Saturday, December 16, 2017

What Is Depth of Field?

The world of photography is more than just going to exotic places and pressing the shutter button. If that’s the case, any girl with her mother’s latest smartphone would brag about being a photographer. Using the most expensive camera setup in the world also does not guarantee that your pictures will look good on Instagram and Facebook. In reality there is a big difference between “just another photo” and “well-captured photo” because more often than not the latter is taken by someone who has better knowledge about how camera works than the girl. One of the most important terminologies to understand is Depth of Field. And if you think that Depth of Field literally means how deep the field is, well then you are wrong.

In photography, depth of field is a zone within which an object in a photo appears in focus. There are only two Depth of Field zones:

  • Shallow: a small portion of the photo appears in focus
  • Deep: almost everything in the photo looks sharp

Capturing a photograph with shallow depth of field should produce something called bokeh effect – it is not a misspelled as you may think, the name really is bokeh. It is most often used in portraits and wildlife photography, but you can try it for selfies and food photography too.

Achieving Depth of Field for Bokeh Effect

In contrast to what you believe, a camera (or more specifically a lens) can only focus at one “point” only. Just because your camera says it has “multiple focus points” feature, it does not mean the camera can actually focus on many different points in a single frame. This is either technically impossible or the technology is just not there yet. In the event you figure out how a lens can make this possible, the patent office will be happy to welcome you. However, a camera can indeed focus at multiple objects as long as they are at roughly the same distance from it so the objects are within acceptable depth of field.

For example during a scuba diving activity with a buddy, you want to have an underwater bokeh photograph as something to show-off on the Internet. Because you think it is a brilliant idea to include an Orca in the frame, your friend must wait a little bit longer for the Orca, which currently is swimming right behind you at speed, to come a little bit closer. That way, your buddy can get the focus right; otherwise, the Orca may look blurry and no one back home has evidence of how your life ended. Since the wide-open jaws of the Killer Whale is pretty close to your head, both objects can look sharp while everything else behind appears blurry.

What Is Depth of Field
Sometimes the line between Depth of Field and blurriness is well, blurry
Some cameras have built-in “bokeh effect” feature, which means you don’t have to adjust the aperture and distance to the object to get the shallow depth of field. In most (if not all) cases, all these automatic adjustments are done digitally by the camera software – yes, a camera also has a software that you can update. The problem is that digital adjustments can look quite foolish among photographers, so unfortunately you will still have to learn about some camera settings and read user manual, or you can just lie about it.

Aperture is an opening or hole through which light travels to the image sensor. Larger aperture means the sensor receives more light, and smaller aperture brings is less light. Aperture in your camera is calibrated in f/stops and measured in numbers such as 1.4, 2, 2.8, 3.5, 11, 16, and some others. Two things to remember:

  • Higher f/stop – narrower opening – greater depth of field – sharp background

  • Smaller f/stop – larger opening – shallower depth of field – blurry background

It may sound contradictory that smaller number corresponds to larger opening, mostly because it is indeed contradictory so the problem is not on you; don’t ask your mother to have your brain examined just yet.

Omitting all the explanations about the witchcrafts that happen inside the camera, you need wide aperture and close focusing distance to achieve greater depth of field and get the bokeh effect. Therefore by adjusting the aperture setting on the camera to the smaller number, you can get the desired blurry background. As you scroll through the numbers, the Shutter Speed will also change accordingly. With large light opening, the shutter does not have to stay open as long to capture the image with the right exposure; this translates to faster shutter speed.

Distance between the object and lens also matters. As a rule of thumb, you want the object to be as close as possible to maintain focus but keep the background slightly far behind it. With wide aperture, the camera should focus almost entirely on the main object without picking up details of the surrounding.

Manual Focus

Of course it is easier to achieve if you also use manual focusing; this way you decide which part of the frame looks the sharpest. Turning the focus ring allows you to at least have a preview of what the end result should be; if your camera or lens does not have this manual option, you are stuck with automatic focus option so you may need to move forward and backward until you find the perfect distance for nice depth of field.

Aperture Mode

Since you are beginner in photography and reluctant to mess around too much with manual setting, there is an easy way to get bokeh effect: Aperture Mode - of course you're beginner in photography; otherwise you won’t be reading this.

A DSLR has something called PASM (Program, Aperture Priority, Shutter Priority, and Manual) options. For a nice depth of field, turn the camera into Aperture Priority so you can adjust the f/stops. Other functions such as shutter speed will be automatically configured by the camera. Use the lowest possible f/stop number (larger opening) and experience with object distance. In Point-and-Shoot camera where there are no PASM and bokeh effect options, your best chance of getting shallow depth of field is by using the Portrait Mode; it may not be the best and it also takes more walking back and forth, but it is workable and at least you burn some calories.