but ROI drops pretty quickly.

The low light performance of the SWFA 6x42mm MQ ($350) surprised me.

 

[Begle1]

Thanks to KauaiHunter I tried out an SWFA Ultra Light and was pretty happy with it. Definitely in the market for one now. The eyebox seemed plenty forgiving enough to use at any magnification level.

When I think "tight eyebox" I think of precision shooting scopes with 30-60x magnification through 40-60mm objectives, like the sort air gunners use. I was awfully confused the first time I tried to get behind one of those. "Is this broken?" I thought to myself as I chased a marble of light around a black circle. I know there's more to eyebox than exit pupil size, but I reckon when the exit pupil gets below 1mm that provides another sort of experience entirely.

For the sake of reference, SWFA says the outer diameter of the objective on the SWFA Ultra Light is 38mm/ 1.5”. (I couldn't find that spec online anywhere, I had to ask them.)