As I continue to evolve as a photographer I find that one of the most challenging tasks is making artificial light look realistic.  It's a delicate balancing act.  Natural light, artificial light, aperture, shutter speed, and ISO all have to work together in harmony to achieve your desired result.  Getting to that final balance is no easy task.  It requires the image maker to have a intimate knowledge of each of the elements, and what their impact will be on your final exposure.

Every photographer has their own approach to lighting.  Some use trial and error until they see what they like. Others pre-visualize entire scenes and can see the final image before they even take out their camera.  Perfectionists can use light meters to tweak the exposure using 1/10th stop increments. 

What's my approach?  It varies.  It can depend on time restrictions, subject, equipment, time of day, and of course how I'm feeling at any given moment.

Let's look at a the evolution of a shot that I recently created.

This first test shot is crucial.  It shows me how the camera is seeing the scene, and where the natural light is coming from. From here I can begin to understand where my light needs to be, and how much light I will need.

Subsequent test shots reveal how my light is impacting the scene.  From here I can move and shape the light into a more pleasing source.  At the same time I can give the model instructions as to how they need to interact and orient to the light source. I will also begin to adjust light output to more closely match the natural light in the scene.

When trying to balance ambient and artificial light, I will often do a before and after comparison to see if my light is believable or not.  In this particular shot, I have included a practical (cinema term for a light source that is present within the frame) to give the viewer an realistic place that the light should be coming from.  This helps to hide the fact that I am using artificial light and makes the scene more believable.

As you can see in the final exposure, I continue to tweak wardrobe, camera position, and model position until I am happy.  Throughout the entire process I continually re-evaluate the light an shadows to make sure everything is balanced.