Depth of field is affected by 3 factors:
- Focal length
- subject distance
A large depth of field, means most things are in focus from the foreground to the background distance and a narrow (or shallow) depth of field means only things within a specific distance from the camera will be in focus.
having a smaller hole to let light through means you get a bigger size aperture (f22), and will produce greater depth of field than say (f2.8) a smaller size of aperture. aperture is a measurement of how much light can be transmitted through, not a length measurement.
Aperture changes Depth of field
the image above was how i understood how aperture change affects the depth of field. as the number on your Fstop decreases more light is allowed through and therefore creates a shallow depth of field showing a blurred background with the focus area in focus.
My example of how Depth Of field can change
Left: 6109.jpg Right: 6110.jpg
the image on the left has an f-number of 1.8 and as i has to change the shutter speed accordingly the shutter speed i used was 1/320th of a second. using a 28mm lens which is a wide-angle lens. a good depth of field became of these camera setting as sown on the image on the left (6109.jpg) the background is blurred and the features of the image i wanted highlighting most and the viewers eyes to be drawn to, are in focus.
the image to the right, opposite to the left hand image is mostly all in focus but as always on images there is some depth of field in the background, the mid ground is mostly all in focus and the foreground is all in focus. the setting used on the right hand image (6110.jpg) were aperture 81.8 (f-number) and the shutter speed needed to be 1/15th of a second.
i am pleased with these images an i think they turned out well but when i was actually taking the photographs i had a problem with them being too exposed so i took the raw file (before saving as a JPEG to insert into my blog) and lowered the exposure just a little and the image turned out well, and i am proud of the end result.
here’s another example of me using depth of field but at a slightly different angle on it. here i have over the depth of field from one place to another by focussing on the foreground and then the background it has altered the appearance of these images and changed the depth of field.
in landscapes everything ‘should’ ideally be in focus.
usually by selecting the correct aperture and moving the point of focus to the hyperfocal distance it would be possible to make the entire scene into focus. to ensure that you have achieved a focussed and clear image throughout the whole photo the depth of field needs to extend from the foreground until the infinity of the photograph (the furthest point viewable). which means the hyper focal distance needs to be the point of focus in your landscape (or just image). the hyperfocal distance is a point where the point of focus will result in the whole entire scene being in the depth of field.
Focal Length affects DOF
focal length effects the general aesthetics of an image but also the depth of field.the shorter your focal length, the more depth of field you will have. A 20mm lens will have more depth of field than a 50mm and a 50mm lens will have more than a 100mm. With really short lenses like 4 mm you will have a much larger depth of field. With long lenses, like 400mm, you will have tiny depth of field.
Subject distance affects DOF
The closer you are to your subject, the less depth of field there will be. The further away you are, the more depth of field you will have.