ThinksMedia

Aperture and Depth of Field

Sunday, April 19, 2009

So there you are playing around with the aperture, figuring all the possabilities you can make happen when you notice that one of the key thiings that aperture does, especially when your pretty close to your subject is change the Depth of Field.   The wider your aperture, the less of the things in front of and behind your Focal Point are in focus.  At first you panic…what, my pictures are all going to have blur in them…but soon you realize that not only can the blur (aka Bokeh) not detract from your images, it can actually be used to make the subject of your photo pop, and suddenly, some of your snap-shots are staring to look like photographs.

In the above photos you will not I have taken the same shot with the aperture ranging from f-18 (very small, and the practical limit before defraction begins for my particular camera) and f-2.8 the widest open that this lens will go.   Notice that at 2.8 very little is in focus, and for this shot its probably a little too much blur, but at the other end of the settings, f-18 has everything pretty sharp and just is a little boring.  At the above sizes, f-8.0 seems to be about where I think the best look is, but thats only at these small sizes, at larger sizes, it becomes apparent that even at f-18, a picture taken this close still have pleanty of blur to keep it from getting boring.

So you see that its more than just how much blur or depth you want, you should also consider the use of the final image.  Acceptable blure for a small web piucture may end up looking way too fuzzy on a magazine cover.  Listen to the show for a more detailed explination of these concepts!

Some basics on Depth of Field:

1. The apparent sharpness of a wide angle lens is more than that of a standard or telephoto lens.

2. The smaller the aperture the more depth of field you get.

3. The farther away the object you focus on is, the more depth of field you get.

4. On average, you will have more in focus behind your focal point than in front of it.

5. All these rules can be combined, ie: shooting with a small aperture with a wide angle lens at an object that is a few hundred meters away will yield a very DEEP depth of field, while shooting with a telephoto lens at a wide aperture focusing on something very close will give you a very shallow depth of field (one reason macro photography is challenging is because you are shooting so close to your subject that its hard to get any depth, even at very small apertures)

Podcast: Play in new window | Download