Why Is The Concept of Depth Of Field So Elusive?     

depth-of-field-2

d-of-f-1a

d-of-f-2a

 

The topic of Depth of Field just keeps coming up and I suppose it deserves a revisit for this year. There must be a reason why Depth of Field is so elusive to photographers.

I wonder if it is because modern cameras have computers that focus, balance the colour, and control the exposure. All are impressive functions that make new users believe all they need to get a good photo is to point and shoot.

I have discussed Depth of Field in my blog numerous times. And find myself constantly explaining how depth of field works to photographers that visit my shop. I must admit that many photographers just smile and nod like they understand what I am talking about. However, unfortunately, when I see their photographs I realize otherwise, and I expect most would have been much happier if I just told them the reason their picture wasn’t really sharp was because they needed a new lens. (Buying a new lens is so much easier than taking a class in photography.)

Understanding of the concept (and I guess technique) of depth of field will make their photographs better and save them money, as they did not really need a new lens.

This past week, I viewed an image a photographer posted online. He wrote that he was proud with his creative and unusual view. The overall exposure was fairly good, the colours were close to reality, and the centre of the picture was in focus. Nevertheless, other than that small, in-focus, central area the rest of his subject wasn’t in focus at all. The foreground was blurry and the background was blurry.

The definition of depth of field is, “that area around the main subject, in front of and behind, that is in acceptably sharp focus”. In application the wider the lens’ aperture is the less the depth of field, or that area of sharp focus, around the main subject will be. Practically, the depth of the field of focus will be 1/3rd in front and 2/3rds behind the subject.

Using a wide aperture can increase the exposure in limited lighting conditions; but, along with the benefit of additional light reaching the camera’s sensor, the resulting effect is reduced depth of field. Creating a field of focus behind the subject of 4 inches or so might look really good when making a portrait, but it is not effective in a scenic.

The smaller the lens aperture the more the area of focus around the subject will be. I prefer using a small aperture for scenic photography. I am concerned with all elements in the photograph, front to back, of being sharp and in “acceptably sharp focus”.

The Internet is packed with information on scenic photography, and there are thousands (millions?) of books on photography that are easy to read. I expect that any discussion on scenic photography will include a full discussion of Depth of Field.

Depth of Field

I have included a few examples that show the technique.

I have included a few examples that show control over the technique.

D of F 2

hoodo and fence 3

Plowing the field

Shoot'n the sunrise 1

A smaller aperture for more depth of field.

Shoot'n the sunrise 2

A wider aperture for less depth of field.

Heron

Blue Freighter Frog

Brewster copy 2

Truck in the meadow copy

River Sandon BC

 

A topic that I recently discussed in my classes, that I repeatedly explain to photographers that come to my shop complaining about what they believe are lens focusing problems, and have written more than once about is “depth-of-field”, but it still seems to be an elusive concept for many. However, it is really important and photographers should make the effort to grasp it even though it appears difficult.

I pondered this last Thursday when a local photographer showed me an image she had made during a wedding. She showed it to me proudly and commented that she has chosen that lens because it let in more light when photographing in low light, but complained that the expensive lens she had didn’t seem all that sharp.

The image showed a view of the central aisle of the church with pews left and right, leading up to the bride in the distant centre, approximately 20 feet from where the photographer was standing. The overall exposure shot at an aperture of f/2.8 was fairly good. However, what that photographer saw was the lack of sharpness everywhere, except for the bride standing in the aisle.

The definition of depth-of-field is “that area around the main subject, in front of, and behind it, that is in acceptably sharp focus”. In application the wider the lens’ aperture is set the less will be the depth of field, or that area of sharp focus, around the main subject will be.

Wide aperture lenses are very popular these days and using a lens at a wide aperture like f/2.8 when making a portrait isolates the main subject and produces a soft, out-of-focus background referred to as bokeh by reducing the depth of field. Bokeh is a pleasing soft blur produced by a wide aperture lens in the out-of-focus area directly behind the subject.

In this instance the photographer was relying on the wide aperture to increase the exposure in limited lighting conditions. That additional light allowed a faster shutterspeed for handholding, but along with the benefit of additional light reaching the camera’s sensor the resulting effect was to reduce depth of field.

Using that wide aperture created a field of focus in front of the subject of a couple feet and only a bit more behind that would be fine in a portrait, however in that photograph of the church aisle with pews on both sides, that included lots in the foreground and much of the background, looked out-of-focus.

Many photographers unwittingly rely too much on their photography equipment to (magically?) make good images, and blame faults in their photographs on that same equipment. Understanding the basic concept of depth-of-field would have made that photograph more to the photographer’s liking.

The smaller the lens aperture number is the less the depth-of-field. I prefer using a small aperture (larger number) for scenic photography and, as in this instance, interiors. The answer to that photographer’s low light problem would be to increase the ISO and use a smaller aperture. (I would be surprised to find a modern DSLR that wouldn’t shoot noise free at ISO1600 or even more)

Assuming the lens isn’t sharp when the real problem is with photographic technique is expensive if the photographer goes so far as to replacing a lens. My recommendation is to spend time learning the basics of depth of field instead of blaming equipment when problems occur.

 

I appreciate reader’s comments. Thanks, John

My website is at www.enmanscamera.com

The basics of photography and depth of field

One topic that I have discussed during many classes that I instruct, and defined to many people that have come to my shop when they think they have are lens or focus problems, and more than once written about is “depth of field”, but it still seems to be an elusive concept for many. 

 I pondered about this last Thursday when a local photographer showed me an 8×10 print from photographs he had made inside a church during a wedding the previous weekend.  He showed it to me proudly, but commented he wished that his lens was sharper at its wide-angle focal length.

 The print displayed a view down the central isle with church pews left and right, leading to a pulpit in the distant centre, likely about 30 feet from where the photographer was standing.  The overall exposure was fairly good, and he told me he had shot at an aperture of f/2.8.  However, the fact that his photograph wasn’t in focus, except for the pulpit, had very little to do with using his zoom lens at its wide-angle focal length.

 The definition of depth of field is “that area around the main subject, in front of and behind, that is in acceptably sharp focus”.  In application the wider the lens’ aperture is the less the depth of field, or that area of sharp focus, around the main subject will be.

 Wide aperture lenses are very popular these days and using a lens at a wide aperture like f/2.8 when making a portrait isolates the main subject and produces a soft, out-of-focus background by reducing the depth of field.

 Using a wide aperture can increase the exposure in limited lighting conditions, but along with the benefit of additional light reaching the camera’s sensor the resulting effect is reduced depth of field.  Creating a field of focus behind the subject of twelve inches or so might look really good when making a portrait, but in that photograph of the church isle with pews on both sides and the distant pulpit, everything in the foreground, from the photographer to the pulpit, looked out-of-focus.

 Many photographers unwittingly rely too much on their photography equipment to (magically?) make good images and blame faults in their photographs on that same equipment. Understanding the basic concept of depth of field would have made that photograph work easily. 

 I have photographed weddings in that same church and instead of relying on a wide aperture to bring the necessary light into the dim environment, I use a flash and an aperture opening that will give me lots of depth of field so the foreground as well as the background will have reasonable sharpness.

 Yes, subjects closer to the flash will be brighter and those further away will be darker, but I use an off-camera flash cord and hold the flash at arms-length above my head, and direct the light over and above the closer pews and onto more distant subjects. With film this technique is more hit and miss, but with digital technology I just check the camera’s LCD (liquid crystal display) and make any light intensity corrections on the flash menu. I can also make further corrections to the image in seconds in postproduction using PhotoShop.

 The smaller the lenses aperture is the more the area of focus, or depth of field, will be.  I prefer using a small aperture for scenic photography and, as in this instance, interiors.  In both types of photographs I am concerned with all elements in the photograph, front to back, of being sharp and in “acceptably sharp focus”.

 Assuming the lens isn’t sharp when the real problem is with photographic technique can get expensive if the photographer goes so far as replacing a lens. My recommendation is to spend time learning the basics of photography like depth of field instead of blaming equipment when problems occur.

 http://enmanscamera.com