When is 50mm NOT 50mm?

sean lancaster wrote:

Exactly right, but it even goes beyond staying with the same camera for life. I pretty much learned photography by looking at images on Flickr and studying which lens was used as well as other EXIF data and also by reading photography books. Most of the books are written by authors/photographers using a full frame camera. So, I see a photo in the book that I want to replicate and it helps to know that I won't get the same frame of reference using the 50 on my NEX as the author got using a 50 on the FF camera. If you're going to communicate with other photographers and across systems then the equivalency to FF helps to better draw comparisons. Even though it's confusing to think about the crop factor, it does serve a purpose to be knowledgeable of the conversion and why it's important (e.g., when you need to apply it or not).