Digital 101 Exposure Part 1

In conjunction with the Nikon Talk Forum at DP Review

Exposure...

Talking about exposure is like climbing Mount Everest without  oxygen. It’s a subject that many photographers spend their whole lives learning. To try to discuss it in simple terms for the novice is a challenge. Once again the goal is to keep it simple and provide the basic building blocks on which you can learn.

Exposure is the amount of light that reaches the film.  This is controlled by the aperture and the shutter.

The aperture controls the intensity of the light that reaches the film and the shutter controls how long the light strikes the film.  Thus the relationship between the shutter and the aperture is clear and you can see that if one increases the other must compensate. If you think of this relationship like a scale where if everything is in balance the two sides of the scale will be level but if you add weight to one side and not the other it will be out of balance. This explains a lot of how metering systems work.

To understand exposure you first have to look at the way a camera's metering system works. It’s a principal called 18 % reflectance. The best way to look at this is if you take a range of color from solid black on one end to solid white on the other a metering system will try to read somewhere in the middle. Thus the term middle tone. So what ever you point your camera the metering system will try to find the middle ground on which to base its exposure.

The basic camera looks at the whole picture area and tries to set an exposure that will average every color in the viewfinder and make the best, averaged exposure. That’s why you have heard of the gray card. The gray card has a gray color that is considered to be middle tone or more importantly 18% reflectance. If in doubt meter off the gray card and set that exposure manually in your camera.

With a digital camera you have many advantages over film and exposure is one of them. There is an article in this months Popular Photography about using a digital camera for an exposure meter. With a film camera with the best exposure meter you still can’t see the exposure until processed. With digital that’s not true and we see what we get now. So with a digital you can shoot till you get it right.

The basic metering system will give you good images about 80% of the time. The other 20 % will be affected by backlighting, light against dark, dark against light, pictures around the water or snow or really Difficult images like a dark colored squirrel in the snow that has strong backlighting by the sun.

We will look a many different examples these next two weeks of exposures and how to achieve results. Yes I said two weeks. We cannot go thru this subject quickly as it is the foundation of every image you will ever take.  I will try to post a new subject on exposure every two days and leave time in between to discuss and show examples. As always have fun and if we learn a little in the process then great. Wednesday we will discuss the different features of the cameras metering system and how to use them.

Troutman

Click here to discuss this tutorial on the Nikon Talk Forum at DPReview...

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