Exposure Parameters : Part II- Aperture

Aperture is a very  important Exposure parameter.Normally you would have seen values like F2.8 ,3.5 ,....F8.0 and beyond, these values correspond to the aperture values.

Having said that , What is aperture and why is it important ?

If camera lens can be compared to eye, then controlling aperture plays the same role as how you contract / dilate your pupils depending on the light conditions and region of focus .Just remember this whenever you want to operate with aperture.

Now coming to why is it important , Aperture is a very important parameter to control the depth of field and  rule of thumb is Lower the value, Wider is the lens and thus smaller is the depth of field.And higher the value , Lens is narrower and the depth of field is higher and thus the range of shutter speed available also reduces.Refer to the picture below to get better understanding.

Now why do you want to control Aperture ? In case you are taking a landscape/nature picture normally the lighting will be pretty good and you can manage with low shutter speed and thus you can go to higher F stops to get better depth of field(You don't want the near by tree to look more prominent and mountain to be out focused right?). 

Why did i mention lighting ? I had mentioned earlier that smaller is the aperture wider is the lens as it is indeed the denominator , So when you want to include higher depth of field and thus increase the aperture value to say F8 , The lens is much much narrower and the amount of light that is incident on the lens is low, thus if you try a higher f stop in bad light conditions the picture will be under exposed and to compensate for that you either have to increase the ISO value or reduce the shutter speed so that the lens is well exposed.

Why do you want to take pictures with limited depth at all ?Is  comes quite handy when you want to take a close up snapshot of a flower/bunch of berries/fruits or just the face of a person/animal standing right infront of you and you dont care about the background, As in this scenario you will be taking at a lower Fstop say 2.8 this will allow a wider range of shutter speed and also allows you to operate at lower ISO. 

But in case you have taken a picutre at higher Fstop and you want to give higher priority to a small part of the screen than the entire setting , Go to picasa and try out the soft focus option(with different radius and amount ) that is available.

And  the best way to learn is to try out different options It is ok to take any number of pictures , as far as you know that you are getting better with each picture.