Resampling ON/OFF (Ctrl+R)
When zooming images, a simple resizing procedure can give the fastest response or a more complex procedure (Resampling) can give better quality.
If your system is sufficiently powerful, you may choose to leave Resampling ON permanently.
Otherwise you may prefer to turn it off for a faster response.
For non-zoomed side-by-side images, it is recommended that Resampling is ON.
A toolbar button 
may also be used to toggle this mode, it is blue 
when Resampling is ON.
