LENS CHARACTERISTICS

The next sets of images serve to demonstrate different characteristics of camera lenses:

1. Lens-to-subject distance and its effect on perspective.

2. Effect of focal length compression on the scale of foreground and background objects.

FORESHORTENING

Purpose: To demonstrate how increasing the lens-to-subject distance affects perspective.

50mm (f8 1/200s ISO 400)

At approximately 6 feet, Greg appears normal.

24mm (f8 1/200s ISO 400).

At 3 feet all the lines seem to converge in the center of the image. Greg’s nose appears bigger with his forehead and chin receding unflatteringly.

My favorite image, by far, is the one taken at 128mm. While the 50mm one is a solid effort, it’s pretty bland with no photographic interest. The 24mm is just hideous and supremely unflattering. The 70mm was an improvement on the 50mm but I think the 128mm is the most flattering.

COMPRESSING PERSPECTIVE

Purpose: To demonstrate how increasing focal length compresses the scale between foreground and background objects.

Part 1 - Using a Foot Zoom

I couldn’t have chosen a trickier scene to photograph for this assignment. Besides the light changing constantly, there was also a 6 stop difference between the darkest area (the rocks) and the brightest (the grass), so I’ve decided to share my thinking and notebook with you.

For some reason I always feel like I should be able to calculate the right exposure quickly and on the spot, so when presented with conditions like I those in Concord on Saturday, there’s almost an immediate sense of mild panic. Truth is, there is no rush. Besides the light changing constantly, nothing was moving. There was no time pressure. In fact, this was the ideal moment to slow things down and really think about how I wanted to approach the scene.

Firstly, I drew a very rough representation of the actual scene in my notebook and then took light readings off the most important subjects in the scene. I used a spotmeter, but you can switch your camera’s exposure meter to spot and then point very precisely at different parts of the scene. You might want to zoom in to get the most accurate reading. I had already decided beforehand from where I was positioned under the tree, that I wanted f8 as my aperture and I realised that the only way I was going to get a shutter speed that would allow me to shoot this handheld (no lower than 1/15s) I had to push my ISO to 640. Using f8 and ISO 640 as the constant, I metered the different subjects to determine the corresponding shutter speeds.

I ended up with f8 1/800s when the cloud shifted and brightened the grass significantly, the rocks in the foreground gave me f8 1/13s which I rounded up to 1/15s.

With a 6 stop difference there was no way I was going to get both the grass and the rocks exposed adequately so I chose to expose more for the grassy area and to then lift the shadows of the rocks afterwards in Lightroom. I ended up shooting at f8 1/250. This represents a 2 stop over-exposure on the grass and a 4 stop under exposure on the rocks. In the days of film, you’d dodge and burn these areas to get the image you pre-visualized before shooting. By the way, this was also the reading (f8 1/250s) I got using an incident light meter in the bright part of the scene.

You can see the Before and After images below by moving the slider left and right. Also notice that I did these calculations in my notebook by physically drawing the shutter speed scale and moving the stops left and right.

What I’m hoping you’d see is how the rocks in the foreground and the house in the background, maintain approximately the same relative size and spatial relationship in all three photos. Even in the last image when the rocks seem really big in the foreground, the house in the background still appears to be at approximately the same distance from the rocks.

Part 2 - Using a zoom Lens

Notice how when you zoom in, all the objects in the image enlarge proportionately.

A couple of outtakes from the day. It really was the most glorious light once the clouds scuttled.