I decided to start a blog series on photographic terminology and this post is the first in this series. Photography is a blend of art and technology. I believe that Art and Technology are interdependent. While Art inspires innovation in technology as a means, technology enables one to express artistic abilities.
When I first bought my camera, I wanted to know how these things work. I wanted to know everything about the sensors, camera controls, lenses and such stuff. It is not a surprising thing if you find yourself with similar thirst. In fact some of the most successful photographers suggest us to know our gear better in order to take better pictures. On the other hand, I was not able to suppress that thirst for knowing the nuts-and-bolts of photography.
Regarding photography, there is a lot of technology involved in the modern DSLRs and the lenses. The modern day DSLR is similar to any old film SLR with few differences in the hardware and the operating software under the conver. The heart of a film SLR is the film and in a DSLR it is an image sensor. (more on sensors in a different post)
Ok, lets come to the point - what is depth of field in Photography? The straight answer is - depth of field is the area in the photograph which is in the acceptable range of sharpness. Suppose you are taking a photograph of a field where there is a tree in the middle. If you point your camera and focus on the tree and take a picture, in the resulting image, you can see that not only the picture is sharp but few inches/feet before the tree and few feet/inches behind the tree is also sharp. This band of area which is in sharp focus is called depth of field. The below pictograph can help in understanding this
|--out of focus--|----focused---|-----out of focus-------|
Ok, then how to control this depth of field for creative purposes? That't the crux of the matter.
Depth of field highly depends on the aperture of the lens (lens opening) and the focal length of the lens.
Focal length: The wide angle lenses are known for their huge depth of field. For e.g: SMC Pentax DA 12-24mm. The longer the focal length the thinner the depth of field becomes. On my SMC Pentax FA 100-300mm f4.7-5.6 lens, I need to use f8-f16 for acceptable depth of field when shooting tiny birds. At times the depth of field can get razor thin with this lens. On the other hand on my SMC Pentax DA 16-45mm f4 lens, I hardly see any out of focus areas unless the subject is close.
Aperture: Aperture is the opening of the lens. The bigger this opening (means small f numbers like f1.4, f1.7 etc) the thinner the depth of field, the smaller the opening (means bug f numbers like f11, f16...etc) the bigger the depth of field. This phenomena is purely optical rather than any gimmick by the sensor or film. Ansel Adams explains this in his book 'The Negative'.
Pictures demonstrating this will be added later.
There are different contexts where a thinner depth of field is desired and where a huge depth of field is desired. For example, if you are taking the portrait of a family member on a busy street, you do not want to have all the moving people distracting the viewer of the photography. So the subject should be isolated and the rest (foreground and background) should be blurred. In order to achieve this on a given lens you need to choose the widest aperture, like f 1.4, f 2.6 till f5.6 is acceptable. The lens choice could be a medium telephoto lens around 70-150mm range.
Shooting landscape demands huge depth of field, putting everything in focus. This can be achieved only through a wide angle lens with the smallest aperture possible. The added photos demonstrate this effect.
Based on the need, the lens choice and the aperture setting influences the depth of field in photography.
When I first bought my camera, I wanted to know how these things work. I wanted to know everything about the sensors, camera controls, lenses and such stuff. It is not a surprising thing if you find yourself with similar thirst. In fact some of the most successful photographers suggest us to know our gear better in order to take better pictures. On the other hand, I was not able to suppress that thirst for knowing the nuts-and-bolts of photography.
Regarding photography, there is a lot of technology involved in the modern DSLRs and the lenses. The modern day DSLR is similar to any old film SLR with few differences in the hardware and the operating software under the conver. The heart of a film SLR is the film and in a DSLR it is an image sensor. (more on sensors in a different post)
Ok, lets come to the point - what is depth of field in Photography? The straight answer is - depth of field is the area in the photograph which is in the acceptable range of sharpness. Suppose you are taking a photograph of a field where there is a tree in the middle. If you point your camera and focus on the tree and take a picture, in the resulting image, you can see that not only the picture is sharp but few inches/feet before the tree and few feet/inches behind the tree is also sharp. This band of area which is in sharp focus is called depth of field. The below pictograph can help in understanding this
|--out of focus--|----focused---|-----out of focus-------|
Ok, then how to control this depth of field for creative purposes? That't the crux of the matter.
Depth of field highly depends on the aperture of the lens (lens opening) and the focal length of the lens.
Focal length: The wide angle lenses are known for their huge depth of field. For e.g: SMC Pentax DA 12-24mm. The longer the focal length the thinner the depth of field becomes. On my SMC Pentax FA 100-300mm f4.7-5.6 lens, I need to use f8-f16 for acceptable depth of field when shooting tiny birds. At times the depth of field can get razor thin with this lens. On the other hand on my SMC Pentax DA 16-45mm f4 lens, I hardly see any out of focus areas unless the subject is close.
Aperture: Aperture is the opening of the lens. The bigger this opening (means small f numbers like f1.4, f1.7 etc) the thinner the depth of field, the smaller the opening (means bug f numbers like f11, f16...etc) the bigger the depth of field. This phenomena is purely optical rather than any gimmick by the sensor or film. Ansel Adams explains this in his book 'The Negative'.
Pictures demonstrating this will be added later.
There are different contexts where a thinner depth of field is desired and where a huge depth of field is desired. For example, if you are taking the portrait of a family member on a busy street, you do not want to have all the moving people distracting the viewer of the photography. So the subject should be isolated and the rest (foreground and background) should be blurred. In order to achieve this on a given lens you need to choose the widest aperture, like f 1.4, f 2.6 till f5.6 is acceptable. The lens choice could be a medium telephoto lens around 70-150mm range.
Shooting landscape demands huge depth of field, putting everything in focus. This can be achieved only through a wide angle lens with the smallest aperture possible. The added photos demonstrate this effect.
Based on the need, the lens choice and the aperture setting influences the depth of field in photography.
lens. I was expecting to capture landscapes and little did I know that I end up taking lot of portraits, for which the lens is not so suited. By the time we came back to the cottage, there were 130 photos and most of them were portraits. ;-)
