Your 450D will stop down the aperture just before the picture is taken, so it doesn't matter if you (or the camera) sets f1.8 or f22
I discovered this when trying to take photographs through a chain link fence in bright sunshine. Looked great through the viewfinder, no fence evident- operate shutter, fence!
I discovered this when trying to take photographs through a chain link fence in bright sunshine. Looked great through the viewfinder, no fence evident- operate shutter, fence!
A moment of confusion followed.