Sam6644 wrote in post #14463961
When you stop the 2.8 down to 4, it will be sharper than the 4 is at 4.
I don't know about 2.8 at 2.8 vs. 4 at 4, but I bet it is sharper.
2.8 lets in twice as much light as 4. IS is neat, but there is no substitute for letting more light hit your sensor.
Its pretty much splitting hairs when you compare f4 to f4. The f4 IS has a slight lead at 70mm, the f2.8 is a little better at 135mm and its pretty much a dead heat at 200mm according to the copies Brain tested:
http://www.the-digital-picture.com …omp=0&FLIComp=0&APIComp=0
I went with the f4 IS, but it was a hard choice for me. The lightweight f4 really sold me.
Well we don't need DSLRs either but they are a lot handier than iPhone cameras. IS is useful and I find myself glad I went with the f4 IS over the 2.8 non IS because I tend to use it for portraits a lot more often than just the outdoor sports I bought it for. IS helps to balance the ambient lighting and gives you more options for shooting informal portraits. If you follow the thumbrule of 1/fl*crop, for me using a 7D, I need 1/320" at 200mm. With the f4 IS, I can go 2 stops slower and still get a subject blur free shot at 1/80" for portraits. Now this will not help me for sports, but with human subjects posing for you, the f4 IS does give you a 1 stop advantage over the 2.8 non IS
Maybe at some point I will get the 2.8 IS II and trade the f4 IS in, but I think I will get the 135/2 instead for when I need faster than f4.