always shoot ISO100 outside
thats not really a good idea, because you can miss shot. I also thought that iso 100 will be always enough in sunny day until i got a blurred picture of a moving train.
On most modern dslrs you cant see much difference between iso 100 and 400.
My advice would be - if you have opportunity, use auto ISO. On 60D it works well
I'm new to DSLR's, so please be patient and take my opinions with reserve. Thank you : ) Yes, i am Canon man. Google + My picasa photos My 500px album
Canon 60D + 15-85mm f3.5-5.6 IS, Canon 70-200 F2.8L
IS II, Canon 430EXII, polarizing filter 72mm,
Canon AT-1, 50mm FD F1.8