Wednesday, April 27, 2011

Depth Of Field

This is one of my favorite terms in photography because the basic theory applies to so much of life. I haven’t written about anything photographic in a while and began a crash course on photography some weeks back. So here is the second term photographers need to know in making a creative choice when using their cameras. Last time I talked about apertures and shutter. The aperture controls the depth of field in an image. The basic concept is the elements of the images that are in focus from the front of the subject to the back of the subject. For instance a landscape image has a greater depth of field, (the foreground is as sharp as the background mountains in the distance) than a portrait (where only the subject or a particular feature of the subject is in focus and everything in front of or behind is a blur). Today’s close up image of Corey. His eye becomes the focus and the red cloth on his shoulder is just slightly blurred, because this image was more about Corey’s connection to me as I was taking the image and the viewer who will eventually see the image. The way the camera controls this is by how tight or open the aperture on the lens is set. On a lens this is measured by f/stops. You will often see numbers 2.8, 4, 5.6, 8, 11, 16, 22, and 32. Oddly enough, they work in reverse of what you would logically think. The smaller the number the wider the opening and the more light it lets into the camera and the larger the number the more restricted the light into the camera. Each increment lets in double the amount of light as the previous, this is known as full f/stops. So the way to think about this process is that if f/2.8 is wide open it lets a great deal of light in to be recorded in a instant. It would be like if we close our eyes and open them in a new location, that we have never been and we just glace at this environment for that quick instant what do we actually take in a see: most people just what’s in front of them. The plane of the depth of what we remember is very narrow. The aperture works the same. It will record a very narrow depth in the image. Whereas if we restrict down the opening f/32. It’s almost like squinting and you have to observe the scene longer to take in the environment. The longer you look the more information your brain records, therefore more detail in the image because a greater part of the image is in focus.

So how does this translate into the creative choice? You, as a photographer, need to look at your subject and evaluate what you think is important in the image. You tell the story of the subject by where you direct the focus. Two examples of portraits where you would use each: #1 You are taking a picture of someone at a National Park and you want to show that they are indeed at this park with the scenic background behind. You want as much depth and detail as possible so you want you use an f/32 setting (higher the number possible). #2 So now you are in an environment that has a lot of distractions but is not very interesting at all, so you really don’t want to show any of kind of place where the subject is, but you just want a really beautiful picture of the person to capture their expression. You would choose an f/2.8 (lower the number) to blur all that distracting detail out of the image, creating a very narrow depth of field. These are the extremes of most camera settings, now there are many stops in between that give you varying degrees of this effect so you can effectively place the focus exactly where you want it. I tend to use something in the middle where my images become focused on the subject and often hint at their environment. I match this to my style and the way I process information in my life and if you know me this is the way I think. I am a romantic, and have a dreamy fantasy quality to my style. I selectively make you look at what I want you to see in my images and take you on the emotional journey I have with my subjects by narrowing how you see the image in the end.

The next image of Corey draws you more into his gentle seductive nature as a whole; the beauty of his skin color contrasted with the red fabric. I used a wider aperture to draw the viewer out to see the over all impression, it become more about mood than connection. Yet I still blur the environment so the image becomes timeless, not connected to any particular place. Last time I talked about putting your camera in an aperture priority mode. This is the best way to learn it. In this mode you get to choose the aperture and the shutter automatically adjusts the expose for the near perfect exposure. So the next time you are out with your camera and you want to take a picture, stop for just a moment and ask, what is my original impulse to take this particular picture? Now ask you self, what is my subject and how do I want to record this subject? Is the environment important? Then begin to narrow your focus to what it is that drew you to take the image in the first place.



Anonymous said...

Thanks Terry, you are a great teacher. Very good and easy to understand explanations. Ramon

BDSpellman said...

I think that's the best explanation of the relationship between aperture and depth of field I've ever read (and I've read a lot of 'em).