Understanding Depth of Field0 When done well, a photograph that has good control over the depth of field can add dramatically to the impact of the picture.0 When we are talking about depth of field, what we are referring to is a shot were the main subject of the picture is in sharp focus but other elements in the picture are blurred or out of focus.
Understanding Depth of Field What do we mean by controlling depth of field (DoF)0 Two key terms to learn here are focal plane which is the area of the image that we want to have in sharp focus and bokeh which is the out of focus sections.0 This is the effect where the subject is in sharp focus but the rest of the image is slightly out of focus.0 The effect is referred to as bokeh. The more bokeh, the more dramatic the blurring effect.
Understanding Depth of Field Understanding Aperture0 If you have a fully automatic point and shoot then you will not be able to achieve the effect you want.0 Being able to control the depth of field is not very easy on lower end cameras as you need to be able to shoot in either an aperture priority mode or in a full manual mode.
Understanding ApertureDiagram of decreasing aperture sizes
Understanding Aperture0 The aperture setting is the size of the opening that is used to let light into the camera and onto the sensor.0 The size of the opening is measured is F-stops.0 The confusing part is that the larger the aperture setting, the smaller the hole that will be used to take the picture
Understanding Aperture0 The reason why lenses with a very large aperture (smaller f-stop number) are more expensive is because the lenses require more engineering and typically use better and more complicated lens elements.0 The other side effect of getting a lens with a small f-stop number is that the smaller the f-stop, the more light will come in per image thus allowing you to shoot in lower light conditions.0 A lens with a f/1.8 can shoot well exposed pictures in a situation that is much darker than an f/4.0 lens could shoot in.
Why Control DoF?0 The simple answer is mood.0 Quite often, the background of an image may be distracting from the subject matter, think of a bride standing in front of a wall of flowers.0 In this case, the bride is obviously the main subject and anything else may distract from the subject, by blurring out the flowers behind the bride, you can retain some of the color and texture without the detail, adding a much more dramatic feel to the image.
Choosing Lenses0 When choosing a new lens, once you decide once you decide the focal range you are looking for, then you go for the lens with the largest aperture (again, lowest number) that you can afford.0 A common misconception with new photographers is that a lens labeled with a single aperture will only do that aperture.0 The labeling denotes the maximum aperture at the listed focal length, So if you have a 70-300 f/4.0 – f/5,6, then your maximum aperture at 70mm will be f/4.0 but will shrink to f/5.6 at 300mm0 Whereas a 70-200 f/2.8 can maintain f/2.8 throughout the entire focal range but can also go to the minimum aperture of you camera (often f/22 or lower),
Now that you have these basics down, you should be able to tell that the faster (smaller f-stopnumber) the better able the lens isto shoot in darker conditions and when used at the lens’ maximum aperture, the more pronounced the bokeh effect will be