Exposure

"Proper exposure is the basis for any photograph, so when taking a photograph understand what exposure is. Most new photographers in the digital have no great understanding of exposure. It all relates back to the 18% gray card.

The 2 common examples are photographing a black cat on a white carpet or white eggs on black velvet. If you let the meter in the camera meter the scene then you will get a gray cat on a very dirty looking gray carpet or you will get grey coloured eggs on a dark gray velvet.

Here are a couple of websites to check out, the first one is very informative."

The Complete Guide To Lighting and Photographing Small Objects with your Digital Camera

The perfect exposure retains details in both the highlights and shadows. For the autoexposure system, this is as difficult as your parking a very large car in a very small garage. If there is even a little too much exposure, the image is too light and details are lost in the highlights. If there is too little exposure, the image is too dark and details are lost in the shadows.

When confronted with any subject lighter or darker than middle gray, you use exposure compensation to lighten or darken the photograph that the camera would otherwise produce. The amount you increase or decrease the exposure is specified in stops. For example, to increase the exposure 1 stop, you specify +1 to open the aperture or slow down the shutter speed. It's easy to use exposure compensation because you can preview your changes on the monitor and then immediately review the results.

To lighten a picture, you increase the exposure (+). This is useful for setups where the background is much lighter than the subject, or when photographing very light objects, such as white china on a white tablecloth.

To darken an image, you decrease the exposure (-). This is useful for setups where the background is much darker than the subject, or when photographing very dark objects, such as black china on a black tablecloth.

Understanding Exposure

The extremes of brightness that one encounters in the natural world are not that varied. For this reason there is the so-called Sunny 16 rule. This says that on the brightest day normally encountered the proper exposure is roughly the reciprocal of the film speed at f/16. Thus, if you are shooting ISO 200 film then the exposure will be 1/250 second @ f/16. This is the same whether you're in Auckland or Amsterdam, mid-summer or mid-winter.

From the extremes of a sunny day outdoors down to typical indoor room lighting covers a range of about 10 stops. With the exception of seldom encountered situations like fireworks, cityscapes and moonlight scenes these 10 stops encompass every lighting situation you are ever likely to encounter. Only on the ski slopes or at the beach will you need to stop down one more stop beyond Sunny 16 because of reflections off the snow and sand.

So, that being the case, why is exposure so difficult? Most people should have no problem in recognizing 10 different light levels, shouldn't they?

Understanding... Exposure Compensation

Exposure Compensation is a feature of a camera that allows you to adjust the exposure measured by its light meter. Usually, the range of adjustment goes from +2 to -2 EV in 1/3 steps.

This means that you can adjust the exposure measured by the light meter by telling the camera to allow more light in (positive exposure compensation) or to allow less light in (negative exposure compensation).