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Exposure : Aperture : Shutter Speed : ISO : Composition : White Balance : Flash : Mega pixels


EXPOSURE


On a DSLR (Digital Single Lens Reflector)
...........or SLR (film - Single Lens Reflector)


There are 3 things that effect your exposure / the amount of light reaching the sensor:

Aperture.......................Shutter Speed.......................ISO / Film Speed



Aperture:
This sets the size of the hole through which light enters the camera

Shutter Speeds


These numbers are known as ‘F stops’, you refer to them as F16, F8 etc

Shutter Speed:

1000 – 500 – 250 – 125 – 60 – 30 – 15 – 8 – 4 – 2 – 1” – 2”


These are fractions of a second i.e. ¼ and ½ of a second are represented by 4 and 2, the whole second appear as 1”

Each ‘stop’ on the
aperture or shutter speed exactly doubles or halves the amount of light reaching the sensor / film i.e. if you change the shutter speed from 4 to 2 (quarter of a second to half a second, the hole is open for twice the amount of time so double the amount of light gets through to the sensor).

“Aperture and shutter speed work together, you cannot adjust one without adjusting the other”.



Image Exposure Example
When you look through your view finder you will see a set of numbers, this is the exposure meter, (usually displayed at the bottom)
-2...-1...0...+1...+2
This indicates your exposure, it goes from 2 stops under exposed (-2) to two stops over exposed (+2), to correctly expose your image you need to be at ‘0’, look through your camera, with the mode set to manual, and play with the aperture and shutter speed settings to see how this effects the exposure meter.




ISO or Film speed:
There are a wide range of ISO settings, these tell us how sensitive the sensor or film is to light.

ISO 6400 – 3200 – 1600 – 800 – 400 – 200 – 100 – 50


Note how the numbers double, like the shutter speed and aperture each setting is twice or half as sensitive as the next



Balancing Light.
When you have discovered a correct light reading, you can then make some choices, you can change the Aperture, as long as you change the Shutter Speed to compensate. See the example below.

“This gives you a range of options for your shot”

Image Exposre Grid Example
Click to Expand

To much light = over exposed pictures that appear to light
To little light = underexposed pictures that appear to dark


Which means
Overexposed = reduce light by closing down the Aperture or increasing Shutter Speed
Underexposed = increase light by opening up the Aperture or decreasing Shutter Speed





Remember exposure is an artist choice, here I have exposed for the bright areas, dropping much of the images into darkness... Rather effective!

silhouettes photography example




If you are new to DSLRs then set the ISO to 200, leave the flash alone and spend a few days in good daylight experimenting with the Aperture and Shutter speed Settings; start with reading the Aperture page.

For the more experienced of you who already have a good grasp of the meaning and effects of apertures / shutter speeds / ISO settings etc, then have a look at our tips page, for some more advanced topics.


© Nigel Watts 2011-2016 Contact/About