Saturday 29 January 2011

Exercise - Focal length & angle of view

I selected a nearby location that had plenty of reference points for the second part of the exercise.  I took my D90 with a 18-200mm zoom lens as this would give me the flexibility I needed for the 3 photographs.

Photograph 1 was the standard shot, where the objects in the viewfinder appear to be the same size as viewed by eye.  Whilst arranging the camera and lens it was interesting to see the point at which the images in both eyes came together as the sizes matched.  The shutter speed (1/80), aperture (f7.1) and ISO (200) were the same for all 3 photos

Photograph 1 - Focal Length 48mm Click here for full size

Photograph 2 was the wide-angle shot, which shows approximately 40% more of the scene compared to the standard photograph.  This dramatically changes the framing of the image and starts to introduce some distortion of the image towards the edges.

Photograph 2 - Focal Length 18mm Click here for full size

The third photograph was the telephoto one, which only shows a small part of the scene compared to the standard photograph and distances appear shortened

Photograph 3 - Focal Length 200mm Click here for full size

The next stage of the exercise was to print each image out on A4 paper and return to the spot where the photographs were taken.  Then I held them up in front of myself and moved them until the objects on the paper appeared the same size as the real scene.

The standard print was by far the easiest to view, as the sizes matched at just under arms length at about 60 centimeters from my eyes.  Viewing felt quite natural with this image.


I couldn't match the sizes with the telephoto print as my arms weren't long enough and even at full stretch it was far too close.

The wide-angle print ended up about 6 centimeters from my eyes when the size of the objects matched, which didn't make for easy viewing.

I learnt from this exercise the relation between focal length compaired to what we see naturally.  This gives real world meaning to focal lengths and will undoubtedly help with lens choice, composition and imaging how a photograph of any scene could appear.

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