I'd suggest browsing the forum for any of the other many discussions of this topic. But I can address some of your specific questions:
Originally posted by FHPhotographer The problem: normal vision is very broad at about 120 degrees, but it apparently focuses best on a field of view about 40-45 degrees.
And focuses better still on a field of view of about 6 degrees that about what the "fovea" (a term I just learned in one of those other discussions last week) covers. Not sure where you got the 120 degree or 40-45 numbers from, but you're right, vision is very broad in general, but much of that is "peripheral", and the normal usable part is smaller. So there are senses in which our vision is best represented by the something like 120 degrees number, other sense in which it best represented by something like 40-45 degrees, and other senses in which it is best represented by 6 degrees.
None of this really explains why certain focal length are called "normal", though. As Class A says, it's about what happens when you print the image (at a typical size - this doesn't work for very small or very large prints) and then view the print from a typical distance for that size. A "normal" focal length is one that, when printed and viewed in this manner, produces no perspective distortion - all objects in the picture look to be the same sizes they did when you took the picture.
Put another way, a "normal" focal length would be one in which if you looked at a print on the wall from what felt like a typical distance, you could *just* fit it in the viewfinder if you tried to take a picture of the print itself.
Quote: Therefore, the DA-35mm lens I use is approximately a "normal " lens, but the image, seems to be "smaller" than what I see
You mean, in the viewfinder? That's simply because the viewfinder doesn't magnify the image enough. What you see in the viewfinder has nothing to do with what makes the image "normal" - it's all about what is actually captured.
Quote: and doesn't "seem" correct until previewed at 1.2x in the camera.
I assume now you're talking about the LCD. Now your problem is what I mentioned about thigns not holding for prints that are too small or too large. The LCD is basically a tiny print from this perspective, and you're viewing it from too far away for it to work out as it would if you printed, say, 8x12, and hung it on a wall.