Project; Camera – Focus; Exercise 2, Set Aperture

The choice of where to place the focal plane and the depth of field chosen to the back and front of the focal plane are the subjects of Exercises 2 and 3 of the Art of Photography course and are dealt with this and an accompanying blog (http://wp.me/p3PbRS-E).

Focus – Set Aperture

Stephen Shore in The Nature of Photographs – a core text for the course – refers to the fact that a camera ‘…creates a hierarchy in the depictive space  by defining a single plane of focus..’.  he further notes that this ‘… gives emphasis to part of the picture and helps to distill a photograph’s subject from its content.’  The only way to reduce the plane of hierarchy is to photograph a flat subject that is itself parallel to the picture plane.  Shore provides the example of Brassai’s Graffiti from c. 1935 to illustrate his point.  In all other cases the choice of focal point (plane) by definition sets up a hierarchy of interest.  Good examples of selecting a particular focal plane and then ensuring that the main point of interest is identified through sharp focus are recent images from Alex Wong  of Michelle and Barack Obama at the Martin Luther King 50th celebrations in which the couple are shown sharply focused against a back drop of an out of focus Lincoln.  The url below leads to one of these images.

Three images were produced for the exercise to demonstrate the impact of selectively focusing on a particular part of the image while maintaining a set aperture.  These three images show clearly the effect of focusing near, middle and distance.  The lens was a 60mm (EFL 90mm) with a shutter speed of 1/200 and the aperture set at f2.8 to ensure a narrow depth of field.

Near Distance Focus

Middle Distance Focus

Far Distance Focus

It is very clear in these instances how the eye is drawn to the point of focus. I have no particular preference for the style of these images based on selection of focal plane other than to note I feel I have to ‘work’ somewhat harder to read the image in which the focal plane is furthest away.  This may be because of the choice of subject which, in hindsight, does not lend itself to the eye being drawn to the distance.  Perhaps if the choice of subject was more clearly defined to begin with (like the images used by Michael Freeman in The Photographer’s Eye to illustrate the point (p 94)) then the issue of where my eye was drawn to most easily would have been clearer.  Freeman notes, just like Shore, that sharp focus, de facto, ensures the point of attention but adds that deliberate (and unexpected) use of out focus works well because it flouts established procedure.

Back to Shore who raises the possibility of having the focal plane running perpendicular to the picture plane.   He shows that by using a traditional view camera with a flexible lens the focal plane can be changed to run perpendicular .  He chooses for illustrative purposes an untitled image from Jan Groover from 1985 (p 87 – in The Nature of Photographs).  Also of interest here is  recent development in focusing technology offered by the Lytro camera which allows post shutter release adjustment of focus thus providing an opportunity to change the focal plane after the image has been taken.

Michelle and Barack Obama image from Martin Luther King 50th Anniversary.

http://news.yahoo.com/lightbox/president-barack-obama-first-lady-michelle-obama-arrive-photo-190118033.html

Project; Camera – Focus; Exercise 3, Different Apertures

The choice of where to place the focal plane and the depth of field chosen to the back and front of the focal plane are the subjects of Exercises 2 and 3 of the Art of Photography course and are dealt with this and an accompanying blog (http://wp.me/p3PbRS-z).

Focus – Different Apertures

By selecting differing apertures the depth of field (amount of focus in front of and behind) the focal plane can be increased or decreased.  Wide apertures (small f numbers) give a very narrow depth of field whereas narrow apertures (large f numbers) give a much greater depth of field.  Choice of aperture is therefore a creative choice; narrow depth of field/wide aperture will ensure that attention is drawn to a particular focal plane whereas narrow aperture/narrow depth of field allows the eye, as Bruce Barnbaum in  The Art of Photography, (rockynook, 2012) notes, ‘…to peruse the scene and get information out of every part of it..,’ (p46).    There are technical issues associated with depth of field.  First, depth of field is 1/3 in front of the focal plane and 2/3 behind.  In practice this means that if sharpness throughout the image is required the focus point should be 1/3 into the image.  Second, as apertures decrease sharpness of focus decreases so that at very small apertures images are not quite as sharp as they are at  wider apertures.

For the exercise, three images of the keys of a piano were captured at f2.8, f11 and f22 to illustrate the effect of closing down the aperture on depth of field.  The f2.8 aperture clearly shows the narrow depth of field in the middle of the image. The effect of narrowing aperture to f11 and f22 is not quite so pronounced but still noticeable in comparison to the f2.8 image.

f2.8

f11

f22

A variant on the exercise is provided by the two images below (captured as part of an exercise in a short creative photography course I took several yearsg ago) in which the nearest object is the point of focus.  The image designated f5 shows clearly that the nearest object is in focus while narrowing the aperture to f32 brings the two distant images into focus.

f5

f32

The effect then of opening or closing aperture is clear, from a technical viewpoint; narrow apertures give large depths of field while open apertures give shallow depths of field.  Just as with focal point in the accompanying blog (see above) so to with depth of field in the these exercises; I am neither drawn or not to particular results.  However, unlike the images in the accompanying blog where I had a slight preference for near focus, perhaps because of subject choice, I see the choice of depth of field as purely a creative decision.

What then of the creative decisions surrounding depth of field?  Bruce Barnbaum’s position above is clear; narrow depth of field provides an image that allows the eye to peruse and obtain information from the whole scene.  Barnbaum’s slit canyon images (see http://www.afterimagegallery.com/barnbaumconvergence.htm for an example of such an image) are very good examples of images with immense depth of field which draw the eye over the whole scene.

In contrast, P. H. Emerson’s  During the Reed Harvest, (1886) (see page 83, Stephen Shore, The Nature of Photographs) shows clearly the effect of having a shallow depth of field and its effect on  the viewers focus of attention – quite clearly the focus is on the nearest three reed harvesters and progressively less attention to the fourth further away and boat in the middle distance.

So, depth of field, while primarily a technical feature of the camera and its aperture setting offers creative possibilities in the context of focusing, or not, attention to a particular point within the image.