I hear a lot of people claim long lenses are not hand-holdable, or not for long. But I can take pictures for hours with my 300mm f/2.8 even with a 1.4x or 2x TC because I use the handhold attached (photo by Ron Reznick). And of course while I'm not taking or setup waiting for a shot, my arms are down. So I can walk or hike and take photos using this handhold for hours even with a 600mm.
Since the furthest the camera can be away from my eyes with that handhold where the stability provided is still effective is about 2 inches, it's impossible for my eye to focus on the back LCD screen when it's that close.
So I guess if I were to get one the K-01 would never go out with me on an outing when I'm using my heavy glass?
That makes me have to think long and hard if I'd get one for that reason.
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