Project 1: The distorting lens – Exercise 2.5

Exercise 2.5
Find a subject in front of a background with depth. Take a close viewpoint and zoom
in; you’ll need to be aware of the minimum focusing distance of your lens. Focus on
the subject and take a single shot. Then, without changing the focal length, set the
focus to infinity and take a second shot.

The closer you are to the subject, the shallower the depth of field; the further from
the subject, the deeper the depth of field. That’s why macro shots taken from very
close viewpoints have extremely shallow depth of field, and if you set the focus at
infinity everything beyond a certain distance will be in focus.

As you review the two shots, how does the point of focus structure the composition?
With a shallow depth of field the point of focus naturally draws the eye, which goes
first of all to the part of the image that’s sharp. It generally feels more comfortable if
the point of focus is in the foreground, although there’s nothing wrong with placing
the point of focus in the background.


These two images were taken at the end of my road. The first focusing on the top nodule of a post box. This sharply focuses on the foreground and throws the background out of focus. The Second focusing on infinity puts the background in focus and throws the foreground out of focus.

They were all taken with:

  • Aperture priority
  • ISO 100
  • f/5.0
  • Fujifilm X30 equivalent 35mm focal length of:
    • 56mm
road-short-focus

Post box and up the road – Short focus

road-long-focus

Post box and up the road – Long focus

I can see that playing with the point of focus will effect the depth of field. This will be a useful technique to limit or restrict attention to elements within the image.

Project 1: The distorting lens – Exercise 2.2

Exercise 2.2
Select your longest focal length and compose a portrait shot fairly tightly within the
frame in front of a background with depth. Take one photograph. Then walk towards
your subject while zooming out to your shortest focal length. Take care to frame the
subject in precisely the same way in the viewfinder and take a second shot. Compare
the two images and make notes in your learning log.

As you page between the two shots it can be shocking to see completely new
elements crash into the background of the second shot while the subject appears
to remain the same. This exercise clearly shows how focal length combined with
viewpoint affects perspective distortion. Perspective distortion is actually a normal
effect of viewing an object, for example where parallel train tracks appear to meet
at the horizon. A ‘standard lens’ – traditionally a 50mm fixed focal length lens for
a full-frame camera (about 33mm in a cropped-frame camera) – approximates the
perspective distortion of human vision (not the angle of view, which is much wider).
A standard lens is therefore the lens of choice for ‘straight’ photography, which aims
to make an accurate record of the visual world.


Below are 2 shots I took near the South Bank Friday lunchtime with my Fujifilm X30 compact camera. The pair of images are framed on the sign. They were all taken with:

  • Aperture priority
  • ISO 100
  • f/5.0
  • Fujifilm X30 equivalent 35mm focal lengths of:
    • 112mm
    • 28mm
focal-length-112mm

Tenison Way – Focal length 112mm

focal-length-28mm

Tenison Way – Focal length 28mm

The difference in the view between these two images is striking considering the fact that the subject occupies the same space in the frame.

Project 1: The distorting lens – Exercise 2.1

Exercise 2.1
Find a scene that has depth. From a fixed position, take a sequence of five or six
shots at different focal lengths without changing your viewpoint. (You might like to
use the specific focal lengths indicated on the lens barrel.)

As you page through the shots on the preview screen it almost feels as though you’re
moving through the scene. So the ability to change focal lengths has an obvious use:
rather than physically moving towards or away from your subject, the lens can do
it for you. The other immediate difference between the shots is the ‘angle of view’,
which also depends on the sensor size of your camera. Use the sequence to try to
get a feeling for how the angle of view corresponds to the different focal lengths
for your particular camera and lens combination. Which shot in the sequence feels
closest to the angle of view of your normal vision?

Does zooming in from a fixed viewpoint change the appearance of things? If you enlarge and compare individual elements within the first and last shots, you can see that their ‘perspective geometry’ is exactly the same. To change the way things actually look, a change in focal length needs to be combined with a change in viewpoint.


Below is a sequence of 5 shots I took on the South Bank Friday lunchtime with my Fujifilm X30 compact camera. The sequence does give the appearance of travelling through the image. They were all taken with:

  • Aperture priority
  • ISO 100
  • f/5.0
  • Fujifilm X30 equivalent 35mm focal lengths of:
    • 28mm
    • 35mm
    • 50mm
    • 85mm
    • 112mm

Of all the images taken, the image taken at a focal length of 50mm appear to me the closest to normal vision.

focal-length-28mm

South Bank – Focal length 28mm

focal-length-35mm

South Bank – Focal length 35mm

focal-length-50mm

South Bank – Focal length 50mm

focal-length-85mm

South Bank – Focal length 85mm

focal-length-112mm

South Bank – Focal length 112mm