Today is a nice sunny day. I was just out with my camera trying to capture some birds. How did I select my exposure settings? In a previous post, I discussed the exposure triangle. Aperture, shutter speed and ISO make up a trio of settings that combine to create the proper exposure. There are a couple basic exposure rules that can get in the ball park of the proper exposure in certain situations.
As I mentioned, today is a nice sunny day. The first exposure rule is called Sunny 16. This is where the aperture is set to f/16 and the shutter speed and ISO are set to the same value. Back in the film days, ASA (now ISO) was a constant for the roll of film. If I had a roll of ASA 100 film, that is the same as saying ISO 100 for a digital camera. ISO is an international standard measurement for exposure.
On a sunny day, like today, I can get a proper exposure by simply placing my camera settings to f/16, 1/100, ISO 100. This may be good for landscapes and still objects. However, I was hand holding my 400mm lens while trying to capture a moving object. This means that I need to adjust my exposure settings to compensate for these variables.
The general rule of thumb for getting a sharp image while hand holding a lens is to use a shutter speed equivalent to the focal length of the lens. For my 400mm lens, this means that I need to use a shutter speed of 1/400 or faster to stop any motion induced by myself. Keep in mind that I am still shooting the same bright sunny scene.
I want to keep the same exposure reading I had when I was at f/16, 1/100, ISO 100 with a new shutter speed of 1/400 to compensate for hand holding a 400mm lens. My options are f/8, 1/400, ISO 100 or f/16, 1/400, ISO 400. There are actually more combinations of the exposure triangle that achieve the same equivalent exposure value. It is up to me to decide how to balance the equation.
Perhaps the clouds build. This reduces the scene’s luminance. There is also an overcast 8 rule that looks like f/8, 1/400, ISO 400. I used ISO 400 because 400 speed film was a more typical all purpose film speed. However, f/8, 1/100, ISO 100 gives the same reading on the light meter.
Digital cameras have taken away some of these really good basics. I say that, because a camera can do all the thinking for a person and achieve a good exposure. Back in the film days, it took a little extra thought process before the shutter button was released. Yet, all the same fundamentals still apply and can be used in digital photography.
I shoot almost exclusively on manual mode. Automatic modes have purposes. They can speed up the process of taking a photograph. I just rely more on the fundamentals to get me where I want to be. In a way, I am challenging photographers to think more before they take a photograph.
Ask: what is the lighting of the scene? On the next bright sunny day, set the camera to manual with f/16, 1/100, ISO 100 and see how well it exposes the scene. Said with slight sarcasm: maybe automatic mode will become a thing of the past! Photography is more fun when it is not so automatic. So, remember the sunny 16 and cloudy 8 rules. Give them a try!