Or, as my wife asked me earlier this evening
Why are you taking photos of the clothes line in the rain?
I’d mentioned earlier in the week about being so unhappy with the results of my weekends snapping. One of the problems I had was that I was trying to learn a bit more about Aperture and when I reviewed my results I couldn’t see what went wrong.
Here, let me show you….
(1/160, f/8, metering – matrix, focal length – 47.0mm, 12/08/07 15:56)
(1/8, f/36, metering – matrix, focal length – 47.0mm, 12/08/07 15:56)
Now, apart from the image on the right (or above – damn you blog editor thingy!) being a little darker. Changing the aperture appeared to do squat.
But, the theory I’d been told/read/guessed was this -
Aperture is the size of the hole in the lens that light can get through.
The amount of light hitting the lens can be controlled in two ways
- By opening or closing the aperture
- By increasing or decreasing the length of time the shutter is open (shutter speed)
You achieve a level of brightness within the image by complementing aperture and shutter speed. A smaller hole will require more exposure time
Aperture is measured in stops, typically fractions of how much of the lens is open and is referred to as a F number. F/2, F/4….
- F/2 effectively means the lens is half open ie: 1/2
- F/32 effectively means the lens is open to 1/32
OK, so far? Yeah so was I.
Now, apparently a large hole (small number) like F/2 would mean that the depth of field would be reduced. Something to do with less exposure time and beams of light and Star Trek stuff I think….
So, why did my two images with vastly different apertures look basically the same?
I asked a friend in work today (thanks friend!), who didn’t point and laugh and didn’t just mutter under his breath (thanks again friend!), but explained my mistake. Put simply…
The focal point in the shots above is basically infinity (not beyond it Mr Lightyear, no siree) and getting a shallow depth of field on something that far away is always going to be a problem.
He suggested I try to “focus” on something instead.
So, I did.
And here’s the results. Ignore the pictures, or rather ignore the content of the pictures, its just an example.
(0.6s, f/32, metering – matrix, focal length – 55.0mm, 16/08/07 19:19)
(1/5, f/18, metering – matrix, focal length – 55.0mm, 16/08/07 19:19)
(1/50, f/5.6, metering – matrix, focal length – 55.0mm, 16/08/07 19:19)
So, hopefully what you can see here is that as the aperture changed (opened – the number got smaller and the hole got bigger!), the background became more blurry and the shutter speed increased.
So, what are the lessons learned tonight?
- Big holes have small numbers (Aperture is effectively 1 over the number)
- Increasing the hole size reduces the shutter speed
- Little numbers give shallow depth of field (blurry backgrounds)
- Standing in the rain taking photos of a clothes line may confuse your wife and make you look like a twonk
Lord, I hope that’s right.