Thursday, February 21, 2008

Technique (Exposure)- The Sunny f16 Rule

You woke up, got out of bed, and wiped a comb across your head. Then danced outside into the sun and took out your camera and had some fun. Took a look at your image and what a site! Something that looked, well, totally white? Oh, my gosh, what a fright! I wish I could, I wish I might, be able to take a better photo tonight.
I've had these thoughts a lot when I first began photography. However, they did not come out in a rhyme. More like zxbhg! Who in the heck ever set up f stops so a higher number meant a smaller opening ought to be shot! With a camera, of course.
However, after reading a great deal of photography material and learning a few tricks, I actually began to get images that were, well, pretty good. At least they did not look totally black or white. I've mentioned one or two of these "tricks" previously, like using your hand to figure how to get a proper exposure. Another trick of the trade is the "Sunny f16 Rule." I'll call it Rule 16 for short.
Rule 16 basically states that if your subject is in bright sunlight its proper exposure is 1/your film speed (ISO or ASA) at f16. Thus, if your subject is in bright light and your digital camera's ISO is set at 200, your exposure is 1/200 second at f16. Your camera does not have 1/200 second? Choose the closest shutter speed, in this case 1/250 second. This exposure will be very close. There are a couple of caveats (isn't there always at least one caveat with rules). The first- the subject has to be about a square foot in size or larger. It doesn't work with closeups. The second- this general rule is for a subject that is neutral in color (close to 18% gray). Well, all of the world is not 18% gray (Praise the Lord!). What do you do? Well, what did you learn to do earlier when a subject is either lighter or darker than neutral? You open up or stop down, respectively, to give the subject proper exposure.

One other thing needs to be taken into account. Very white subjects, say a white bird, will tend to wash out. For example, you will not see feather detail because the bird will be too white. In this case, it is a good idea to stop down about 1/2 a stop to keep that detail in the bird.

Now you can use additional information you learned earlier to decide what equivalent exposure you wish to use for your subject. Need a faster shutter speed to stop the subject? Well, you can use f11 at 1/500 second, f8 at 1/1000 second, etc. Need more depth of field? Use f22 at 1/125 second, f32 at 1/60 second, etc. We'll learn later why it is not always good to use too small and aperature (to high an f stop number).

1 comment:

peenkfrik said...

I guess my P&S does not have an f16 option.