As an artist I must admit I seldom paint from my photos alone, I much prefer beginning with a sketch of two “on location”. Most often I just have time for a couple of pencil sketches and possibly a quick watercolour wash over some composition sketch. Further I seldom sketch from prints but rather I much prefer sketching and painting for a screen (can be computer, TV or projected image). This is for two important reasons
1. The colour intensity and dynamic range of tones is better. Its the old slides versus prints issue.
2. I can zoom in, and pan around or tweak the image a little, such as to alter the tone or play with the colour curves) to explore what I am trying to achieve in paint.
If possible I like to take the same scene at different times of the day, and under a variety of lighting conditions, sometimes a bracket set of exposures or a HDRi image can enhance the painterly feel. Also zooming in (on detail –see below) or out (on the broader picture – see previous panoramas) can help a lot afterwards re-establish what is important as characteristic of the subject and also get an overall feel for the place. All this means maybe 10 or more photos to support the one or two sketches.
So I must admit I am leaning more and more towards a reasonable smart phone with a camera (eg an android or IPhone) as being more than adequate for collecting photo reference for later painting. The cameraphones are certainly less bulky than any DLSR. The number of digital photos you collect is not significant as they are truly “weight less”. More room in your art kit bag for extra sketchbooks, papers and paints.