I used to tell amateur photographers that you should spend 50% of your time working on improving how make photos with your camera and lenses and 50% of your time on digital darkroom (i.e. Photoshop or Lightroom) techniques. As one gets older, though, and as a photographer becomes more seasoned, your ability to use a camera and/or lenses starts to plateau. However, there's always more to learn when it comes to your digital darkroom.
Every so often I like to revisit old photos and see if I can improve on how they look using new and improved digital darkroom techniques. Often the original version looks like crap. I was either in a hurry or I simply did not have the expertise to rescue a photo that was underdeveloped or suffered from poor lighting and color. The photo below is one of those examples.
The day I photographed this photo it was very, very dark and dreary. I tried in vain to improve the images from this day in the digital darkroom but I failed again and again. Recently, however, I revisited them and was pleased with the new results. My Photoshop and digital editing skills have improved dramatically over the past five years since the photo on the left was first edited. Move the slider back and forth to see the difference between the two images. I think you will agree that the photo of the cowboy on the left is much better than the same photo on the right.