Exercise 2.3: Focus

Find a location with good light for a portrait shot. Place your subject some distance in front of a simple background and select a wide aperture together with a moderately long focal length such as 100mm on a 35mm full-frame camera (about 65mm on a cropped-frame camera). Take a viewpoint about one and a half metres from your subject, allowing you to compose a headshot comfortably within the frame. Focus on the eyes and take the shot.

Wide apertures create shallow depth of field, especially when combined with a long focal length and a close viewpoint. In human vision the eye registers out-of-focus areas as vague or indistinct – we can’t look directly at the blur. But in a photograph, areas of soft focus can form a large part of the image surface so they need to be handled with just as much care as the main subject.

Don’t forget that the camera’s viewfinder image is obtained at maximum aperture for maximum brightness and therefore at the shallowest depth of field. Use the depth of field preview button to see the actual depth of field at any particular aperture. It’s surprising to see the effect that a single f stop can have on the appearance of an image.

Response

For this exercise I used a Canon EOS Kiss X4 with a Sigma DC 18-250mm 1:3.5-6.3 HSM Lens. As instructed, I took 3 exposures at a focal length of 63mm at F-Stop 5.6, 8 and 11. All exposures were taken with the camera set to aperture priority mode (AV), which can be viewed below:

  • Aperture: ƒ/5.6
  • Camera: Canon EOS Kiss X4
  • Taken: 9 June, 2019
  • Focal length: 63mm
  • ISO: 100
  • Shutter speed: 1/13s

  • Aperture: ƒ/8
  • Camera: Canon EOS Kiss X4
  • Taken: 9 June, 2019
  • Focal length: 63mm
  • ISO: 100
  • Shutter speed: 1/6s

  • Aperture: ƒ/11
  • Camera: Canon EOS Kiss X4
  • Taken: 9 June, 2019
  • Focal length: 63mm
  • ISO: 100
  • Shutter speed: 1/3s

I imported the Raw images into lightroom and exported them to JPEG files with no further processing. Normally with Raw images I would add some sharpness in post processing, especially having taken these exposures handheld. There are a number of differences between these exposures, the most striking of which is the light absorbed by the sensor with each 1 stop increase, which in turn increased the exposure time of each shot by double. This also affected the sharpness in the photos, no doubt down to my poor grip on the camera and a good reason to use a tripod for this exercise. The other noticeable difference is the detail in the background becomes more defined with each increase in F-stop thus reducing the depth of field.

  • Aperture: ƒ/5.6
  • Camera: Canon EOS Kiss X4
  • Taken: 9 June, 2019
  • Focal length: 63mm
  • ISO: 100
  • Shutter speed: 1/13s
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