Aperture Priority Mode

Aperture priority mode on your dslr is probably the most useful of all the automatic/semi automatic modes available to you. It comes into its own in general use photography for ease of use and also for night and low light photography.

In aperture priority you decide the aperture ( F number) to select and the camera then calculates what shutter speed to use to give a correct exposure. This process makes aperture priority really useful in a variety of situations

To begin with, the fact you can set the lens aperture, ensures you have full control over the depth of field. If you want the whole scene from front to back to be well recorded (sharp) then you can set a high f number of say f8 or above (f12, f22 etc).

However, if you want, you can make the depth of field smaller by setting a lower f number which actually equals a larger aperture of say f4 or less (f2.8, f1.8 etc). This will ensure what you are focused on is sharp and then the rest of the image will fall away and blur / bokeh the further it is from your subject.

I setup a very simple shot to illustrate the difference in depth of field. (Balanced on tabletop, Aperture priority mode, D300, JPEG, Tamron 17-50mm VC, natural light).

Here is a shot at f16 – notice how my TV in the background is very visible, relatively well recorded

f8 – the background elements of the scene are still recorded, slightly less so than f16

f5.6 – less of the scene is recorded, and we begin to notice prominence of the oranges

f2.8 – the background blurs out nicely (bokeh) and brings more attention on the subject (oranges).