Lesson Two: Master Aperture

Lesson Two:  Depth of field & Aperture

·         Lens aperture controls depth of field.  Depth of field is the amount of distance between the nearest and the farthest objects in the picture.  In the following picture I used the depth of field to highlight my wedding bouquet. 

·         Lens aperture is the hole in the diaphragm of the lens that lets light into the camera.

·         Depth of field is caused by limitations of the human eye.  With a DSRL camera, the human eye will detect anything larger than 0.03mm in diameter as a blurred item .  Anything smaller than this will appear as a point instead of a circle and will appear sharp or in focus.

·         When a lens is focused it forms the light into a sharp point, focusing on what is closest to the lens.  Everything in the background is blurred, as seen in the following photo.  Although this is just a "weed", Queen Anne's Lace, It looks extra special when highlighted using aperture.

·         The eye is drawn to what is in focus and ignores the blurred items in a photograph.  Using lens aperture to adjust the depth of field helps the photographer to draw attention to the subject in a dramatic way.

·         The photographer can control the depth of field by adjusting the lens aperture. This can be done by making the hole in the diaphragm of the lens smaller.

·         For a landscape scene there should be sharpness in the foreground and the background.  In order to achieve this, the photographer should use a small aperture like f16 or f22.

·         For portraits, the subject should be the focus and the background should be blurred.   This can be achieved using a larger aperture value like f2.  This portrait of my son at a local park demonstrates how to highlight the subject rather than the background.  You know when you look at the picture that he is standing on a bridge , however your attention is drawn to him. 

·         The photographer should adjust the lens aperture to coincide with the shutter speed.  This is known as the law of Reciprocity.  The needs to increase when the shutter speed is faster;  more light equals less time.