It is commonly accepted that any lens 35mm and below are considered "wide-angle", lenses 50-85mm, are generally considered as "normal" or "portrait" lenses, and Those above 85mm are usually referred to as "telephoto". Now before I get chased through the town by an angry mob waving torches and pitchforks, it is important to note that I used the words, "generally" and "usually". I realize that some people have been taught differently about what the proper nomenclature for certain focal length lenses is, but I am just using these definitions as a general guideline. With that said, it is important to think about what you will need to shoot. If you are going to be in close quarters with your subject, then it only makes sense to bring a "wider" lens. If you are not going to be able to get close to your subject at all, then you must bring a "telephoto". This part is not the part that most get wrong. Most of us understand the difference between the different lenses. What most of us seem to forget all too often is that if we are not shooting on a "full-frame" camera (35mm equivalent), then we are going to have to deal with some sort of crop factor. Now there are some lenses out there that are specifically designed for the crop sensor cameras but there are a great majority that are not. So to help you with the conversions my friends, I have decided to post this handy dandy little chart. Please feel free to copy it and save it for your own personal use and reference.
This image is from our friends at www.digicamhelp.com. They are a wonderful source for almost any question that you might have about digital photography. With this chart, and a little forethought you should be able to make some well informed decisions about which lenses you will need to bring for your next job or outing. Hopefully this will save you some lugging around equipment that you just won't use when you are out there. As always my friends, it's been fun. Keep shooting!
Here's talkin' at ya!