Lag time in switching viewer nodes

Is their a reason why when I click on viewer nodes to see them in the image editor view they have to sit and calculate ? Like they have a black box and counter till they show up. Very annoying

Whatever state you have the “Skip Unused” button set to, change it. (I think that’s it’s name…on the compositor window’s header) This should cause blender to only have to calculate any changed nodes in that branch of the tree.

turn off the OSA, RAY, MBLUR etc options while you are just playing around.

Those have nothing to do with post calculation times.

I think they might if a RenderLayer node is being used…

Only at render time. All node based calculations occur post render hence the term “Post”. The options you mentioned are rendertime operations only.