The Great 50mm Lens

An acquaintance of mine is buying an SLR camera and my first piece of advice is what I tell everyone who is doing the same... if you buy just one lens, make it a 50mm f/1.8. She is kinda new to the SLR photography arena, so I figured I would take the opportunity to post info here rather than just on a facebook post. I'll keep it basic.

The 50mm is my go-to lens, its the lens I keep on the camera by default. I personally do not use the kit lens at all, I almost never take it with me and I can count the number of photos I take with it (albeit if you are a more casual photographer it might be better suiting). I've taken about 80% of my photos with the 50mm, and about 80% of my best photos with it.

50mm means that the lens doesnt zoom at all (its called a 'fixed' or 'prime' lens). Seems kinda lame, but because a fixed lens it has some other special properties...

• First, 50mm happens to be something of a magic number. They say that the focal length of 50mm is closest to that of the natural focus length of the human eye. So your photos will be be taken with a more 'human' perspective. This makes is a great lens for "people pictures". (if you're using a pro-sumer cropped sensor camera, this is a little bit off - but its still a very natural view point).  I believe its a viewpoint that will generally make you a better photographer.  
• Because it is a "fixed" lens, it is very fine tuned. The focus is perfectly set in the factory. There is only one moving part. On a typical lens, there are several interior lenses moving together at once to get to the best focus. Every lens no matter how big the focal range has a sweet spot where it is in best focus. The sweet spot on the 50mm is... 50mm, so its always got real sharp focus.
• f1.8 refers to the maximum size of the aperture. The smaller the number the larger the aperture. A larger aperture means more light gets in. More light means you can take pics in darker conditions. The largest aperture that you'll find in consumer and most pro grade lenses is f/1.2 ... a standard kit lens is somewhere between f4.0 to f5.0 range. So this particular lens has pretty close to the best possible aperture in existence.
• Also, without getting too technical, because the aperture is so large something special happens, the depth of field of the picture shortens alot. So when you take a photo of someone, their face could be in perfect focus but everything else fades to a blur. People love it. Its called "bokeh" and its pretty much only possible with an SLR camera.
• Its light and small.
• The best part is... its cheap! You can get this lens (in most makes) for around $100. Its not because its a terrible lens, its cheap because its relatively easy to manufacture. As I mentioned, there are few moving parts - most lenses require very precision manufacturing to perfectly time and tune the opticals.

Where to buy it:

Canon

For you  Nikon people