FILM V DIGITAL
(I realize that most people who read this will already know alot of what i say, but for that one or two people...)
the age old question (if you can call it age old)
Film is very hard to compare to digital in terms of resolution. Film's resolution varies based on the ISO of the film you are using. The grain of the film becomes visible (in prints, not on the film) when you start making enlargements when you move to film with a higher ISO. Likewise, if you increase the ISO equivilent on a digital camers, you will see more noise in the photo.
Film has a much better dynamic range than a ccd. The main reson for this is that film has high sensitivity and low sensitivty layers for RGB, all the previous ccd's have had only large photosites (the digital equivilent to grain) which are only sensitive to bright colors, this makes some thigs very hard for digital cameras to pick up, such as contrasting white on white. The first camera that has been able to approach that on digital is the fujifilm s3 pro.
Lenses are another concern of some digital photographers. The lenses of digital SLR's have more to deal with than thier film counterparts. For one, ccd's are much more reflective than the emulsion side of film. This can potential cause problems with light reflecting off the ccd then to the lense then back to the film. Another problem with ccd's is that they like light to enter them at near 90 degree angles, film is much more forgiving in that regard. This is why there are digital lenses, they counter the problems mentioned here. The rear lense element in digital lenses sits much closer to the ccd than thier film counterparts so they can have the light enter the ccd at closer to a 90 degree angle, and counter the ccd reflection problem.
CCD's are not the same size as film, many are aps-c sized so they have what is called a magnification factor when using lenses. Lenses are rated in focal lengths for 35mm film so you have to factor in the magnification factor of the lenses when determining the actual focal length. A common magnification factor is 1.5 therefore:
a 50mm lense becomes a 75mm lense
a 300mm lense becomes a 450mm lense and so forth.
if you buy a digital slr you should ask about the magnification factor so you can get the actual focal length of the lenses you have.
canon is making a line of digital lenses but i don't know if they are out yet.
nikon has thier DX line of lenses that are for thier digital slr's
both these lines of lenses can fill an entire 35mm fram, so they will work on film slr's as well, the opposite is true too, film lenses work on digital slrs( as long as they use the same mount and are compatable....)
So far there are two pro digital slr's that have a magnification factor of 1
One of the kodaks (i forgot which one)
and the Canon EOS 1D (not the mark II)