Posted this in the Graphic Design forum with no luck, so thought I'd try here, where it's quite likely many of us are hooking up to external monitors occasionally. Sorry for the double post. When I attach my MacBook Pro 13 (2012) or MacBook Air 11 (2012) to my 23" Samsung LCD monitor and try to use one of my Wacom tablets (Bamboo Fun, Bamboo Capture, Intuos 4), the pressure sensitivity becomes really messed up. Without a monitor attached, I press lightly with the stylus (opacity and flow set to pen pressure) and very gradually build up lines (when drawing) and tones (when painting). The pressure sensitivity is extremely precise. When attached to a monitor, the levels of sensitivity are greatly reduced. If there are 1024 levels of sensitivity, it seems to jump from 0 to 100 to 300 to 500, etc. There isn't a gradual increase. I think I've narrowed it down to the Intel HD4000 graphics. I have tried three different monitors, two different hdmi cables, two different rocketfish mini display port to hdmi adaptors, and three different Macs (the Pro, the Air, and a 2012 Mini that I briefly owned). The only common factor is the HD4000. When using an older Air (2010 - NVidia 9400m) and an older Pro (2008 - NVidia GeForce 9600GT), the pressure sensitivity is fine. The Wacom tablets aren't the problem (I've tried three different ones). If anyone can replicate this and confirm my suspicions I would be grateful. Please note: using a 2012 15" Pro, even though it has HD4000 graphics, cannot replicate the problem as it switches to the dedicated GPU when attached to an external monitor, and thus the Wacom tablet will work properly. If it is the HD4000 I'm a bit disappointed. I was hoping to be able to use a portable computer and attach it to a Thunderbolt display for painting. Pity they removed the dedicated GPU from the higher end Mini. Any help would be appreciated guys. Thanks.