Thanks.
 
Re-installed BENQ driver, no help.
Read the manual however and if you use a DP cable then you can manually adjust Pixel Clock on the monitor, this is if you see vertical banding that I see in the Display Port Wizard test. So i'll wait for the DP cable to arrive and see if I can fix the issue that way.
 
Did some searching for pixel clock issues and there are a few threads of people reporting display issues on 120HZ monitors with 10 series NVIDIA cards. Seems its mainly for 1440P however on bootup but wondering if there is a connection. Goes a little beyond my knowledge (I'm not an over-clocker) but seems to be a conflict that NVIDIA will need to address:

 
 

I just thought of something. I had a similar problem with image ghosting. Does your monitor have a "response time" adjustment? I get terrible ghosting when I set it to anything but "standard"

Hi,
No, no response time unfortunately. Many thanks for your help though.
Finally tried with the DP cable, no fix. More options are available in the NVIDIA control panel; Colour depth set to 32bit, Output colour depth is 8bc, Colour Format RGB, Output Dynamic Range set to Full.
 
DP doesn't support more than 60hz though either?
 
Pin pointed the issue to colour banding and it seems its a very common issue over the last year or two with various NVIDIA GPUs. Issue with the GPU card itself that NVIDIA seems to be ignoring:

 
Out of options really. Its important to me that I can edit my photography.
I'll RMA EVGA and ask if a fix is in the pipeline. If not I'll try and return and look at an ATI I guess.

Best of luck with your ATI Card!