In this beginners lesson series we are going to understand Aperture of the lens and its effect on photographs’ lighting and depth of field.
Dead Easy Definition
The aperture is referred to as the opening of the lens. In DSLR cameras we have full control over how much we want to open a lens. And how much we open the lens will decide how much light comes into the sensor of the camera.
How to read specifications.
The opening of the lens aperture is specified in terms of f number for example
f/2.8 , f/14 etc
Now Rule of thumb no 1: The smaller the f number , the larger it will open and more light is allowed in.
The bigger the f number , the smaller it will open and less light is allowed in.
Now in order to understand aperture without distraction we are going to work in aperture priority mode ie we will have a full manual control over aperture of the lens only and we will let the camera decide the shutter speed by itself to keep the subject illuminated well enough.
Now we generally say that the shallow depth of field is controlled by aperture so
Rule of thumb no 2: lower the f number or larger the opening, more shallow depth of field, ie blurred back and foregrounds.
higher the f number or smaller the opening, lesser depth of filed, ie more clearer backgrounds and foregrounds.
The depth of field or bokeh also depends upon distance of the subject, closer the subject more depth of field.
In this illustrative tutorial, i have used 2 prime lenses.
1. Tamron 90 mm Macro
2. Nikon 50 mm Prime
Image 1. ISO 100 90MM f/3.2 1/8 sec Tamron 90 mm Macro
Image 1 and image 2 are almost similar although image 2 is taken at f/1.8 and was expected to give more shallow depth of field, but image 1 at f/3.2 covered that up with closer subject distance ( its a 90 mm lens)
Image 2. ISO 100 50MM f/1.8 1/25 sec Nikon 50 mm
Image 3. ISO 100 50MM f/18 5.0 sec Nikon 50 mm
Image 4. ISO 100 50MM f/6.3 .8 sec Nikon 50 mm
Image 5. ISO 100 50MM f/1.8 1/20sec Nikon 50 mm
Comparing image 2 , 3 , 4 makes more sense as they are taken from the same lens and at same distance, the depth of field has changed dramatically.
In image 5 the distance is shortened thus more shallow depth of field.
Hope this helps
GO BACK TO INDEX OF LESSONS