How to Enhance Digital Pictures in Two Easy Steps

Editing digital photos to make them look more like the view you saw through the camera lens isn't difficult. Photo editing software will do the work for you. All you have to do - and this is the tricky part - is select the right correction tool from the software's menus.

I use two free digital image editors for almost all my photo editing: Irfanview (irfanview.com) has simple photo editing features that I use for almost all of my photos on Associated Content. My other choice, the GIMP (gimp.org) image editor, gives me more control over the corrections but it's not quite as easy to use.

Look at Illustration One. It's a mediocre digital image of a lion statue at the Palace of the Legion of Honor in San Francisco. The lion is what photographers call "washed out" or overexposed. The detail of the statue's weathered marble isn't apparent, and the shadows aren't as distinct as they could be. It was my mistake: I set the exposure wrong.

A novice would adjust the contrast and the brightness controls in an attempt to improve the picture. This, unfortunately, makes equal changes to the shadows and highlights as well as to the mid-range tones you want to enhance. The trees are already dark enough, and the lion doesn't need to be more washed-out than he is already. Instead of the brightness and contrast adjustments, you need to adjust the mid-range tones, then enhance the detail. These controls are usually called "Gamma correction" and "Sharpening" or "Unsharp Mask".

Using Irfanview:

From the menu bar, select Image/ Enhance Colors/ and a dialog box will appear. You need to use the Gamma Correction (it's in the right-hand pane of the control window) Grab the "Gamma Correction" slider with your mouse and slide it back and forth. Watch what happens. The whole image will lighten and darken, but the middle tones will be affected more than the highlights and shadows. Drag the slider until you are happy with the results.

Lowering the lion's gamma level decreases the washed-oout look (if your photo is too dark, increase the Gamma). However, he could be even better, so next I will enhance the weathering detail in the marble. Irfanview has a sharpening tool that uses complex mathematics to calculate and enhance the edges of any area that changes color. This makes details more visible. Select Image/ Sharpen and the control takes effect immediately. Illustration Two shows the lion with the Gamma and the sharpening corrections compared with the original.

Using The GIMP:

The GNU Image Manipulation Program, usually called The GIMP (gimp.org), is not quite as easy to use as Irfanview, but you have more control over the results because you can adjust the values of highlights, mid-tones and shadows individually. You can also control the sharpening filter's effects. Of course, it takes more time to do this.

From the menu bar at the top of the image, select Tools/ Color Tools/ Curves. A control window will pop up showing a line running diagonally from lower left to upper right across a graph. Use your mouse to grab the line where it crosses the center lines. Then move your mouse diagonally from upper left to lower right, releasing the mouse and grabbing the line again several times. Watch the image change every time you release the mouse. This has almost the same effect as moving Irfanview's Gamma slider.

Finer adjustments are possible with the curves tool. If you click on the line and release the mouse, you anchor the line. Click on the line where it crosses the first and last vertical line. Now drag the center like you did before. Watch how the tones change, and experiment with anchoring and dragging at different points. I adjusted the curve to correct the lion's color, but the level adjustment line was anchored at the first and last vertical line. This protected the clouds and trees from most of the adjustments. I seldom use them, but the other choices on the Curves tool control individual color channels. Experiment with what they do if you have time.

Then I enhanced the details using Filters/ Enhance/ Unsharp Mask and the default settings. If you want to experiment, try changing the sliders and see what happens to your image. Illustration Three shows the lion with both the Gamma and the sharpening corrections compared with the original.

Which is better, Irfanview or The Gimp?

Illustration Four shows the final corrections by Irfanview (left side) versus The GIMP (right side). The GIMP preserved the detail in the trees better than Irfanview, but the lion looks about the same in both. The GIMP wins by a small margin. Despite this, I won't say one is better than the other, because they serve different purposes. Most of my web images are resized, Gamma adjusted and sharpened with IrfanView, because it does an adequate job in the least time.

I use The GIMP when the results from Irfanview will not be good enough, or when I need to do something Irfanview doesn't do. The GIMP has more tools (filters, adjustments, and fancy effects) than Irfanview. For example, I used one of the GIMP's tools, called "layers", to make the combined before and after images for this how-to article. Illustration Five shows the lion after some advanced editing. I selected parts of the picture and edited them individually. The lion was level-corrected and sharpened. The wall, lawn and road were slightly blurred to make the lion stand out. The trees were level-corrected to bring the color out of the dark blob. The sky and clouds were not edited. The total editing time was about an hour. Making selections is tedious pixel-by-pixel work.

IMPORTANT NOTES:

- Always work on a copy of your original.

- Do not repeatedly edit and save a JPG. The image will deteriorate with every editing cycle. Open the JPG, save it as a TIFF, edit the TIFF, then save it back to JPG for the web.

- These methods will not change a poor photo into a superb one. They are "good enough" for improving web photos and creating family snapshots.

- The best sequence of work is this: resize, adjust color balance, do any other adjustments, and sharpen last.