Exposure Triangle

Its been a funny day here weather wise, raining and grey in the morning and now it is blistering sun! Anyway, because of the strange weather I haven't really taken many picutres today. But I have been doing some more reading & practising with the settings on my camera.

Today as I was playing around with the modes that I was reading about yesterday I kept on coming up with a message saying 'subject is too dark'. This was whilst I was on the S (shutter) mode. I couldn't work out what on earth was happening with this so I posted a message on the DPS forum and I had lots of help from much more experienced photographers. Basically they were suggesting that I would need a slightly slower shutter speed than the one I was selecting (absolutley no idea which one it was now!) because the faster it is the less light it lets in - of course it all makes perfect sense now! They also suggested that read up on what they called the 'exposure triangle', which is what I've been doing this afternoon.

ISO, Shutter Speed & Aperture Size are the 3 elements that you can play around with as a photographer and each changes the way that light enters the camera & interacts when taken a photo.

ISO

Now, as a complete beginner as far as SLR photography is concerned I had absolutely no idea what ISO meant. I did vaguely recognise the term but couldn't work out why, but when I was reading I realised that I had seen it written on the camera films that I used to put in my automatic film cameras. On these films it was an indication of how sensitive the film was to light - the lower the number the lower the sensitivity & the finer the grain in shots.

With digital photography ISO measures the sensitivity of the image sensor, the lower the number the less sensitve the camera is to light. Higher ISO settings can be used in darker situations to get a faster shutter speed.

If subject is well lit & stationary and picture should not have grain then a low ISO should be used. But may want higher ISO for concerts, churches, birthday parties etc where a flash would not do the picture justice.


Aperture

Aperture is the size of the opening in the lens when a picture is taken. The larger the aperture the more light is let through. On the camera the aperture is measured in f-stops, the lower the number the larger the aperture.

If you use a large aperture this will DEcrease the depth of field in your picture & a smaller aperture will INcrease the depth of field. So, if you want a large depth of field you need to use a larger numbered aperture setting & smaller numbered for a smaller depth of field. When taking a picture with a small depth of field the background of the picture will appear more blurred so that the main subject of your picture stands out in focus. A large depth of field focusses on more of your picture.

Shutter

Shutter speed is the amount of time the shutter stays open whilst taking the picture. With digital photography it's the length of time that you 'image sensor sees the scene.

In most cases you'll be using shutter speed of 1/60th of a second or faster otherwise it may result in camera shake being evident in pictures. When using slower than 1/6th of a second a tripod will be needed.

When deciding on shutter speed you need to work out how you want movement to be shown, do you want to freeze the motion or blur it? To freeze it you need a faster shutter speed and to freeze it a slower one.

I'm looking forward to having a play around with these things over the next few days.