When choosing a target or another many doubts assail us. The first thing the focal or focal range, then its luminosity. But even with that pair of conceptual clarity, we find several models that meet and have a price difference abysmal.

Obviously the quality is decisive but how that will influence the quality difference? So complex is a more expensive achromatic objective for that? What are the fluorite crystals and to serve? What diffraction lenses? How engines work ultrasonic and image stabilizers?

To answer all these questions it is best to read the book Canon EF Lens Work (multiple PDFs in Castilian), and in particular its chapter on EF Lens Technology (PDF) , which describes in a very technical but very understandable how each element of a goal and the design process. Obviously the book is oriented optical Canon , but the concepts of operation are the same for any other brand and is an excellent source of learning.

Furthermore, in the other chapters will find an overview of the history of the targets Canon and a detailed description of all available models (and accessories ) in September 2006, when it launched the eighth edition of this book.

We may also learn some basics of photography, as that is the depth of field, circle of confusion or other aberrations.

Without doubt, a highly recommended reading to understand better how your goals and to be the flaws that sometimes appear in photos.

And as the perfect, take a virtual tour of the Canon factory objectives (requires Adobe Flash ).