7. Are the tripods acceptable for Canon,Nikon cameras? 

A: Yes. They work very well forAll DSLR SLR Cameras,for example:
 Canon EOS 1D, 1Ds Series
 7D, 5D Mark II, 5D Mark III, 60D, 50D, 40D, 30D, 20D, 10D
 650D, 600D, 550D, 500D, 450D, 400D, 350D, 300D,  1100D, 1000D
 Canon EOS Digital Rebel T4i, T3i, T2i, T1i, XSi, XTi, XT, XS, T3
 Nikon D3s D3x D3 D700 D300s D300 D200 D100 D90 D80 D70s D7000 D5100 D5000 D3100 D3000 D60 D40X