ahsosl1e8 said:
1) Using viewfinder to frame pics. I'm used to using LCD to frame pictures. Whats better about viewfinder? Won't it be troublesome when objects are in difficult positions... like if taking macro shots on insects on the ground then u are forced to lie down
Also will it be problematic for ppl wearing glasses?
An SLR viewfinder is more accurate than a cheap inverted Galilean telescope-type viewfinder of compact cameras, but less accurate than the live preview on the LCD of a typical digicam. The advantages of SLR viewfinders are image clarity (no pixels) and immediate response (most digicam's "live" preview flickers & lags behind what's actually happening). SLR viewfinders can also have some advantages for manual focusing, but this has been largely negated in cheap DSLRs by the miniscule size of the viewfinder image and the removal of optical focusing aids that were standard in the pre-autofocus days.
Compact digicams have a lot in their favor for macros - not only that you can see the viewfinder mroe easily, but they (and their lenses) are also smaller and therefore less likely to block the light that is supposed to illuminate the scene. (With a typical SLR, you may not even be able to get close enough to your object, e.g. for taking "street level views" of architecture models). They typically also cause less vibrations (less mechanical action), and the relatively larger depth of field (assuming a compact cameras sensor is smaller than the DSLR's sensor) can also greatly help. For many technical micro/macro applications (e.g. mounting a camera on a microscope), there's no doubt which to prefer.
The main advantage of a DSLR may not be related to the viewfinder. Compact digicams have largely evolved from the computer-add on gimmick side of things, meaning that their usability for taking photos is frequently horrible (navigating through menus to change basic settings, if they allow to change settings at all), and their performance is often only so-so. Most DSLRs have evolved from traditional film SLR systems, carrying over more practical user interfaces (dedicated knobs/buttons for basic functions). And, of course, with a typical DSLR, you can change the lens, while you cannot with a typical compact digital camera.
There is no technical/fundamental reason for the differences mentioned in the last paragraph. This is just how the market reality is. If electronic viewfinders improve and some secondary issues with the shutter are addressed, they may obsolete DSLRs at some point in the future.
2) I've some older film slr lens. I heard that they can fit dSLRs with the same mount but must multiply focal length. In that case, does that mean that a 50mm nikon older lens will become 50 x 1.6 = 80mm on a new d50 for example?
No. You can read this in many places, but it is utter nonsense. DSLRs with smaller sensors effectively crop the image (compared to the traditional film format), so the field of view is indeed that of a lens with longer focal length. BUT, this is not equivalent to using a longer focal length lens on a "full frame" SLR. For example the depth of field of a 50mm lens on a DSLR with a 1.6 crop factor will be different from an 80mm lens on a "full frame" camera.
