How to test input latency - one monitor, two inputs

[Aegis_Titan]

Hello, im wondering if there is a way to test input latency, i have one monitor and two inputs, one is HDMI -> VGA and other is HDMI->HDMI, is there a way that i could test the input lag and find which connection is slower and by how much? im certain the HDMI -> VGA connector is slower due to active conversion, but question is by how much, i wouldn't mind 1-5 ms slower but 15-20 would be allot.

 

This is the adapter -> http://gmb-online.nl/egmb/ProductSheet.aspx?id=8978&lang=1

Original Response time is 3 ms for the screen.