The focal length you choose will have an effect on the distortion of your image.
The other day I was out with some friends, and I also brought my Fuji X-T1 and 18-55mm lens along for the ride. I ordered a beer, and before having a sip I decided to photograph it. Because I was sitting close to the table, my first instinct was to photograph it with the lens zoomed in (in this case, it was set to 24mm):
The photo has some noticeable distortion, primarily at the top of the glass where it flares out and then narrows toward the bottom. I saw this and decided to reshoot it. Instead, I leaned back in my seat a bit, fully extended the zoom (55mm), and reframed it the same way as the original shot:
This second photo, in my opinion, is a much more pleasing photograph and represents the glass much better than the original. Even the glass in the background is more upright and less distorted.
What I learned about distortion:
- Photographing a scene close-up with a wide-angle focal length will add distortion to your subject.
- By moving yourself back (away from the subject) and using a longer focal length, you will reduce the distortion. You will end up with a more pleasing and natural representation of your subject.