Posted by M.Kumar at 5 June , 2009

In continuation to Understanding Shooting Modes (Part-I) where I described the Auto and Programmed Modes, I’ll explain and illustrate one of the advanced modes called Aperture Priority Mode in this part.

Aperture Priority Mode

This mode lets you choose the aperture (lens opening) and the camera chooses the appropriate shutter speed for proper exposure.

Just like human’s eyes, lens of a camera has an opening called iris that opens and closes according to automatic or manual settings. This in optical terms also referred as “Aperture”. Changing the aperture settings changes the size of the opening which controls the amount of light the lens passes through to the image sensor.

Why to use Aperture Priority Mode?

This mode is used when you want to have control over depth-of-field. This is measured in f-stops i.e. f/1.4, f/1.8, etc. Higher f-stop numbers indicate smaller aperture and vice-versa.

The “f-number” is the ratio of distance from the sensor/ film to the optical center of the lens in your camera. When you buy a lens for your camera, it will have a number on it, something like 18mm, 55mm, 105mm, etc. These numbers are called as focal length.

To put all of this simple, when the aperture of a 200mm lens (focal length) is 50 mm (aperture opening) wide, your f-stop will be f/4, because the ratio of 200/50 equals four. If you “stop down” your aperture to half that size – 25 mm wide – your f-stop will be f/8. (200 divided by 25.) So the “f-number” gets larger as you let in less light.

What is Depth-of-Field?

Depth-of-Field is the distance between the closest sharply focused object to the lens and the farthest sharply focused object from the lens. Large apertures (lower f-stop) create shallow depth-of-field and the smaller apertures (higher f-stop) create greater depth of field.

This is a bit confusing. But I learned it using an example of 10 trees standing in a row. Lower f-stops will capture lower number of trees and higher f-stop will capture more numbers of trees.

More Light <<

f/2

f/2.8

f/4

f/5.6

f/8

f/11

>> Less Light

Try it

Visit some nearby garden where you can locate a flower and experiment the following:

Shallow Depth-of-Field

1. Turn your camera’s exposure mode dial to Aperture Priority.
2. Lower down the aperture to f2.
3. Focus the flower and press shutter release button.

Result The lower f number will generate a shallow depth of field, thus focusing only the flower, not the background.

Greater Depth-of-Field

1. Turn your camera’s exposure mode dial to Aperture Priority.
2. Lower down the aperture to f22.
3. Focus the flower and press shutter release button.

Result The higher f number will generate a larger depth of field, thus focusing everything along with the background.

Please leave a comment so as to let me know that this post is at least helping some one

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Tags: Aperture, Aperture Priority, Auto Mode, Camera, Depth Of Field, DOF, DSLR, EXIF, Exposure, f-stops, f/11, f/2, f/2.8, f/4, f/8, Focal Length, Image Sensor, iris, ISO, Landsacpe, Lens, Macro, motion, Night, Photography, Point-and-shoot, Programmed Mode, Protrait, Shallow Depth-of-field, Shooting Modes, Shutter, Shutter Priority, sports, tripod
Posted in: Photography , Understanding Shooting Modes