Adding impact to photos
Impact or punch is added to photos by ensuring we make the most of the scene. If all is grey then the image looks weak. High contrasts make the image stand out more.
The second image is more impactful simply becauses it uses darks and lights in close proximity to each other.
To acheve the same effect on a photograh we can stretch the histogram to make the lights lighter and the darks darker. Boosting the contrast like this is often all that needs to be done.
However we may want to go a step further and use the curves to adjust more of the image values.
Different software have different versions of the curve tool, but they all work in the same way. By taking the diagonal line and converting it into an S shaped curve you can boost the darks and lights in a more controlled manner.
It is usually best to make a duplicate layer of you photograph and apply the curves and histogram stretching to that. Then if you find you have overdone it you can reduce the opacity of that layer and let the original exposure come through more, adjusting the opacity until you are happy with the result.
The curves tool can also be applied to specific colours to add impact on selected tones of a photograph. This can really help draw the focus of the viewer to the part of the picture you consider to be the most important.