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  • Writer's pictureMark Paterson

What is the Correct exposure for an image?- Part 1

Before I start with this weeks post, just a little reminder of what I talked about last week and how this leads into this post. I mentioned that the SHUTTER SPEED, APERTURE and ISO all effect the settings that are required to be able to capture a good shot. One tool that a photographer uses is the in camera light meter to identify when the settings are “in the zone”.

Shutter Speed - The length of time that shutter is open.

Aperture - The size of the tunnel the light goes through

Iso - The sensitivity of the film/sensor

And it is a combination of these 3 factors that decide the image is recorded. So lets take a look at how these have an effect of the settings used.

On every camera, there is a part of the display that records the information of the amount of light that the camera sees. That is referred to the in-camera light meter.

The cameras’ light meter highlighted in the box

All camera makers have a system that allows the camera to identify whether the scene is too bright, too dark or ideal. As I use a NIKON camera, that will be the system that I use and if you have a Canon, Sony or any other make, the same principles still apply.

Essentially, to be able to take a well exposed image the line below the section needs to be in the middle, like above. The image I want to take would have the following settings;

Shutter Speed: 1/50th of a second

Aperture: F9

ISO: 800

Now watch what happens when the Shutter speed is changed;

VIDEO: Shutter Speed being adjusted on the camera

You would notice that the shorter time the shutter was opened, the bar moved to the right. This is the DARKER side and lets the photographer know that the image will turn out very dark. Especially in the case of 1/500th of a second. And would be too BRIGHT in the case of 1/2 of a second.

Now look what happens when the APERTURE is adjusted;

VIDEO: Aperture being adjusted with the same result

As you saw, if the Aperture was F32, that means a very small hole would let in the light, making the image VERY dark, or in other words an UNDER-exposed image. And with F5 too much light would be let in, giving an OVER-exposed image.

Which brings us to the conclusion of “What is the Correct exposure for an image?” and it’s something that a photographer is asked all the time. It varies from scene to scene, but by using the combination of SHUTTER SPEED and APERTURE you can get a balanced exposure so that the image looks great.

For this demonstration, I photographed a wall, something where it was evenly lit and not prone to changing conditions. NEXT WEEK, I’ll be out in the field showing how to use the cameras light meter to capture a real life scene.

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