Whenever you ask anyone to explain "rule of thumb", you may get a different answer. From the dawn of time, fundamental facts and principles borrowed on familiar objects and symbols to explain things.

A priest, electrician or bridge builder would all have an explanation for using the thumb, forefinger and index finger extended at right angles. That symbol explains a lot of principles for me. As shown below, it is a very good way to hold a heavy camera perfectly steady. For an electrically minded person it is the relationship between volts, amps and ohms. Knowing one value determines how the other two values relate to each other.

So it is with photography. Aperture, shutter speed and sensitivity relate to correct exposure. Before the digital era, the sensitivity had to be manufactured into the film and it was called ASA. The Holly Grail of ASA was that the standard was set on June 22 at 11am at the South East corner of the Lincoln Memorial in Washington, DC. At that sacred place a camera facing West could take a perfect picture of a person when the shutter speed was f11 and the ASA and shutter speed were set to the same value. ASA sensitivity of 100 required a shutter speed of 1/100.

, trees and bright objects were influenced by flash, natural light and artificial electric light. That also was corrected by the digital revolution when cameras and image processing software could  add or subtract any color that was a problem. Click below for more.




Focus has been an issue from the beginning. There is more to focus than meets the eye. In some images, everything seems to be sharp, in others, only one part of the image appears clear and sharp. How do you control this?

To understand this...