Probably showing my noobile tendancies here, but can someone answer this for me? I understand that apeture affects DOF, that a wide open aperture results in a small DOF, and a small aperture gives a large DOF. My question is, in an SLR, while composing the picture and adjusting the aperture, should I see the effects of this changing DOF in the viewfinder? I would break out the SLR and try and figure it out myself, but I'm stuck in class. Biochem. Ugh.