For what it's worth, this is very much a minority opinion. Most people who own 10X binoculars use them unmounted almost all the time. I certainly do.
I use both 12X and 15X binoculars hand-held fairly regularly, but it does require putting some thought and effort into finding a truly stable position for your body and arms. A reclining chair is probably best, but lying on my back on the ground works well, too. A picnic bench offers many possibilities, and a regular chair (with a back) is much better than nothing.
The issue has much more to do with magnification amplifying vibration than with weight -- at least for me.
To add to Tony's comments:
- The stability of a binocular seems to depend on more than just magnification. Length and weight both can work in your favor, that is until your arms get tired.
I have two pairs of 70mm Orion Resolux binoculars, 10.5x and 15x, Both weigh about 5 pounds. I can hold them both quite steady, particularly the 10.5's which seem to be rock solid.. But I can only do this is short spurts, probably a minute or so at a time. Of course reclining on a zero gravity chair makes things easier.
- In terms of the image magnifying the vibration, I think longer binoculars have an advantage because the amount angular change in the image is less for a given hand motion.
- As far as 12x or 16 x in the 50mm size, the 16x AES have a 3.5 degree TFoV, the 12x have a 5.5 degree TFoV. My 15x70s have a 4.4 degree TFoV, I think 3.5 degrees is pretty narrow for something without a finder.