Another blog for Frogpondsrock 's Sunday Selections! Go and check out hers and all the others linked there!
As an enthusiastic photographer I am trying to come to terms with some of the basics of photography, and specifically the three things that effect exposure: aperture of the lens, shutter speed and ISO setting (film or more commonly these days the sensor). I've loved longer exposure times for some time, particularly the effect of a long exposure on water in a creek, stream or waterfall. Will save that for another post I think.
More recently I've been thinking more about aperture, and in particular how this effects the depth of field (DOF) of my photos. In many ways I was forced into this position by purchasing a macro lens, which is quite brutal if you dont get your head around aperture settings! All but one of these photos were taken with this lens, a 100mm Canon f2.8 L Macro IS USM.
In the age of the digital camera most DSLR's and many high end compacts have settings to allow manual control of aperture, shutter speed and ISO of the sensor. I don't pretend aperture and DOF is easy, but I will pretend it is for the sake of me being able to write about it!
Aperture is measured in f stop numbers. The aperture is a mechanism in the lens that closes to varying degrees during exposure to vary light hitting the sensor/film. The smaller the f number, the larger the opening of the aperture, and the smaller the depth of field. Simple.
The photos below all have a small f number, thereby a small depth of field. The depth of the area in focus not only depends on aperture, but also the focal length of the lens (eg 50mm vs 100mm) and the distance between the lens and the subject. See, still simple.
To demonstrate, heres a photo of a butterfly. The aperture is f2.8, the smallest possible for the lens. The distance between the lens and butterfly was about the minimum distance possible, producing the greatest magnification, with the smallest DOF.
here are a few more shots, all with minimum possible aperture
Increasing the aperture a little now, giving a slightly larger depth of field, but still throwing the background out of focus - f3.5
And now to slightly larger apertures..
f7.1
f7.1
f9.0
