Ok, before we go any further, let me just point out, I am no genius when it comes to photography. I learn by doing things. So if you are like me and need to go and do things to learn, this little BLOG entry maybe of some help to you too.
This whole dSLR business was completely new to me about 10 months ago, then I bought a second hand Canon EOS 300D and I had a rather steep learning curve to try and come to grips with. f stops, apertures, exposure, shutter speeds etc etc etc. Having only used an old IXUS II before, point and shoot had been my world.
One thing that always intrigued me as a photographic ignorama (that may not be a word) was how those slick photos with something in focus and the rest out of focus was done. So I asked a few stupid questions, Googled like a demon and found out the answer was Aperture settings. Ah, so off I go. Change to manual mode on the dSLR and everything is stuffed up. As I go for greater depth of field, every thing got dark and blurry. As it turns out, exposure is a VERY important thing in photography. Well I’ll be buggered. More reading and it turns out that aperture and shutter speed have a relationship. One that I may venture into when I understand it better.
Ok, so set the camera to Aperture Priority and have another crack at it. Now you can see from the picture to my left, or your right, and you might have to click it and see the larger version to appreciate it, that I have focussed on the front of the formula 1 car (thats the red car at the front for the car racing ignorama). Notice the dark green car at the back is out of focus, or OOF if you are reading photographic forums. Ok, that was taken with an aperture setting of f/5.6.
f10
Originally uploaded by norbography. Ok, here we have one that was taken at f/10. Again you may need to click it to see it in its massive glory. You should be able to tell the differance pretty easily. Forget the stuff up in exposures, look at the sharpness on the next couple of cars back. They are slightly sharper.
Now, this one was taken at F20. Note the sharpness of all the cars now. That, in a very, very basic form is how aperture settings effect depth of field.
Obviously, there is alot more to it than just that. For a much more in depth look at it, and better pictures too I must say, see this terrific site.
I hope that helps. Thanks to daisydingletoy at Flickr for the prompt to pull my finger out.