Over and Under Exposure. ( Briefly)
Giving your film more exposure than necessary will result in overexposure. Pictures will be pale or light with poor washed out colours.
Giving your film less exposure than necessary will result in under exposure. Pictures will be dark with poor detail in shadow and dark areas.
You will have realised by know that there are three factors involved in controlling exposure.
They in turn share another common factor, which crops up a lot in photography, the 'stop'. Changing either of them by one full setting will always half or double the exposure the film receives.
Increasing one and decreasing the other by the same number of 'stops' gets you the same exposure.
Putting it all together.
Here is what will happen when you press the shutter release button:
- The mirror will flip up out of the way.( SLR) That is the clunk you hear.
- The aperture will 'stop down' to the selected value.
- The shutter will open then close.
- The mirror will come back down.
- The film is wound on by one frame and the shutter is reset. Automatically if the camera has a winder or manually, by you, if it doesn't.
You may be wondering why you can't just stick with one film speed, one aperture and just vary the shutter speed or one film speed, one shutter speed and vary the aperture. Well you can, in fact most cameras will allow you to do both of those things. What you need to know is how you do it and more importantly why you would want to do it.
Coming up next.
In the next couple of bits we will look at the unbelievably interesting use of shutter speeds and apertures. There will be a few pictures or illustrations so it should be a bit less of a drag than this bit was. Also, just to make sure you are paying attention I am going to set you a little test. Not too hard, just enough to make sure you know roughly what is going on with the stuff we have just done.