Passing SD and HD video through a HPF

The very basic principles of RC HPF's tell us that all else equal the frequency and the value of the capacitance are inversely related. This suggests that the largest acceptable capacitance value should be much less for the higher frequency HD video then that of SD. However, after conducting many tests using the pathological test (PLL test simply strings 20 bits in a row together of 1's then 0's instead of having a transition every bit, effectively reducing the frequency in both SD and HD by the same factor) we have found some different results. The largest acceptable capacitance values that do not kill the signal were MUCH lower for SD (1 micro compared to 4.7) than they were for HD. This seems to contradict first principles of HPF's, so what else is could be going on?

Any insight is greatly appreciated.