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  • Writer's pictureMark Paterson

What is the correct exposure for an Image? - Part 2

Following my "Breaking News" last week, this weeks post is a return to normal photographic talk with a lesson in how to expose for an image in the real world. So this past week I visited a local beauty spot and decided to put into practice what I talked about in the previous post. As a recap, I was talking about how the shutter speed, aperture and ISO changes the amount of light that hits the sensor, which in turn, creates the image that is recorded.

As a general rule when capturing a scene that has some brightness (known as highlights), as well as some darkness (known as shadows), the photographer has the option to do 1 of 2 things. They can use filters to darken the bright areas so that it is equal exposure all around. Or, they can do the following.

Step 1 - Expose for the Highlights. This is where the sky in this instance fills the frame and adjusting the shutter speed until the reading is correct.

Correct exposure for the Highlights (Sky)

You will notice that the sky is looking very dramatic, which was what the reading the cameras built in light meter said was the correct exposure. BUT. You will also notice that the rest of the image looks very dark. The reason being is the exposure for those parts are NOT correct, which leads us onto step 2.

Step 2 - Expose for the Shadows. In this case filling the camera screen with the darkest part of the image, which was the shadows in the trees

Correct exposure for the shadow areas (trees)

In this image, the other parts of the scene looks to be correctly exposed, however, the sky is looking too bright. Now the dilemma of which shutter speed to choose to preserve details in both the shadows AND highlights.

And to do that, I need to use maths to get the ideal setting. By using the exposure for the sky (which was 1/1000th of a second) and the trees (which was 1/250th of a second) the ideal exposure for this shot was 1/500th of a second.

The image you see below is the correctly exposed image according to the cameras meter, and this result was only possible because of the choices I made earlier in the day when recording the scene.

Correctly exposed in camera image

The sky doesn't look TOO bright, and you can see the details in the trees (as well as some shadows) which then enabled me to be able to edit the image.

This image is a truer representation of what the scene was like at the time of shooting. It was only achievable because I had found a compromise between the exposure for the bright sky and the shadow areas. So by being able to make the settings required to meet half way, the starting image was able to produce the information needed to produce this result.

In the next post, I will be doing something slightly different. I mentioned that I had to do some maths to get the ideal exposure, so next will be informational on the different values that are used in photography. That is something called STOPS.

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