Photo 101: Exposure
Thursday, February 12th, 2009
by Joe
Exposure is a term that has a couple different meanings but the one we are going to be looking at is in the context of shutter cycles. All cameras have some sort of shutter, something that flips open the sensor/film and then shuts. That process is what “exposes” the sensor/film. Exposure is also the amount of time that you’ve left your sensor to capture the image. Ever get a picture that’s too dark? We would say that the photo is under exposed. Ever get a picture back that’s too light? Over exposed.
Almost all cameras come with built in light meters. Back in the day photographers would have to carry a light sensor separate from that of the camera. That sensor was called a “light meter” because it measured the amount of light and would recommend certain settings for the camera. Here are some photos of some light meters if you’re interested.
Ok, so all modern digital single-lens reflex cameras (or DSLR’s for short) all have built in light meters but what about Point and Shoot cameras (POS; no hidden meaning intended)? Well, yes, your POS camera does indeed have a light meter. That is how the camera can correctly adjust itself to get the best photo, however, most times you are not able to see it.
How to control your exposure? You can control your exposure with a combination of ISO, aperture, and shutter speed.
I took these images on medium format film camera called a Holga. It’s a cheap toy film camera and it’s pretty easy to mess up a photo. The pictures below were taken at a church in Costa Rica.
Notice how one image on the left is too light and can barely make out the church, where as the other one is perfectly exposed?
The reason one photo is more exposed than the other is because I left the shutter open for too long. Changing the shutter speed is a way to change the exposure or the amount of light that hits your sensor/film. Which brings us to next weeks topic, shutter speed.
