Through the Lens: Impalas under the Ebonies

13th July 2016

In an earlier post, I mentioned that this impalas image was my favourite from a safari in Nsefu last week. I love the arrangement of the antelopes, and the light falling across them. But there was also an element of satisfaction when the shot worked, as the bright contrasting light meant it was a tricky exposure. Let me explain by taking a look at the original shot:

Here's the original shot, straight out of the camera.


The original image shows that there is a large range of 'tones' - the brightness of certain areas of the image - across the scene. The impalas are brightly lit, whereas there are dark areas of shadow under the trees. This gives a challenge to the camera's light meter and exposure calculations since there is a wider range of tones (black through to white) than the camera can capture.

Since cameras see brightness in black and white, let's convert the original image to black and white so that we can see what the camera saw.

And here's the original shot, converted to black and white with no other editing.


When the camera looks at this scene, it measures the brightness throughout the frame (we assume here that we are using Evaluative/Matrix metering), and exposes to ensure that the average point is exactly half-way between black and white - we call this point middle-grey.

So I have added a bar down the side of the following image which is exactly middle grey - by comparing areas of the image against this benchmark, we can assess how the camera will behave.

On the left side, there is a bar filled with middle-grey. I have then 'painted' onto the image in red all the areas which are significantly brighter than this middle grey. I have also painted in blue areas which are significantly darker than middle grey.


As you can easily see in my crude graphic, the area of the frame which is darker than middle grey is much larger than the area which is brighter. This means that when the camera gives us our image, the darker areas will dominate the brighter areas which will lead to an over-exposed scene.

We can combat this by under-exposing our image intentionally (as I did here) so that the shadow areas stay dark and the impalas are not too bright - after all, they are our subject and we want to ensure that they are correctly exposed!

The final image is presented here. I used an underexposure setting of -1 to ensure that the relatively small impalas were not too bright.


It's perhaps counter-intuitive to think that an image with lots of dark areas will come out too bright. But when we keep in mind that the camera will always try to set the image's brightness to middle grey, it becomes clear.

If you would like to try this for yourself, take a photo of a piece of black paper (ensure that the image includes only the black paper). It will come out much lighter than true black. If you reverse the situation with white paper, you will see that it comes out much darker than true white!

Please ask any questions you would like to in the comments section below - I'll get back to you straight away.

Comments

Photo comment By Steve: Hi Ed, This is very well done and clearly explained. See you in 50 odd sleep nights!! Regards Steve
Photo comment By Edward Selfe: Thanks Steve. Glad you followed it and it makes sense to you. I am also counting down the days until our safari starts! Looking forward to seeing you and meeting your family. Best wishes - Ed

Leave a comment

Your Name
Your Email
(Optional)
Your Comment
No info required here, please press the button below.