Lesson 1 - three things that control the light and your pictures

Photography is all about light. Light striking the sensor (what used to be the film) and causing a chemical reaction (now electrical) and leaving a vision of what you have seen.

There are three main ways that we control that light and therefore affect the pictures. 

ISO - Iso simply means the chemical sensitivity of the film. Or in today's speak the electrical sensitivity of the sensor in your camera. If you are taking pictures in low light - the sensor needs to be more sensitive to collect more of the light...if you are shooting in bright sunshine - the sensor will be less sensitive.  The sensitivity is measure in ISO. The lower the ISO setting - the less sensitive the sensor is. Luckily - you don't need to remember or understand how this works...all you need to remember is that if you're shooting in bright sunshine - select a low ISO number (say 100- 200) and if you're shooting indoors without a flash, or in the evening light, or at night time, or on a cloudy day...make your ISO a little higher. In your camera the ISO range goes from 100 right up to 25,600...which is an excellent range. How I remember it is very easy....as the light goes down the ISO needs to go up...a bit like a see-saw.

The downside of using a high ISO is that the picture can tend to be a bit 'grainy'...but it probably isn't going to be enough to worry about. Here's a picture that I took at a high ISO...and you can see what I mean....

It's not really a problem unless you want to really blow the picture up - but if you do - you will clearly see the grain. Double click on the picture and you'll see what I mean :)

Shutter Speed - Shutter speed is very simple. It's the length of time that the shutter is open for allowing the camera to capture the light to make the photo. Imagine you're taking a picture of something that is moving......if your shutter speed is fast - this will freeze the action...a bird mid-flight, a person doing sports, water in a fountain, firework bursts in the sky, leaves being blown around in the wind etc etc...all of these would require a fast shutter speed. But if you want to be creative you can do many things with a slower shutter speed. Remember though...if you use a slower shutter speed and your camera moves at all...the resulting picture will be blurry. A tripod can be required for slower shutter speeds..or - put the camera on a hard surface...Also - if you're shooting in lower light you may find you need a longer shutter speed or the picture will just be very dark. Shutter speed is measured in fractions of a second...and again in high light conditions (bright sunshine) you need a faster shutter speed - or all you will see is a big page of white light!

Aperture - the final thing is aperture. Your lens opening (or aperture) is made up of blades. A bit like a cave entrance in a sci-fi movie! The aperture setting simply means how open or closed the hole is that lets the light in. So again, it helps to control how much light hits the sensor. In darker conditions you would need a wider aperture (more open) and in bright conditions you would need a narrower aperture (less open). The aperture also affects something call depth of field...more about that in the next post. For some reason known only to the boffins...aperture is measured is something called f-stops. And they're fractions. So if you see f32...that actually means f1/32......

So - that means in real terms that the higher the aperture number - the less light is coming into your camera. f4 is a much bigger hole than f32.  Each lens has a different aperture range - depending on which lens it is. Your 18-55mm lens has an aperture range of f3.5 - f5.6.   All you need to remember is the higher the number = less light.