Focus.

Exercise: Focus with a set aperture
For this exercise I found a scene which presented three subjects at varying distances from the camera. I used a fixed focal length lens and selected an aperture of f1.4 to highlight the effects of different points of focus.

For Photograph 1 I focused on the tree nearest the camera.

Photograph 1. 30mm @ f1.4

In this picture the attention is immediately drawn to the detail of the tree to right of the frame. The rest of the image has been thrown out of focus by a combination of the wide aperture and the proximity of the point of focus to the camera lens.

For photograph 2 I set the focus on the tree to the left of centre.

Photograph 2. 30mm @ f1.4

Now the attention of the viewer has been moved away from the tree in the foreground which appears blurred and lacking in detail. The point of focus has moved to the tree to the left of centre. However, despite the aperture remaining at f1.4, the area of sharpness within the picture appears to extend deeper into the image. I believe this is due to the point of focus being farther away from the camera than in photograph 1.

For photograph 3 I focused on the distant tree in the centre of the frame.

Photograph 3. 30mm @ f1.4

The tree in the foreground appears to be even more blurred than in photograph 2. The middle tree to the left of centre has lost some sharpness but still retains an amount of detail despite the widest aperture being set. The trees at the back of the image are more detailed now.

Of the three images here, I prefer photograph 2. The point of focus on the tree to the left of centre immediately draws your attention to it, and the way the tree is leaning to the right then gently takes your eyes to the trees at the back of the frame.



Exercise: Focus at different apertures.
I set up a scene indoors for this exercise, using just the ceiling light. I lined up a row of model cars, deliberately placing the car with the strongest colour in the centre and using it as my point of focus. With my camera mounted on a tripod I selected my widest aperture and the appropriate shutter speed and took Photograph 1

Photograph 1. 1/60sec @ f1.4

With the aperture wide open the depth of field is very shallow. The limit of sharpness really only covers the car in the centre of the line up with the models at either end being completely out of focus.

I then adjusted the aperture to a mid setting and applied the necessary shutter speed for photograph 2.

Photograph 2. 1/2sec @ f8

With the aperture stopped down to f8 there is now clearer detail in more of the image as the limit of sharpness has increased to cover the models either side of the centre car. Additionally the cars at either end of the row, while still out of focus, are significantly sharper than they appeared in photograph 1.

Now I set the aperture to it's minimum setting of f16 before taking photograph 3.

Photograph 3. 2secs @ f16

In this photograph the limit of sharpness has extended almost to the edges of the frame. All the models now seem reasonably sharp although the outside cars still appear a little soft. Stopping down to the minimum aperture brings most of the frame into focus but at the expense of having to use a longer shutter speed as clearly demonstrated here with an exposure of two seconds.

Getting to know your camera. Focal length and angle of view.

Project: Getting to know your camera

The reason I enrolled on The Art Of Photography was simply to improve my image making technique and ability. In order to achieve this it made perfect sense to refresh my knowledge of how to actually operate my camera. A couple of hours spent sat down with my manual and camera to hand was time well spent. Indeed it was somewhat refreshing to discover one or two elements of operation hitherto unknown to me. I plan to revisit my manual in six months, to ensure retention of knowledge. Of course a camera is nothing without a lens. Lenses for DSLR cameras are available in a number of focal lengths from wide-angle to telephoto, offering various angles of view.

Exercise: Focal length and angle of view
I selected a place with which I was familiar and which offered content I considered useful for the purpose of this exercise. I made a note of the exact spot at which I set up the tripod.  I adjusted my short zoom lens so that the image seen in the viewfinder was approximately equal to the view from my unaided eye. This, somewhat surprisingly, gave me a focal length of almost exactly 50mm. I was expecting a much shorter focal length, around the 32mm mark. I took photograph 1.

Photograph 1 @50mm

This is fairly representative of the view seen with the naked eye, not allowing for peripheral vision. We can see an expanse of buildings with the river in the foreground. Everything appears to be in order, from the flat barge, to the larger, higher wall, then the larger still three storey building and finally on to the skyscrapers.


I then set the focal length of my lens to 17mm and took Photograph 2.

Photograph 2 @17mm

Now the angle of view has changed dramatically. Much more of the river in the foreground can be seen and the expanse of buildings look much farther away than they actually are. There are  more buildings visible to the left and right and further objects have appeared in the foreground, specifically the stern of the ship to the right. This actually appears to be larger than the skyscrapers as the short focal length has altered the perspective.

For the next image I replaced my standard zoom lens with a telephoto zoom and selected a focal length of 270mm, then took photograph 3

Photograph 3 @270mm

With the aid of the telephoto focal length the scene now seems very much closer. There is no sign of the river in the foreground and the objects we can see are barely perceptible at the17mm focal length. In addition to this, the buildings also look closer to each other than they actually are, a result of the image being "compressed" by the increased focal length. We now only have the centre of the original frame visible to us and this is shown with much greater detail than in the previous two photographs.

I returned a few days later with prints of the photographs in hand. I held out photograph 1 and discovered that I had to hold this at arms length to fit it into the scene before me. When I held photograph 2 up and fitted it into the scene, it was actually blurred because it was so close to my eyes. No more than about eight inches away. I couldn't hold photograph 3 far enough away for it to fit into the scene. I estimate it would have been about fifty inches away from me.

This exercise has demonstrated the effects brought about by changes in focal length. At one end of the scale, 17mm wide-angle, not only do we have a wider angle of view, the main subject of the composition appears to be much farther away from us than it actually is.  At the telephoto end of the scale the subject has been drawn much closer to us. Additionally, any distance between the subjects viewed through a telephoto lens appears to be reduced.