Two buddies are using different 7", 1920X1200-resolution monitors mounted to the rear of their cameras as viewfinders.
Here's one... https://www.bhphotovideo.com …finehd_on_location_7.html
and the second... https://www.bhphotovideo.com …_ips_ultra_thin_full.html
Each is connected via HDMI and each fotog LOVES the improvement in visibility, including apparent resolution and MUCH easier manual focusing. At about $300 for the monitor system and two 6600mAh batteries and a charger, I'm seriously tempted to try one, as my 74-year-old eyes are NOT getting better! With various clamps and rails I've been accumutlating for 19 years, I've patched together what I believe is a fairly rigid-yet-liteweight mounting system that will rotate with the camera for a vertical frame. Here's a pic of one friend's system. It's a little difficult to see clearly how it goes together, but all the controls on his Canon 5D3 are usable.
Anyone using a similar system?