I love plein air if the weather and time is permitted. However, I don't always have that luxary to paint outdoor. That's when my digital camera or smart phone comes in. The technology today allows us to take photo reference so easily, we are able to paint any scenery at the comfort of our own place. But there are things to watch out for when taking photo reference.

Camera Lens vs Human Eyes - The above two images are taken at the same location, I was standing at the same spot. The first one was taken by an iPhone, the second one was taken by a digital camera with 50mm lens. The field of view of our eyes are closer to the image on the right. It is important to note that while smartphone is the most convenient way to take photo reference, the lens on it is much wider than how our eyes see things. You can take a more visually correct image by zooming in or corp it afterwards. But do not paint from the photo 1 to 1! If you do that your image will end up looking distorted as the perspective become too extreme to feel natural.
Soak it in before you take the shot- Another thing is before you snap the photo, stand there and spend some time to absorb the environment and get the feel of the place. Try to remember the light, the scale and most importantly, the depth of the place. Photograph is a 2D image, but we live in a 3D world. If you copy a photo without processing the image yourself, you are copying from an already processed, flat image instead of a living, breathing environment. When I paint from photo reference I would take things out, move things around and add things if necessary. You are not a copying machine, the photo is just there to remind you about the place. And that brings to the next point.
Own your image completely- I never paint from photograph that I did not take myself! For two reasons: 1. I want to paint places where I actually did go and experience. 2. I do not want to paint from a photo that I do not own. I did paint from someone else's photo before, but that's only for commission piece and with his/her permission. But for yourself, you want to own your image completely. After all, what's the point of telling your story that never happened?