Focal length and character

In order to make a comparison of focal lengths, a simple head and shoulders portrait would seem to be all that is required. I therefore used the opportunity of a visit to a small church to take photographs of my wife at differing focal lengths.

Image 1: Short focal length (full frame equivalent to 27mm)

Nikon 18-200mm at 18mm: Iso 400 f6.3 for 1/30th seconds

Image 2: Mid-range focal length (full frame equivalent 72 mm)

Nikon 18-200mm at 48mm: Iso 400 f6.3 for 1/30th seconds

Image 3: Long focal length (full frame equivalent 300mm)

Nikon 18-200mm at 200 mm: Iso 400 f6.3 for 1/30th seconds

In image 1, the wide angle setting distorts her face, making her mouth, nose and glasses seem to bulge out unnaturally.

I found it difficult to identify any significant difference between image 2 and image 3, and her face appeared natural in both despite the significant difference in focal length and angle of view of the lens.

I was surprised by this. I would expect that the features closest to the camera would become less prominent at longer focal lengths. Taking rough measurements with a ruler, I compared the width of her features closest to the camera relative to the width of her face at the narrowest point which is further away from the camera. I found that there was the expected progression using the width of the frame of her glasses:

- Image 1, her glasses are 119% of the width of her face

- Image 2, her glasses are 112% of the width of her face

- Image 3, her glasses are 108% of the width of her face.

There is still some flattening of perspective in moving from image 2 to image 3, even though this effect was so subtle that it was not obvious to the naked eye.