Yes, #3 I think is a bigger factor now than it used to be, unfortunately.
My old Swaro CL 8x30 performed a little better in dim light and of course when I used 7/8 x 42 bins I didn't have any issues to speak of.
The bigger exit pupil is helpful on those dim mornings.
Also, any bino I've used with a moderate or very fast focus seemed to take more fiddling the focuser to get optimal sharpness.
I'd say the MHG has a moderately fast focus speed compared to bins I've owned and tried.
Beth, when light levels drop low enough so that our visual acuity drops dramatically, the view disconnects somewhat from the Exit Pupil size - especially if your own eyesight introduces a whole lot of other aberrations as your pupils dilate as well. Sometimes, what is seen under those low light conditions with a larger Exit Pupil bin is just a relatively brighter view of 'mush' as opposed to sharpening that 'mush' up to any significant degree.
The proviso is that with those larger Exit Pupil bins, if that is achieved by reducing the magnification rather than massively bumping up the objective size (into the 56mm, 63mm+, size etc) ,ie. say in the case of your former 7x42 with a 6mm Exit Pupil - that, that brings a couple of benefits to compensate. Namely the greater Depth of Field of the lower magnification, and the usually, wider Real Field of View. These aid in low light viewing, and Holger even mentions this in the text of his paper. On the downside though, is that the lower magnification gives a smaller image size, which is more difficult to pick up details with lower visual acuity.
The ideal of course is to increase magnification (and stability) , AND Objective size for better low light viewing, but then you know - pesky physics ...... WEIGHT arrrgh !
All of which is to say, that in reality, I don't think you are missing very much at all with your little 8x30. According to Fig. 6 in Holger's paper, the 7x42 only draws level in contrast gain at the start of the twilight zone (deep dark shadows may also have similar lighting levels) and then on into darkness.
What you are losing in ease of eye placement you are making up for in a ~40+% reduction in weight. You could possibly eek out a smidge more optical performance by going to an 8x32 - particularly the Zeiss FL, or Swaro SV, but even then you are looking at a non-insignificant ~5 Oz weight increase from your 8x30. Even better (if it fits with glasses wearers) would be the Kowa 8x33 Genesis XD. Going to the larger, heavier 8x32 Nikon EDG, Zeiss SF or Swaro NL kinda defeats the purpose even more, as they are pushing the lower end of 42mm size and weight.
Still, even with 8x33 we are only faffing about at the edges - the gains will be there over the 8x30 but minimal. It will extend parity with the 7x42 in low light up to about a third of the way through twilight. Far better gains come from going to a 10x42, and really if weight is a factor then the Nikon MHG is the one to beat. Of course a 10x50 is even better, but that's another weight class up again.
All of that is to say that don't think you are missing a massive amount with the 8x30 - it actually holds it's own quite well.
The other point you brought up that made me think, particularly in relation to low light for the first time, was focus speed. Here I was thinking back to my sporting days and how utterly hopeless I was at focusing on things coming towards me - tennis balls, cricket balls etc. Bigger volleyballs I could kinda handle. I was so bad at refocusing on tennis balls that I just gave up and took up squash - didn't matter then that I missed the ball on the way to me - I'd just get it on the way back off the wall ! Normally I like a fast focuser for keeping up with falcons and geewhizzits etc zipping through the woodlands.
However, it got me to thinking that in low light where your visual acuity has plummeted, could a fast focuser (particularly using a shallower dof bin like a 10x42) be too fast ? ie. it would be like those high speed balls coming toward me and my focus accommodation physiology just wouldn't be able to keep up in the low light. It would be interesting to hear from some of the more studied members knowledgeable on the science of physiology on this.
Anyway, I think it's important not too expect to much, or beat ourselves up too much about our eyesight or optics performance in low light. Some things just aren't possible on moving targets in dense cover using highly portable bins.
Chosun 🙅♀️
www.birdforum.net
webvision.med.utah.edu
