Recently I spent a few hours at 'PAWS' in San Andreas, California (Performing Animal Welfare Society - wild animal refuge). I managed to capture this male African Lion.  He was about 300 feet away up on a hill.  In the past it would have been very difficult (let's be honest.... IMPOSSIBLE) for me to take a photo like this because of the distance and fact I shoot with a Pentax DSLR.   With the new K mount lenses that are available that fit the Pentax cameras, the updated DSLR sensors, shake reduction features, and improved auto focus (I usually shoot manual - but at that distance I tried the auto focus feature) it came out better than I could have done shooting manually and hoping my eye would be able to get the fine features.  As I have stated on many of my postings, it's a good idea to try several different settings when taking photos.  Shoot until you find what is best for you and for the conditions.  Because it was impossible to get any closer to this beautiful lion it was important that I use/have a lens that will compensate for the distance.  Even if you don't, take the photo anyway and see what you come up with...  you can always enlarge the object and crop it.