Originally Posted by Hermitt
Edit: I guess the way that I understand this is that with dslrs, the apreture doesn't move until after you click the shutter button, the DOF preview actually closes the lens to the selected apreture setting for you to view the desired results before snapping the photo. So I was mistaken about it showing what would be the sensor's view.
ah....OK...you were misleading everyone
Yeah, it sounds like your mirror isn't moving (if it were, you'd at least see the viewfinder "blink" as the mirror swings). DOF preview is common on most SLRs....works out really well on 50mm and telephoto lenses as it will let you guage how much of the area will be in focus (though your viewfinder might get really dark when going down to 16 or more). Most SLRs have a DOF button right on the body: it's one of my memorized functions that I don't have to look away from my viewfinder (I've also managed to memorize where the tiny little WB, ISO, and metering buttons are so I can change most through the viewfinder on my 5D).
These "live previews" are actually ways that you can get the lens view onto the LCD. So a select few dSLRs that actually have this feature will either swing the mirror up so that the image goes from the viewfinder to the sensor. Or they will have a transparent mirror that can both reflect light to the viewfinder and allow light to pass to the sensor. Since I'm used to film SLRs, I don't see the point of it myself...but eh
RE: Canons for wedding photography.....yeah, I just was at a wedding: all the pro photographers were using Canons: either the 5Ds or 1Dss. Think Canon is owning the wedding business because of full frame sensors. But the 5D or 1Ds can be overkill for someone just getting into photography
As for lenses, I'm sure it would probably be debatable as to which brand makes the best optics (though I've got no doubts that my EF 135mm 2.0L is the closest thing to perfection for a portrait lens
). Both Canon and Nikon make some winners and some losers. When you start debating about the camera bodies, there are going to be some distinctions. But at the basic functionality, you'll find any dSLR satisfying. IMO, the main thing is figuring out which one is the most comfortable for you.