A friend was asking me about his binoculars and I must admit I didn't have a clue. All I know is my bins are 8x42 and I quite happy with the image I get.
Anyway what exactly does
8x-24x50 and
78M/1000M at 8x actually mean
Many thanks
It sounds as if they are zoom binoculars which are variable from 8x to 24x magnification with 50mm objective lenses. The second figures probably refer to the Field Of View. At 8x magnification, looking through them at a scene 1000 metres away the width visible from one side to the other will be 78 metres (which is very narrow by today's standards). The FOV for good binoculars these days is around 130 metres. Your 8x42 bins sound like a much better proposition. Mind you, I now expect to be told that I have completely misunderstood the figures!
Ron
Zoom bins have smaller fields of view than fixed focus binoculars. At lower power, in particular, the view is claustrophobic, because the apparent field of view (how "open" the view looks) is narrow. As magnification increases, the FOV decreases but only slightly but the increased magnification makes the apparent FOV "open up".
For example, in the Nikon 8-16x40 XL Zoom (one of the best zoom bins), at 8x, you get 5.2* FOV, which results in a tunnelesque 41.6* apparent field of view (AFOV), but at 15x, you get 4* FOV, which gives you a comfortable 60* AFOV.
On the down side, the exit pupil goes down as the magnification goes up, so at 8x, the bin has good sized exit pupils of 5mm, which can take you down to twilight and beyond. At 15x, the exit pupils are 2.6mm, which can be dim on an overcast day.
At 24x, your friend's bins would only have a 2mm exit pupil, less than compact binoculars.
For general use, fixed magnification works best. Don't get fooled by the allure of magnification, not even a micro-surgeon could hold a bin steady at 24x.
Brock