Thanx, Eric,
I tried to do so, but a strange thing happens:
When I use the Histogram tool with the original field applying log transformation inside the tool - I see one diagram, but if I calculate new field and use the Histogram tool without any transformation - the diagram is different. As I've understood from Help, the reason is in the algorythm used by log transformation inside the Histogram tool - it uses kriging log transformation meanwhile as the build-in Log () function is pure Log.
So there's no another way to get the same result as shown in Histogram tool?