(I don't own a LDC, happy with my 184's and 105, but anyhow)

Is a LDC like the U87 in the omni position influenced by the proximity effect ? I know that a pressure microphone is not influenced. But a LDC also uses a backside that is further away from the source, what in the cardio position causes the proximity effect.

Looking at the characteristics of switchable LDC's, I recognized a small boost at 4 kHz 90 degree in the omni position. There is a lot more room at 90 degree than at 0 degree. So, is the microphone more sensitive to ambient noise than a SDC omni ?