So what do all the different exposure numbers mean? Well, shutter speed, the pretty obvious. They're measures of seconds and fractions of seconds. The numbers relating to lens aperture, however, are a bit more confusing. But honestly, they do make sense. They equate to the area of the hole in the lens, the aperture through which light passes Now. In the old days, each number related to a whole one stop change on the scales looked a bit like this. In the simplest terms, each number is a doubling or harding of the exposure. For example, if I change lens aperture from F A 12 11 I'm having the quantity of light entering through the lens. If I do the opposite and change from F eight, where 5. I'm doubling the quantity of light similarly with shutter speed, if I change the shutter speed from 1 to 50th to 1 500 I'm having the length of time the shutter is open. If I go the other way and change from 1 to 50 with the 11 25th I'm doubling the time now to confuse things. Modern cameras enable adj...
ustments be made in smaller increments. 1/2 or 1/3 stops, and the scales now look more like this and notice the addition of the intermittent markers. But whatever the incremental change, the principle is the same. Each change increases or reduces exposure by a fixed amount. So now you understand the principle. Let's look at how this works. In practice, I'm starting with a portrait shot of the horse and rider. I've said the lens after a 5.6 and a shutter speed of 1 2/50 and this gives me a correctly exposed image. Next, I want an action shot. But my shutter speed 1 2/50 is too slow to freeze the movement of the horses, so I need to increase it. I'm going to put it upto 1 1/1000 which means the shutter is open for 1/4 of the time compared to my original setting of 1 to 50. To compensate, I need to open the apogee of in my original setting of 5.6 F four F 2.8, which quadruples the quantity of light passing through the lens. So now, even though my shutter speed and aperture have changed, the exposure value is the same which will give me the same correct exposure. Finally, I want an image that captures a sense of where we are now. I need a smaller aperture to get some detail in the background. I'm going to adjust my aperture from F 2.88 which is a three stop change. Again, I need to compensate for the loss of light by reducing the shutter speed by three stops that takes it from 1 1/1000 toe 11 25th. As before, my exposure settings have changed, with the total amount of light affecting. The sensor is exactly the same, resulting in the correct exposure. And you can see this if we compare all three images and look at the sky. The brightness is the same across each photograph. When it comes to exposure, you are constantly changing you the lens aperture or shutter speed. The question is, does it matter which of the two you change? The answer is yes, it does. In fact, it's about the only thing that matters