Friday, July 26, 2013

Understanding Camera Histograms in Photography







It took me a while after switching to digital photography, to fully understand the histogram. Now, for me, it’s an essential tool in determining proper exposure in my photography.

Most all cameras today can display a histogram. From the least expensive and simplest point and shoot to the most sophisticated professional camera, they all have the capability to display a histogram after you’ve taken the picture. Some cameras with electronic viewfinders will display the histogram live, even before you press the shutter.

Professional cameras will even display a histogram showing the three color channels, red, green and blue, (RGB), in addition to the luminance histogram showing the brightness of all the color channels together.

So what is the value of viewing a histogram? To me, it is everything. It is how I determine the proper exposure of every picture I take. But I’m a serious professional photographer.

Most serious amateurs, if they understand it, will take advantage of their histogram. But do those of you who simply want to have fun taking pictures of their friends, families and vacations need to consult the histogram? Not really. Modern-day point and shoot cameras and consumer level digital single lens reflex cameras, DSLR’s, do a great job producing good exposures and beautiful photos. But it never hurts to have a little understanding of such a deceptively simple yet potentially confusing camera function.

As I said above, it took me a while to understand the thing. There was nothing even remotely resembling it on film cameras and it was not something that anybody taught. My switch to digital would have gone much smoother had I understood it from the beginning.

So here it is, in all it’s simplicity.

Essentially, the histogram is my light meter. Because of it, a lightmeter is one piece of equipment I don’t no longer have to carry. Now that is heresy to some, but so be it. My life is simpler without having to take a lightmeter reading of every photograph I’m about to take.

Here is an example of what a good histogram looks like:



Here is an underexposed histogram:



And here an overexposed histogram:



That’s it, that’s all you need to know.

But then, of course, there’s more to it. Fundamentally, you don’t want your histogram to be climbing the walls. That is to say, the left side of a histogram shows the blacks and shadows in the scene. The right side show the whites and highlights.

If your histogram is climbing the left wall as in the underexposed histogram above, then you’re blocking up your shadows, i.e. there will be no detail in your shadows. If it’s climbing the right wall like the overexposed example, your blasting out your highlights. Again, no detail. And with jpegs, no possibility of getting the details back.

Here are photographs to go with the above histogram examples.

Good exposure:



Underexposed:



Overexposed:




And what are all those peaks in the histogram? They simply say that at that particular brightness level, the camera sensor is picking up more pixels. In other words, the scene you’re shooting is made up more of a particular shadow or brightness or mid-tone than other brightness’s. 

But that’s confusing the issue. All you need to know is whether you have a fairly even distribution across the histogram without blocking up the shadows and/or blasting out the highlights.



Copyright 2013 Dennis Jones/Dreamcatcher Imaging
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