Focus

To record the image the camera is used to project the light from the object onto the film/senor surface, this is achieved by the use of a lens which allows the image to be focused on to the film surface.The lens has the ability to reproduce the image in a variety of magnifications; this is known as “focal length”. The focal length of the lens is the distance from the rear of the lens element to the film plane, when the lens is focused on infinity. There are two main effects of varying focal lengths of a lens, magnification and angle of view. The more magnification of an image on the film, the greater the focal length of the lens which means that the further away the lens is to the film, the less magnification required the closer the lens is to the film plane. There is also variation in angles of view and perspective. The more magnified decreases the angle available to view of the image; it also compresses the image so objects appear closer together and so alters the perspective of the image.

EXERCISE

Take a series of images at the same aperture and shutter speed ( f5.6 1/60s) and alter the points of focus manually

2 to 3 images


FOCUS WITH SET APERTURE




The first image shows the focal point as being the centre of the image of the red apple. As the aperture is wide this means that the depth of field is shallow which means the area of sharpness will be weaker from the point of focus. This means that the foreground and background of this picture is not sharp.
















In this image the point of focus is the first apple. This means that the centre of the image and the background are not sharp.






























The final image point of focus this the apple in the background. this means that the foreground and centre of the image is not sharp.

OUTCOME

Exercise shows the variation of depth of field when focusing on different points. Note the change in focus between the foreground and back ground

LEARNING NOTES/COMMENTS
experiment with aperture within composition for created effect

As shown in previously focal lenght can be altered by changing the level size of the apeture and therfore altering the depth of filed and can be used to to isolate objects against the background.