Don’t forget that when you want to transform a photo into a painting, first look at the scene, person, or composition with your own two eyes if possible. Take in the view, make mental notes, and memorize the scene. Only then take out your camera and photograph your composition carefully.
As you turn photo into painting, remember that consistency in your treatment of the light source is key to a convincing painting. So look at your photo and ask yourself, where is the light coming from?
Shadows are crucial to study when you are going from photos to paintings. Often times you can lose the light in the shadows with a photograph, so be sure to interpret these hidden areas when it comes time to paint them.
Even when using a photo reference, it is important to squint. You will see patterns in your reference and avoid unwanted patterns on your canvas.
Painting from photo references can make you forget that thoughtful cropping of the scene you want to paint or draw is necessary. This will help you reduce a lot of work composing on the canvas. If you take the picture with this in mind, you significantly cut down your workload.
You don’t have to paint from photos that are large, with high resolution. Instead, use small photos of low resolution. It will help you to not rush into the details. And small, indistinct reference photos force you to simplify and reduce what you depict.