I wanted to spend today discussing lenses, but it's such a broad topic that I don't feel prepared enough to go in-depth with. Most mirrorless camera kits now come with a kit zoom lens, with a range of from 14-55mm. Sony's NEX cameras come with a 18-55mm E-mount lens, Samsung's NX cameras come with a 20-50mm lens, and Panasonic's GF cameras are equipped with a 14-42mm lens. For first-time buyers interchangeable lens buyers or point-and-shoot users, those numbers don't mean much--they may be more familiar with a zoom multiplier vernacular. These focal lengths aren't difficult to comprehend--the basic gist is that the lower end indicates how wide your shot will look, and the higher end indicates how much you can magnify. There are also a bunch of additional factors to consider--how wide the lens can open (ie. how "fast" it is), the minimum focal distance, sensor crop, etc. But if you're just getting started, it's easy to understand that zooming out means you get a wider field of view while zooming in gives you a narrower field of view.
When I first got my NEX, I shot mostly with the lens zoomed all the way out to 18mm. The reasoning behind this was that zoom lenses typically let the most light in (ie. are fastest) when they're zoomed all the way out. At 18mm, my lens could shoot at f/3.5, while at 55mm, it maxed out at f/5.6. A wider aperture means the shutter speed can be faster to produce the same image, so I don't have to hold the camera as still to get non-blurry images.
But something I didn't take into account was lens distortion. It's something that Harrison briefly mentioned in this week's build log when talking about using reference photos to create blueprints. Zooming all the way out might grant the widest aperture and look cool (especially for animal photos), but the image isn't an accurate representation the true shape and scale of your subject. 18mm isn't quite fish-eye, but it's wide enough to distort edges that look straight to the naked eye. For product photography that I shoot at the office, this matters quite a bit. Compare the shot of the model delorean above at 18mm to one that's zoomed into around 35mm below. With the side by side comparison, the difference is really clear, in a way that may not be apparent when taking the photo.
That's why I always turn grid lines on if a camera allows it. And not just horizontal and vertical lines, but diagonal ones as well. The gridlines help me identify proper straight edges on my subjects, so I know how much to zoom in to make sure the image isn't being distorted.
Do you turn on gridlines when shooting photos? And if so, how do you use them?