Back To Basics - Exposure Demostrated
After talking so much about exposure and the controls you can use to, em.. well... control it, I thought I'd bring up some info that can help bring all the control info together.
As a solid base for demonstration, I chose to display and discuss a bit about a rule know as the "Sunny Day 16" rule. I guess that this rule is known to film photographers, and is of little use nowadays when all the cameras have built in light meters. But we can explore this rule and learn something about exposure from it.
The rule is simple: on a sunny day, set your aperture to f/16 and set your shutter speed to be as close to the ISO setting as possible. (There! All the three exposure controls in one coherent sentence. Pat on the back!). This is where this rule got its name - Sunny day 16. Image by Stefan Mendelsohn.
How to use sunny day 16 to set exposure? The basic use is already explained. Say you are taking pictures on a sunny day. Manually set your aperture to f/16. Now set your ISO to 100 and your shutter speed to 1/125 (remember - the closest possible shutter speed...). This is a great base to start moving to different exposure combinations. You can, for example, stop up your aperture in one stop to f/11 and increase your shutter speed to 1/250; Or if you want to freeze some action you need to stop up your aperture in three stops to f/5.6 and increase your shutter speed to 1/1000 - It all depends on your needs for specific apertures or shutter speeds.
Take shutter speed rule into account - Once you have the base aperture/shutter speed combination as a baseline, you should take the shutter speed rule of thumb into consideration. That means that the rule about focal length and shutter speed relations still applies. (And here is a little reminder: This rule states tat your shutter speed should be faster then your focal length)
If you shoot with a 100mm lens on a Nikon D70 (with a 1.5 crop factor), you should make sure that your shutter speed exceeds 1/150. Other wise you will have a blurry image. In the example above, it means that you should open at least one stop to f/11 at 1/250.
This rule can be used to determine exposure on not so sunny days - luckily this also works in other situations, only the name sunny day 16 no longer applies. You can see the other rules names that I made up to set the apertures on different weather conditions.
- Slight Overcast day 11
- Overcast 8
- Heavy overcast 5.6
- Sunset 4
Actually, these are not really inspiring names, just the aperture value you should use to be able to set ISO=Shutter speed.
A little self assignment: Next time you are out shooting on a sunny day, give the light meter a few minutes off. Set your camera to manual and take a few pictures using the sunny day 16 rule. When you are home, and comfortable, compare your estimations with those of the internal light meter, which one gave a better exposure?