(skip these pages if you know)I've had an email requesting my 'How to' on NOT using the Auto setting on cameras all the time. In order to answer that, one must understand 'exposure'...
So, f2.8 for 1/500th of a second is ‘the same’ as f5.6 for 1/125 of a second. Before this information makes you think, ‘this isn’t for me’, it needs to be said, you can simply accept this is the case and move on.
These f numbers are not really understood by experienced photographers, other than, low ones come with big holes and let you have the person in focus and the background out of focus, larger f’s do the reverse. f16 will get the foreground and background in focus at the same time.
Getting the correct
exposure is achieved
by the relationship
of ‘f’ number and
High shutter speeds
require a larger
aperture or lower ‘f’
number to let in
more light. Used to
(larger ‘f’ number
f16 for example)
giving larger depth
of focus, are
longer shutter speeds
Large apertures such
as f2.8 lead to
small depth of focus
A lot of cameras have a dial that has PASM on it.
- Program is used to get the camera to decide what it thinks is a good combination between the 'f' stop and the shutter speed.
- Aperture Priority is used when you know better and wish to choose how deep your focus is. Shallow artistic depth of focus requires low numbers f2.8 for example. The camera sets the corresponding shutter speed to achieve the correct exposure.
- Shutter Priority is when you know better and wish to cause blur by using a long exposure time to, for instance, blur a waterfall. Equally you may wish to freeze a sports car by using a fast shutter speed, like a thousandth of a second. The camera will open the lens hole more if you use a fast time to let more light in, and of course, lessen the depth of focus.
- M is for Manual. This is when you take total control. Your choice of depth of focus and your choice of shutter speed. To get the exposure right you will need a bit more knowledge or a bit of... luck!
...start using your camera on something other than 'AUTO'