Histogram & Exposure Basics

My cat Shiva photographed against her favorite white sheet. On automatic exposure mode the programming for the camera would suggest an exposure that would favor not clipping the highlights on the right side of the histogram. That would surely mean letting in less light so that Shiva would be under-exposed.
The histogram of Shiva’s picture shows clipped highlights on the right represented by the loss of detail in the white sheets she is laying on.

The ‘right’ exposure for any scene is actually quite arbitrary.

And that’s where most folks falter.

The correct, proper or right exposure depends wholly on what your subject is.

Until you, the photographer decides what your subject is, the histogram is just a guide for you to get a best guess to capture the entire scene.

My cat Shiva

Try this: pick a super contrasty subject. something dark against a light background or vice-versa.

In my case, I picked my cat Shiva against her favorite sheet.

The proper exposure or correct exposure if you asked the engineers according to their histogram would yield an image very different from what you see below.

The clipped highlights on the right portion of the histogram is irrelevant in the picture of Shiva.

Since she is my subject, I want to make sure I get a good exposure on her, maintaining the dark coat and saturation in her stripes.

 My Screen door

Early morning sun illuminating my front door screen door makes it very eye-catching and striking but when left on automatic exposure mode, yields a washed out image.

Notice how the automatic exposure gives a decent image but it also allows you to see my neighbor’s car in the driveway?
The histogram shows the bellshaped curve and no clipped shadow or highlights, probably how the engineers intended for good exposure by the numbers.

I didn’t actually have a problem with the exposure suggested by the camera on automatic on my Canon Powershot G11.

I just felt like I could do better, that’s why I went ahead and intentionally under exposed changing the shutter speed from 1/4 sec to 1/25 sec (almost 3 stops) some more so that you can’t see any detail outside my screen door.

Notice the shift of the histogram to the left or the shadow area due to under-exposure? I like this version of the picture better.

Under-exposing by 3 stops prevents my neighbor’s car in the driveway to be seen, but dramatically emphasizes the pattern and graphic elements of my screen door.As far as exposure goes, I like the darker version but I included more to the picture to make it more interesting.

Foggy Lake

Lake Evans on a foggy morning before the fog burns off.

And finally what happens when you have a really low contrast day which is very foggy, what can you expect?

There aren’t any shadows to speak of and there is barely any bright highlights, so in that instance you can expect all the data right in the middle of the histogram.

The next time you’re out and about shooting before you hold up your camera to shoot, visualize if you can what sort of histogram you’ll get before you push the shutter button.

It may help you think carefully about how you expose for your subject.