Depth of Field and Capturing Movement are Byproducts of Aperture and Shutter Speed
Photo John Robinson
A photograph is an aspect of a moment in time. Through the found control of the camera’s aperture, shutter speed and ISO as learned in the Camera & Coffee photographic basics session we can now emphasize a photographic plane through the depth of field and capture a sense of movement in a static photograph. Depth of field and capturing movement are byproducts of the skilful use of aperture and shutter speed in photography.
Depth of field in photography is connected directly to the f stop of the camera’s lens. An f stop of f2 will give a much shallower depth of field then an f stop of f16 on any lens. A wide-angle lens set at f2 will have a deeper depth of field than a telephoto lens set at f2. The closer the focused subject is to the lens the shallower the depth of field is across the range of f stops of that particular lens from the widest f stop to the narrowest f stop.
The depth of field of a photograph aids in where you the photographer want the eyes of the reader of your photograph to visually settle.
A photograph with a very shallow depth of field could have the eyes of your subject in focus but the ears and the background and most of the foreground out of focus. This makes the eyes of the subject the primary focus of this photograph.
A picture with a very deep depth of field could have the eyes of your subject in primary focus plus most of the background and foreground in acceptable focus too, giving the subject context by including more in focus detail of the environment to this second photograph.
The photograph is a framed static moment in time. Skilful use of shutter speeds can make a photograph have a sense of movement too.
The sense of movement in photography is directly linked to the shutter speed in the camera body. Slow shutter speed will record more of the ‘travel’ of the movement while a fast shutter speed will more likely freeze the movement of the subject in front of the photographer and camera at the time.
There is a lot of fun to be had with cameras and movement. There is more than one way to record movement with photography.
The recording of movement is dependent on shutter speed, the speed of the movement and the direction of the movement concerning the position of the camera.
Slow shutter speed will blur movement a faster shutter speed will reduce the blur and fast shutter speed can virtually freeze a moving object.
As an example, I am going to photograph a person riding a bicycle past people on the pavement and cars on a road. The shutter speeds I will use are 15 or 1/15 of a second, 60 or 1/60 of a second and 125 or 1/125 of a second. I will first position my camera so the person riding the bicycle will go from my left to my right.
At 15 or 1/15 of a second, the motion of the bicyclist will be accentuated, there is a broad blur across the frame. In the photograph at a shutter speed of 60 or 1/60 of a second, my person on the bicycle is more distinct with some blur to show the movement of the bicycle to my right. 125 or 1/125 of a second makes the person on the bicycle distinct with little or no blur at all, while the car driving along beside the bicycle is still somewhat blurred in this third picture. In the first picture at 1/15 of a second, some of the people standing on the pavement have no blur at all while the bicycle has a broad brush of blur.
In my second camera position, I want the bicyclist to travel directly to me and my camera. In all three shutter speeds, the blur will be minimal, in photography, it matters how much the subject travels across the sensor or film plane and not towards the camera.
The aperture and shutter speed work together not only to produce a well-exposed photograph but can also produce interest with a combination of depth of field and the capture of movement.
I am outside in late afternoon light with my camera and take a light reading, at ISO 400 an aperture of f11 and shutter speed of 1/25 gives me a well-exposed picture. This combination also gives me with my camera a tripod a deep depth of field with a lot of blur in movement. Or with staying with an ISO of 400 I can move my aperture to f5.6 and a shutter speed of 1/125 of a second, I still have a well-exposed picture. Now, this combination allows my camera to come off the tripod at a shutter speed of 1/125 of a second and reasonable capture of fast movement.
And finally, in this set of options I stick again with a 400 ISO and as I wind down the shutter speed to 1/1000 of a second I in an equal measure I open up the aperture to f2 which is the widest in my system camera setup. With this option, I freeze the movement but depth of field wise the focus is now really only on what I have focused the lens on.
If you shorten the time the shutter is open you have to compensate by opening up the aperture in an equal measure.
Finish the coffees and take a breath…