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Photo Editing Basics, Part 3 – Brightness Levels and Color Balance

Photo Editing Basics, Part 3 – Brightness Levels and Color Balance

We all strive to take the perfect photos but very often we manage to get the incorrect exposure resulting in our photo being too light or too dark. Often, a photo will look fine on the viewer in your camera but when you download it to your computer or into your photo gallery, the flaws reveal themselves. A common fault in photos is an incorrect White Balance resulting in photos being too yellow, orange or blue.

Brightness levels

The Original image and the Corrected image showing its histogram.

Xara Photo & Graphic Designer includes fast, easy to use photo editing tools that can help you to color correct your photos easily. I’ll show you how, so download the trial version of Xara Photo & Graphic Designer and try it!

This tutorial will focus on editing the whole picture – a later tutorial will show you how to make regional changes. Below is the Photo Tool with its fly out menu. We’ll start with the easy slider controls in the Photo Enhance Tool so click the Camera icon.

Photo Tool Bar2

From here you can adjust the Brightness and Contrast, as well as the Color Saturation, Color Temperature, Hue and Blur or Sharpen. Simply enter a value or click on the arrow alongside the function to open up the slider control. For example, if you increase the contrast, the brighter parts are brighter and the darker parts are darker and vice versa.

At any time you can click the ‘Compare’ button on the Photo Tool InfoBar to compare your changes with the original. Click it again to revert back to the current settings (this toggles between the original and current) Don’t forget you can use the undo to remove the last settings, so experiment as much as you wish.

There is a much more powerful way of viewing and manipulating brightness levels by using the Histogram and Levels feature. Select the Levels Tool to open the Brightness Levels Dialogue and you will see a histogram for your photo. The histogram counts the brightness levels of every pixel in the picture and draws a graph to tell you where those pixels are on the scale of dark to light. The graph looks like mountain peaks and gives you an ‘at a glance’ overview of the brightness levels of your picture. The left side of the histogram is dark, the right side is light, and the middle is the mid-tones.

The aim is to get a histogram with a good range of shades from dark to light that matches the scene you are shooting, so a night-time shot would be heavier on the left, a landscape would be in the middle and a snowy scene heavier on the right. You also want the ‘mountain’ slopes to go to ‘sea level’ on each of the far ends of the graph. The Levels dialogue works in conjunction with the Brightness and Contrast sliders so you can use both sets of controls together or separately. The best way to see how this works is to look at some examples so you can see what we are aiming for.

Brightness levels1

This is a good example, you can see that the histogram has a well dispersed range of peaks touching the ground at both the black and the white ends, ie over the entire brightness range of 0 to 255.

Snow1

This is a classic example of a camera doing what it thinks is right – trying to expose the large area of white so it’s approximately in the middle of the brightness levels. Instead of the brightness levels being spread over a 0 to 255 brightness range they are compressed, with almost no bright pixels at all. However, this is snow and it should be much lighter than this.

For this reason, some cameras have a special ‘snow’ pre-set where they compensate. When you are not using the pre-set, despite being counter-intuitive, it’s better to over-expose snow pictures, rather than under-expose them. You might be thinking there’s so much bright white that you should under-expose, but that’s wrong. By over-exposing, you compensate for the camera’s tendency to over-darken large areas of bright whites.

Snow2

We can fix this picture by adjusting the Histogram. Firstly, I dragged the white point input (small white triangle under the histogram) to the right end of the histogram (new value 173). What this does is re-distribute the brightness levels that go from 0 to 173, right across the whole brightness range.

The snow is now significantly more realistic, but the result still has too much contrast, and the subject’s face is too much in shade. So I will now adjust the center brightness control (which is actually a gamma control) in this case, to a value of 1.60, which further lightens the dark to mid-tones. Note that this causes a bulge in the green levels curve (the bulge at the left end means its only brightening the darker shades, and not the lighter shades).

Snow3

This is the finished result. The histogram now shows both the original (dark red) and the new histogram (pale red overlay) with the peak on the chart moved to the right end which is exactly what you’d expect of a picture that’s predominantly snow. The resulting picture is dramatically better. Clicking the Compare button on the Photo Tool InfoBar allows you to rapidly toggle between before and after comparison.

Temple1

This image is dark and the histogram reflects that. It doesn’t mean it’s under-exposed, just that the image contains a lot of dark areas. It still has a good distribution of brightness levels because you can see that there are shades covering the whole range, albeit very slight on the light end. The white balance is perhaps questionable – it’s a very orange image – but that’s because they are gold painted Buddhas in a dark temple, lit with incandescent lights and candles.

Temple2

There’s not much that can be done to improve this image. However, I have adjusted the white point down to 236, and also given it some slight brightening of the low to mid shades by dragging the gamma to 1.14. Finally, I have adjusted the white balance by dragging the grey ‘eye dropper’ icon from the histogram dialog over a grey part of the image (the room background). You can see this has improved the detail and colors of the garments.

White balance
White balance is the process of getting the colors in your images as accurate as possible. All cameras have some basic white balance settings such as Auto, Tungsten, Fluorescent, Daylight/Sunny, Cloudy and Flash, but many amateur photographers do not use them or quite commonly, forget to change them back when moving from one scene to another, resulting in images that are too yellow, orange or blue. The levels dialogue allows you to adjust the overall colour balance, in particular, the white balance so you can improve the photos that have been taken with the wrong settings on your camera.

Tibetans1

The white balance for this image was incorrectly set for interior incandescent light as it was not reset to daylight when returning outside – the result is a strong blue cast to the whole image.

The histogram show a good range of shades, but lacking at both ends, with not many really dark or really light shades, which corresponds to a lack of contrast.

Tibetans2

I’ve moved the black and white points to the ends of the histogram to re-distribute the shades. The largest change is achieved from adjusting the white balance by dragging the grey ‘eye dropper’ onto a grey object (I used the man’s hair). As you drag the dropper over your picture you can see it changing, sometimes dramatically, as it looks at the pixels under the mouse pointer and tries to adjust the balance of the whole picture so that the pixels under the picture are grey.

You can see that the garment and face colours are slightly better, but it’s probably impossible to get a perfect colour balance when the photo is so wrong in the first place. I’ve also cropped it to try and improve the composition and I’ve sharpened it. The resultant image is a significant improvement, even if it’s far from perfect.

The Curves Control
Some software have a separate ‘Brightness Curves’ dialog that also lets you adjust the brightness levels. Xara combines this ‘curve’ control into the same dialog – it’s the green line you can see drawn across the histogram.

This green line represents a mapping of input shades to output shades.  So a straight line, from bottom left to top right, means that there’s a 1:1 mapping. In other words, blacks convert to black and whites to white, and a brightness level of 128 is 128 ie. no change.  As you adjust the brightness slider on the InfoBar (or the middle grey small triangle under the histogram which does the same thing) you will see that the green line bulges. (You can see this in the above screen shot). What this means is that the darker shades are being lifted slightly. If you adjust the Contrast or the black or white points you can see the green curve change to reflect the new mapping curve.

But it goes further than just showing the curve as a green line – you can drag on the curve to create any brightness mapping curve you like. This is an immensely powerful way of adjusting the brightness levels of pictures.  As a simple example here’s one where I have dragged on the curve in two places to create a new mapping curve (the pale blue line).

histogram 1

You don’t need to see the picture to understand what this does. By lifting the dark end, and dropping the bright end, I have in effect reduced the contrast of the image and you can see this reflected in the histogram. Actually, there was nothing wrong with the original brightness levels – they were well centered and with a good distribution, but you can see the new histogram (the pale overlay) results in less contrast – that is fewer dark and fewer light shades.

In this second histogram, I’ve done the opposite – moved the dark end down (made the darker shades darker), and moved the lighter end of the curve up.

histogram 2

The new histogram is now more spread over the brightness range giving brighter whites and darker blacks, in other words a high contrast image. You can see this degree of manual control allows you to adjust any part of the brightness range without affecting other parts. So you could, for instance, darken really bright parts of the picture, but leave all dark and mid-tones as they are.

I’ve only touched on some of the capabilities of the Histogram Levels and Curves tool, but it’s worth mastering as a very powerful, fast and interactive way to adjust image brightness, contrast and white balance levels, all in one dialog.

See Photo Editing Basics Part 1 – Formats and Sizing
and Photo Editing Basics, Part 2 – Creating the Perfect Photo

Xara’s unique non-destructive nature maintains the high quality of your original photo regardless of how many times you open-edit-save it. As a result many people use Xara Photo and Graphic Designer as their primary, general purpose image and document composition tool.

Download Xara Photo & Graphic Designer and try it!

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