Camera Techniques - Avoid Clipping
While I set up for a shot, I rely on my camera’s Live View histogram (seen above) - and for one reason only. It is such a good reason that the histogram is something I would not want to give up if I had to give up something. Certainly, I can survive without it and so can you (what did we do before Live View technology, after all?), but the Live View histogram does make a photographer’s life easier.
Why is the histogram so important? To fully understand, it’s necessary to know how to read and interpret a histogram. A histogram is nothing more than data illustrated graphically. In photography, those data come from your digital camera’s sensor which records light coming in through the lens. The sensor is comprised of millions of data collectors or light collectors. When you hit the shutter button, each light collector opens and receives light photons, which are converted to electrical signals. After the exposure is done and the shutter closes, the light collectors close. The camera measures the electrical signal of each light collector and converts them to digital data. These digital data are represented as pixels. Each pixel becomes a data point which can now be illustrated on a luminosity (light) histogram.
Look at the histogram above. It has two parts, the horizontal or X axis and the vertical or Y axis. The X axis is the distribution of tonal values as each pixel represents a tonal value. Tone refers to the light and dark areas of the photograph and has nothing to do with hue (color) or saturation. A good way to illustrate a range of tonal values is to take out the color, represented here by the dark to light tones shown below the graph. You may have heard the term “grayscale” – this is it.
The X axis includes each data point and the location of a point along the axis depends on its tonal value. Always think of the X axis as a continuum of data from one side to the other. Data that fall left of center are dark values, those that fall right of center are bright values. Midtone values are middle values (not too dark, not too bright). Look at the three images below, each with a histogram. Note the difference in histogram distribution among them. You can see that the first image has a very wide continuum of tonal values; whereas the other two show more data to one side of the continuum.
The Y axis illustrates the number of pixels for each tonal value. Look again at the histograms above and note how each one contains high peaks and low peaks. The high peaks indicate a greater number of pixels representing a small range of tonal values, whereas the low peaks indicate a smaller number. The forest image is a great example. Notice the sun reflection which is represented by a small peak on the far right of the X axis. That’s a very bright area, but it comprises a small portion of the image compared to the dark areas. Therefore, much of the data fall to the left of the continuum. Just for kicks, see if you can connect different tonal areas of each photograph to the histogram data.
So why is the histogram so important? I can boil it down to one simple reason, it helps to maintain detail in the dark and bright areas of an image. Period. Detail is lost in dark areas that are too underexposed and bright area details are lost when overexposed. Look again at the white feathers in the bird image above and now look at an overexposed version below. Notice that more data are pushed to the right on the histogram, so much so that some of those data fell off the chart. That’s referred to as “clipping”. When data are clipped, detail is lost and basically you are left with a bright white area having no detail. That’s what happened to the bird’s feathers!
Look at the forest image above again and compare it to the one below where the dark areas are underexposed. Notice the histogram data pushed against the left side. Those data are clipped or lost, meaning detail is lost. The problem with losing detail is you can’t bring it back; it’s gone for good!
When I am shooting in the field, I want to see that Live View histogram for the purpose of avoiding clipping. Let me say that again - "avoid clipping”! In the photo at the very top, notice the small graph - the histogram - on the LCD. My camera also allows me to see it through the viewfinder. Of course, I can always review my images after the fact and make exposure corrections based on the post-shot histogram. But don’t you think it so much easier to get it right beforehand? One shot – done!
To set yourself up with Live View histogram, do the following three things with your camera.
Enable Live View. In one of your camera’s menu, you should be able to turn Live View (exposure preview) on and off. Some cameras have a dedicated button for Live View. Keep in mind, when Live View is enabled, it will use more battery power.
Enable the histogram display on the LCD and if possible, the viewfinder. In your camera’s menu, you should have display options available for the LCD and possibly the viewfinder and one of those options should include the histogram. If you do not have an electronic viewfinder, rather, the viewfinder is optical, you will not have a histogram option for the viewfinder. Check your manual if you are not sure if your viewfinder is electronic. Through the viewfinder or LCD, I like to see the entire image without obstruction. Then, when I need to see the histogram I push a button to make it appear in the bottom right corner. When I don’t need the histogram anymore, I push the button again to make it disappear.
Check your meter mode. I have a video that explains meter mode if you are not sure about this, so check that out. But, if you are shooting in manual mode, aperture priority or shutter speed priority, you must choose the mode in which your camera meters a scene. I have mine set to evaluative or matrix metering all the time. This is the mode that evaluates the entire scene for exposure as opposed to just a portion of it. If you know what is exposed on the screen, you will be able to read the histogram accurately. Since I am metering the entire scene, the histogram will represent the entire scene. If you use something like spot meter, the chosen spot on the screen will be the only part that is represented by the histogram. Regardless of which meter mode you use, you must interpret the histogram according to that mode.
I hope this helps you to understand some of your camera’s technology that are useful tools for creating better photographs. One thing I know for certain, my images are consistently exposed correctly when I am attentive to the histogram data. The advantage of this is I never lose an image to poor exposure and it makes editing much easier and faster because all the details are retained. So, get your camera and do some experimenting with Live View histogram. Thank you for looking on!
If you have any questions, feel free to contact me at email@example.com. And of course, you can receive individualized instructions in the field or using Photoshop by scheduling a workshop with me.