At one of the recent meetings of our new Camera Club in my town, we spent an evening discussing the basics of photography – aperture, shutter speed, ISO and the like for the benefit of some beginning photographers. We were asked to take two images to illustrate focal depth resulting from different f.stops. These were mine – some tiny fungi that had grown on firewood in the woodshed. Taken using a 100mm macro lens, and the clever in-camera natural looking HDR mode of the 5D MkIII giving perfect exposure for the whole image in natural light.
A very sharp image from front to back – f/20
An image with very shallow depth of field – f/2.8
For those who might need a little visual reminder, this diagram shows the relationships discussed above.
Diagram found on Google, copyright of http://www.momentologyphotography.com/