Buying lenses is a daunting task. After choosing a good camera, the wide choice of lenses intimidates most novice photographers. Aggravated by endless reviews contradicting each other and reciting technical specs like a muezzin rehearsing Quran verses, many cannot come to a decision easily.
While professional photographers often buy very high-end glass to squeeze the last bit of information out of a sellable picture, most non-professional photographers are seeking guidance for a sensible decision. Recently, I received many inquiries about this very topic. While I chose to answer a number of requests via email, I decided to summarize some information in an easy to read article.

Focal Length, Visual Space, Crop Factor, Zoom and Prime Lenses

Learn what you need to know about the focal length of your lenses to narrow down your lens buying decision.
Read how the focal length transforms your visual space and how to exploit it.
Do wide-angle lenses really have a larger depth of field?
Why would we buy a Prime Lens instead of a zoom lens?
Learn the most important answers about focal length and related issues in this part of the tutorial.

Aperture, Image Stabilization, Shutter Speeds, ISO and other lens speed questions answered.

Should you go for lenses with a wide maximum aperture or buy a lens with image stabilization instead? What are the implications on shutter speed and ISO and will you need a tripod or can you go hand-held?
In the second part of my tutorial, I am going to answer questions related to lens speed.

Recommendations, Third Party Lenses, Digital Lenses

Now we are getting serious. While learning all the technical stuff may not be as much fun, the effort will pay off in this section. Here I will talk a little about different brands and choices, but spend the majority on recommendations to the recurring question: “What lens should I buy?”

Examples, Lens Testing

In the concluding part of the lens buying tutorial I will show you the decision making process with real life examples and tell you how you should test your lenses to find out if you have a good copy or a bad one.