Note: Completing this lesson requires a camera capable of manually setting exposure.
What is the right exposure? Not to make this complicated, but exposure is a choice you have to make. The exposure you choose determines how the image looks. But, we'll start with a basic understanding and work up from there.
Exposure consists of five factors:
- how much light is in front of you - which can be changed by adding lights or flash,
- how sensitive the film is to light - called ISO (remember, I use the word "film" to refer to whatever medium used for capturing the image, whether it is the Digital Camera's sensor or actually film,)
- the amount of light going through a lens - called the aperture,
- how long the film is exposed - called the shutter speed.
- what you want the image to look like, especially when light is beside or behind the subject.
If you haven't checked it out, there is a little more about how this works on the Camera Basics Page.
For the moment, we'll set an average exposure on an average scene.
If you’re camera does not have a built in meter - its really old. But, that’s okay. You’ll just have to buy a hand held meter. If you have an SLR or advanced point and shoot digital camera, spend some time with the manual to find out how to bring up the “Histogram” which graphically shows the amount of light in an exposure.
Exercise - set your ISO to 100, set your camera to ƒ16 and the shutter to 1/125th of a second. (Some digital cameras are limited to ISO 200 - which means you have to cut your exposure by one stop, i.e. use 1/250th instead of 1/125th of a second) With this setting, take your camera out during a sunny day, put the sun behind you and shoot anything - you'll have a well exposed image. This is called the "Sunny 16" rule.
To make life interesting, and your photography more creative, you can change the setting and still have the same exposure. These are equivalent exposures: Try going to ƒ11 at 1/250th of a second. Push it a little further at ƒ8 at 1/500th of a second. These are all the same exposure because the same total amount of light is hitting the film.
Of course, you're not always going to shoot with the sun behind you on a sunny day. For other situations you need to be able to find out your exposure with a meter. This can be in your camera or hand held.
Looking at any scene, your meter will give you a suggestion as to what exposure to use. Most of the time this is fairly accurate.
Using your meter, take a reading off of something with mixed tones in shade on a sunny day - you'll find the exposure is two or three stops slower than the "Sunny 16."
A final note - A meter is very handy for getting your exposure, but it does have a limitation. As said earlier, the meter thinks the world is 18 per cent grey. Most of the world is kind of like 18 per cent grey, but not all of it.
Look at what you're shooting. If its black (or very dark), your meter will try to make it grey - and make the exposure too light. Conversely, if you're subject is white, the meter will try to make it darker - or 18 per cent grey.
There are two more lessons on high key and low key photos which will help you handle more extreme situations.
Note: Be aware that some digital cameras have exposure compensation built in to prevent overexposure. If exposure is too bright the highlights could be "blown out" and detail lost in the brightest parts of the image. By artificially "darkening" the image, the camera makers try to make sure the exposures aren't too bright. This doesn't affect all cameras but it does seem to be the case for some. That means that the exposure needed in lessons 2, 3 and 4 may be slightly higher than suggested in the lessons. You might use the "expose to the right" method.