which should have higher entropy?

I made a similar post sci.image.processing a while back.  I'm trying
to understand why a my natural images are higher entropy than uniform
noise.  The order from lowest to highest is

constant (0 obviously), uniform noise, LPF'd image, same image not
LPF'd, gaussian noise

My theoretical calculation for uniform noise agrees with what I'm
getting -- about 1/256*log2(256)*241^2.  Now there are nice smooth
areas in my image.  Should the entropy really be higher?  Or am I just
not doing this right.