Making do with the "wrong" lens...
One day I was walking around with only my crop sensor Nikon DSLR and a 50mm prime lens. In my opinion, this is a bit tight as a general walk-around lens on a crop sensor camera, being the equivalent of a 75mm, and it's certainly not the ideal gear for capturing birds in flight... but there I was in the park and people were feeding the birds, drawing in swarms of ducks and geese. I had to at least try for some shots!
You can get pretty close to the birds in the park because they're about half tame. I wanted some in flight shots so I set the shutter speed to 1/1250 seconds. (A little faster like 1/1600 or 1/2000 would freeze the bird's wings completely but let in less light, and I don't mind a bit of motion in the wing tips in any case.)
It wasn't all that bright out, so I opened the aperture all the way to f/1.8. This creates a shallow depth of field, and the background softens or blurs a bit.
The last thing to consider was the ISO, and I decided to use auto ISO with a maximium of 1000. I'm not comfortable going much higher on this camera.
In post processing I have cropped these shots quite a bit... too much to make good prints larger than 8" x 10", but good enough for use on the web. As I've said, this is the wrong gear and the wrong way to do it, but here is an even more ridiculous example...
This last shot was captured with the same Nikon D7100, but this time I had only a 24mm prime lens with me. So why am I telling you all this? Perhaps it's just a reminder to remember your long lens, but if you don't have it, don't be afraid to push a little with the "wrong" equipment when the need arises. Thoughts or questions? Let me know in the comments, and thanks for reading!