Low-key photography

You’ve probably guessed already that low-key light is the opposite of high-key light, the yin to its yang. High-key lighting focuses on light tones and whites; low-key lighting relies on shadows, deep blacks and darker tones, with very few whites and middle tones. The mood is opposite, too – while high-key lighting is hopeful and optimistic, low-key lighting is somber, mysterious and moody, dramatic or even ominous depending on the subject.
High-key images are flatter with less contrast than an image that qualifies as mid-key, which is most of the images that photographers produce. Low key images, on the other hand, tend to have a lot of contrast, with the primary impact coming from the shadows.

Studio lighting for low-key photography:

A low-key studio set up is a lot simpler than a high key one. You just need a single light source and a dark or black backdrop. You may find having a reflector on hand can be helpful, too, though in many cases all you will need is that single light source. As a general rule, keep the light off of your back drop and on your subject, but other than that you have a lot of freedom as far as where you choose to place your light source.

Examples of low-key photographs:

References:

1. Peterson, D. and Profile (no date) How lighting affects the mood of your photos. Available at: http://www.digital-photo-secrets.com/tip/3558/using-lighting-style-to-create-mood-high-key-and-low-key-lighting/ .
2. Pinterest (no date) Available at: https://ro.pinterest.com/search/pins/?q=low%20key&rs=remove&term_meta%5B%5D=low%7Ctyped&term_meta%5B%5D=key%7Ctyped&remove_refine=fashion%7Ctyped (Accessed: 2015).