3 - The 3 main variables

As photographers, we must become fluent on reading the ambient light, change it, or complement it with reflectors, flash, etc...

You and your camera will eventually become one organism. In the process, you will need to understand how the camera “sees” light. As little as you may like theory, and I will assume that if you are visually attracted to images like all of us who love photography, that side of your brain is more developed than the other one. But still, we need to understand the techniques well enough in order to generate consistent and predictable results every time. Like anything else, we are only entitled to break the rules when we know them down cold. Taking hundredss of images that you never go back to look at, is an absolute waist IMO.

Look at these 3 images below, and the 3 set of numbers on the top of each. We will come back to them, and we may have to come back to them many times.

The matrix below shows the 3 variables that we photographers must master. The relationship between these 3 variables determine the correct exposure and the intended look or effect in an image.

1. Aperture,

Let’s start talking about the effect that the lens aperture can have in your image.
Those three images at the top, have very different aperture from each other. Look at the aperture value on the right (e.g.: f/22) and look at its effect on the image. The camera was set on a tripod for all 3 images, and focused on the first chess piece. So the piece on the front, our main subject, is always on focus and sharp, the one on the back is only sharp enough on the first image at the top, with the aperture @ f/22. Because the camera was set on automatic mode, with AV priority (aperture priority) the shutter speed (how long the diaphragm remains open) is determined by the camera to have an average good exposure. More on that later.

The other extreme is the image on the bottom of the 3, which has a short depth of field. what is sharp is within a narrow plan, everything else, foreground and background is out of focus, or blur. Note then that as we open the diaphragm in the camera (let more light come in by a larger diameter), the shallower the depth of field becomes. That is the same way that our eyes work...as we focus our eyes on one thing, everything else is kind of blurred. This technique is much used to emphasize a subject within the image frame. Start paying attention how much this is used on movies, when two people are carrying a conversation. The one speaking is sharp, the one listening is blur, or out of focus. By the way, many people believe that there is something special and different about movies, but “moving pictures” are nothing more than moving pictures. That is why you need a director of photography to oversee the whole movie production.

Back to aperture …

A large aperture is also useful, or necessary in low lighting situations. The wider the aperture, the more light is allowed in to “burn the film’s light sensitive surface”, or digital sensor. Low light, and a small aperture requires the shutter to stay open longer, so to allow enough light in the camera. Again, the relationship between these three variables should become second nature to us photographers.

Camera manufacturers keep on developing lenses and cameras that can capture better definition in their images with dim light. For more on our eyes and the camera diaphragm go here.

to be continued...