Who's DOF? Read on and find out!

DOF isn't a who, it's a what. It's week "lucky 13" in the Pet Photography 52 Week Project and we're in our first week of a "shelter in place" order by Dallas County in an effort to slow the spread of the novel Coronavirus that has been sweeping the globe. With all the extra time on my hands, I wanted to photograph something new for this week's theme in the project; "shallow depth of field" (or DOF), but had to get creative due to restrictions as a result of the order, so I walked out my front door and photographed one of my own dogs in my neighbor's front yard.  

Gracie's got a pretty good stay so I rolled through a series of aperture settings to demonstrate the difference between a shallow depth of field and deeper ones. I never moved my position from my subject and used the reciprocity rule to keep the exposure consistent; you can read more about that here. Despite my lens going to f/1.4, I started at f/1.8 and then repeatedly adjusted a full stop and snapped a new frame all the way up to f/14. See below for that series, straight out of the camera - no retouching. 

A device called a diaphragm serves as the aperture stop, and controls the aperture. The diaphragm functions much like the iris of the eye – it controls the effective diameter of the lens opening. A lower f-number denotes a greater aperture opening which allows more light to reach the film or image sensor. A higher aperture number denotes a smaller aperture opening restricting the amount of light that reaches the sensor. 

The f-stops work as inverse values, such that a small f/number (say f/2.5 corresponds to a larger or wider aperture size, which results in a shallow depth of field; conversely a large f/number (say f/14) results in a smaller or narrower aperture size and therefore a deeper depth of field.

When the aperture is large (ex. f/1.8), the area in front and behind the focus point is very slim or shallow. That means that objects right in front and right behind the plane of focus is already going out of focus. Shallow depth of field is useful in pet portraits to isolate the subject from its environment, in this case my neighbor's house and car. You can see as the aperture decreases, more and more of the house, the car and all the general busyness behind the subject comes more into focus and competes with the viewers attention - not ideal. 

(click on any image to view full screen)