The Brief

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 of the last exercise you can see that their ‘perspective geometry’ is exactly the same.   To change the way things actually appear, a change of focal length needs to be combined with a change in viewpoint.

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 precisely the same way in the viewfinder and take a second shot.  Compare the images and make notes in your learning log.

My Approach

My approach to this exercise was largely driven by the subject, or lack thereof.  Instead of a portrait of a person as in both the brief and other student work on this exercise, I elected instead to demonstrate the same effect with an inanimate subject while out walking.    I used my Nikon D4 with 70 to 200mm f2.8 lens which combines the ability to zoom over the most generally usable focal lengths and open to a very wide aperture.  For this exercise, however I would need a fairly small to medium aperture in order to preserve background detail in both shots, particularly the one a the longest focal length.  In this case, when the subject is significantly separated from the background the details are lost when the aperture is too wide resulting in the effect the Japanese call ‘bokeh’.

It was an overcast winter day, so the ISO selected was 800 and both photographs were shot at f8 in Aperture Priority Mode.   The subject I settled on was one of Malvern’s Victorian gas lamps.

The Images

Focal length of 200mm

Focal Length of 70mm

Reviewing the images

The first challenge with this exercise was finding a subject that had sufficient room in front of it to allow me to move from the 200mm composition to the 70mm.  This lamp is situated on a terrace that provided this distance and also position the subject on a similar plane to my elevation.  However, it’s immediately noticeable that the angle changes that are produced by changing focal length and position when recomposing, causes the lamp to appear elevated in the 70mm image.  This is most noticeable looking at the top cover of the lamp in the 70mm shot, which looks a little compressed.  While the subjects in both photographs look the same, they do have slight differences like this one.

Looking at the background, it is clear the apparent distance to the next pair of lampposts has increased with the shorter focal length and that the tree behind now dominates the background.    An expected consequence of using this subject with the sky behind it is the change in exposure between the two images.  My camera was set to evaluative matrix metering which takes an average across the whole frame.  With the increase in sky behind the subject, the camera’s response was to close down 1 stop to 1/320th second to keep the sky within an acceptable exposure.  The result, of course is the subject being underexposed, but I think the perspective demonstration is effective.

In conclusion, I looked at a number of my own photographs using my collection of lenses for the D4.  I have previously used lens distortion effectively in landscapes to give depth and portraits to present a pleasing representation of the face, but hadn’t noticed the way the a background changes when the subject is maintained ‘close to normal’.