How do we see? Admittedly some are better than others (without my glasses I’m as blind as a bat!). But, in order to see our eyes need light. It enters through the pupil, is focussed by the lens (or the other way around with glasses!) then hits the optic nerve where it goes off to be processed by the brain.
Camera’s work on exactly the same principle. It needs light (sometimes not very much) to be able to see the area in front of it to record the image. It is focussed by the glass in the lens, then goes through a hole in the lens (like the pupil), before passing into the camera sensor (optic nerve if you like) to record the scene. There’s a little more to it but that’s the basic.
Grab too much light in the recording and the image will be OVER EXPOSED. Don’t get enough light and the image will be UNDER EXPOSED. Mostly these are bad as you’re looking for a sweet spot somewhere along the line between the two that give a good balance of a few things (bear with me), but sometimes over or under exposing an image is what we want. The important thing is we need to manage and control the exposure and make sure it’s not down to guess work. On auto mode the camera does a lot of work for you and tries its best with the information it reads from the scene to take the most appropriately exposed picture – or so it thinks.
But, three things can be adjusted to control exposure – aperture, shutter speed and ISO. Getting all this right for the type of image you are trying to achieve is what we’re all about over the next few posts. Get them right in connection with each other and you’ll instantly make a massive jump forwards in the quality of your images from ‘point and shoot’ to something more refined, balanced and looking much more professional.
Let’s start with APERTURE.
This refers to a hole or a gap in the camera’s lens – the word simply means ‘opening, hole or gap’. It is closed by default and how wide it opens can be controlled in manual mode to determine how much light enters the lens and the camera sensor is exposed to. Open the hole really wide and a lot of light comes in, open it only a little bit and not so much. Change the aperture setting and you control the size of the hole.
The size of the hole is referred to as the ‘f stop’ and if you’ve seen ‘f2’ or ‘f13’ or similar then this is what it is referring to. There will be more on f-stops and how they relate to lenses in a later section.
What I find really confusing is that smaller f-numbers give a bigger hole. See the following image:
F2.8 gives a massive (relative) hole to let in lots of light, often used in low light situations, and f11is a much smaller hole that lets in hardly any light at all – much less than f1.4 and there is a sliding scale in between.
This is just an introduction to the concepts of aperture and I’ll write more on it in a separate post. This simple understanding should suffice for now. Hopefully.
