Well I’ve had a seriously busy week. I’ve not stopped at work and have been so exhausted on an evening I’ve been falling asleep on the sofa. Hence no posts since last Foto Friday. Thing is I don’t want to start something like this and then immediately start missing them (if you’re a Pratchett fan, think Sam Vines and ‘Where’s my cow?’) so I hope you’ll forgive me if todays Foto Friday is a little shorter than the previous ones.
Ok then, so we’ve got our camera and a bit of an idea about how we get an image on the image sensor. Time to start exploring those modes that aren’t fully automatic. First up is ‘Aperture Priority’, usually shown as either ‘A’ or ‘Av’ on your camera. On mine there is a little dial which you turn round and it’s shown as Av.
This is a semi-manual mode where you make some of the decisions and the camera will work out the rest for you. In this case you control the size of the aperture or ‘hole’ which allows the light in when you click to take a photograph. Remember the wider the hole the more light will come through in the same amount of time. Think of the pupil in your eye… if it’s dark and you need more light to see then your iris makes your pupil bigger. Bright sunshine and the pupil is smaller. We humans don’t have to think about this but it’s worth spending some time to learn about it on your camera.
If you use Aperture Priority then you control the size of the hole and the camera will work out how fast it needs to open and close (speed) to get a well exposed photograph. So what would you use it for? Remember those beautiful shots where a flower, person, dog, wombat, whatever, is in perfect focus and the background is blurred allowing the subject to pop out and look amazing? You know where I’m going with this now don’t you……
Think of a line extending from your camera to the back of your photo (in my example the wall). The wider the aperture (hole) then the smaller the amount of the line that will be in focus. The size of the aperture is known as the ‘f-stop’ the smaller the number the wider the aperture (yeah I know that doesn’t seem logical but hey that’s life).
So lets look at the example above (shot in the exotic location of my front garden, oh the glamour of it all). On the left I focused on the flower and opened the aperture up as wide as my lens would go. This means f-stop 2.8 (remember a small number means a wide hole). The result is a shot where a small area in front and behind what I focused on (the rose) is in focus, the rest gets progressively more and more blurred. In the middle is f11. The area in front and behind the rose which is in focus is larger and has just about reached the wall of the cottage. So the wall now appears much more in focus. On the right is f22 (smallest hole) so the maximum is in focus. The wall is now even sharper. We can see it better if I blow them up a bit…
Now obviously the length of time the aperture is open was different for both shots, but we can let the camera worry about that.
So, now you know that what people are talking about when they mention f-stops. The amount of the image that is in focus is known as the ‘Depth of Field’ and I’ll look at more effects you can get my manipulating this next week. Take care, have fun with your camera, and let me know how you get on (yes that was a hint hehe)….
Mara
