An Introduction to GIMP Photo Editing

If you’re new to the app, it’s easy and intuitive to pick up; you can get excellent results in no time at all. If you’ve used Photoshop before, you’ll find GIMP familiar. There are some different features, and the tools often have different names, but the basic principles are the same.

Before You Begin

Before we look at how to use GIMP for photo editing, there are a few things you need to know:

  • The default setup for the app is for every part of the interface — all the panels and toolboxes — to exist in their own window. To make it function as a more traditional program, go to Windows > Single-Window Mode.
  • Images tend to open in a zoomed out view. To set the image to a more appropriate size go to View > Zoom > Fit Image in Window.
  • GIMP does not support non-destructive editing. Any edits you make to a file will be permanent. For this reason, always work on a duplicate copy of the file with the untouched original stored safely.
  • Also, consider applying all your edits to duplicate layers within the image (right-click the layer in the Layers panel on the right and select Duplicate Layer). You can then delete the layer if you want to remove that edit later on.

GIMP download page

Straighten the Horizon

Getting the horizon askew is one of the most common mistakes in photography, and also the easiest to fix. And unless you’ve deliberately shot your image that way for artistic reasons, it’s the one thing you should always correct.

Select the Rotate tool from the Toolbox in the left hand column, or press Shift + R. In Tool Options below that, set Clipping to Crop to result.

Now click anywhere in the image to open the Rotate box. Next to Angle, click the up and down arrows to rotate the image. Each click turns the image by one-tenth of a degree. You can type your own number in the box if you want it even more finely tuned.

Straightening the horizon by rotating in GIMP

When you’re happy click Rotate. The image will now be rotated and cropped to shape. Finally, go to Image > Autocrop Image to remove the transparent areas that will have been left around the edges of the canvas.

Crop Your Photo

Cropping is an effective way of tightening up a photo’s composition or removing unwanted objects around the edges.

Select the Crop tool (Shift + C). Now click and drag inside the image to draw the outline of your new crop. Hold the Shift key to maintain the photo’s original aspect ratio.

Cropping a photo in GIMP

To adjust your selection, hold your mouse in the corners or edges of the frame and then drag in or out to correct. Alternatively, click in the middle of the frame and drag to reposition the cropped area. Hit Enter to confirm.

If you’re cropping to improve composition, experiment with the composition guides in the Tool options. This enables you to overlay a rule-of-thirds grid (learn more about the rules of composition in photography) to aid with your crop.

Improve the Exposure

When your photo is too light or dark, or contains blown highlights where the brightest parts of the frame are rendered as pure white with no detail, you need to fix the exposure.

Brightness-Contrast in GIMP's Colours menu

Go to Colors > Brightness-Contrast, then drag the Brightness slider left or right until you find a level you’re happy with. Toggle the Preview button on and off to see the before and after effect, then hit OK to apply the changes.

Adjusting brightness and contrast in GIMP

When you’re working with JPEG files, you should try and keep the exposure tweaks fairly subtle or you’ll risk introducing noise or otherwise degrading the image.

Correct the White Balance

White balance is used to remove an unrealistic color cast from an image. While it may seem obvious that a white area within an image should look white, sometimes the camera can be thrown off by ambient lighting conditions. Under certain artificial lights, for instance, the image may get an orange hue — or under cloudy skies it may look blue.

Automatic white-balance correction in GIMP

To fix this, go to Colors > Auto > White Balance, and it should be instantly corrected.

If you aren’t happy with the automatic results, there’s a manual option you can try. Go to Colors > Levels, and toward the bottom of the window that opens click on the middle eye-dropper icon. This will enable you to set a gray point in your image, an area of neutral color off which all the other colors will be based.

Choosing a neutral gray for white balance in GIMP

With the eye-dropper selected, find an area of gray in the photo and click on it. The color of the photo will update in real time. You can experiment with different grays in different parts of the picture until you find one that you’re happy with.

Tweak the Colors

Most photos can benefit from tweaking the colors. Photos with bright, vivid colors often get a strong reaction on social media, but you can also create more subdued colors if that suits the effect you’re going for with your photo.

Start by heading to Colors > Hue-Saturation. You can boost the colors across the entire image with the Saturation slider. Beware that it’s very easy to oversaturate your images, so take it slowly. A good rule is to set the saturation to a level that looks okay, then just drop it back a little.

To get even more control you can adjust the red, magenta, blue, cyan, green, and yellow parts of your image separately. Here, the Lightness slider becomes more important than the Saturation slider.

Adjusting hue, lightness, and saturation in GIMP

For example, to make a sky look bolder and bluer focus on the blue and cyan colors, and set the Lightness slider to a darker level. Or to make grass and foliage look greener and more vivid, increase the Lightness level for green. If you’re left with harsh edges around the areas of color that you’ve adjusted, drag the Overlap slider to the right to help blend them better.

Add Contrast

The simplest way to add impact to a photo is to boost the contrast. It can often turn an otherwise flat image into something packed with drama. The best way to do this is with the Levels tool, which you can open at Colors > Levels.

This opens the Levels dialog box, with a histogram (labelled Input Levels) in the top half. This graph shows the tonal range of your image: black on the left, white on the right, and all the shades of gray in between.

Adjusting the histogram in GIMP

All you need to do is drag the handles below the histogram inwards until they’re in line with the first clump of pixels on the left and right edges of the chart. This sets the darkest point of the image to 100 percent black, and the lightest point to 100 percent white, and maximizes the contrast in the process.

Remove Dust

GIMP has a quick and easy tool for removing specs from an image caused by dust on your camera’s lens or sensor.

A speck of dust on an image

First, zoom into your image by going to View > Zoom > 1:1, or by hitting 1 on your keyboard. You can scroll around the image by holding the spacebar and then clicking and dragging with your mouse.

Next, select the Healing Tool (H). Use the square bracket keys ([ and ]) to adjust the size of the healing brush so that it matches the size of the speck you want to remove.

Using GIMP's Heal tool to fix a photo

Hold down Ctrl on Windows, or Cmd on Mac, and then click an area of the same color right next to the spot you want to remove. Then release the Ctrl or Cmd key and click the spot. It should now disappear, or you can paint over it a little more until it’s gone.

Selecting two areas for healing in GIMP

What you’re doing is telling GIMP to copy the pixels from the first click and paste them on top of the second (the speck of dust). It then blends them seamlessly and naturally.

Repeat this for all the unwanted spots on your image.

Doing More With GIMP

These steps will take your photos from their rough, straight-out-of-the-camera state, to something that you’ll be proud to print or share online.

  • Explore third-party plugins that help with noise reduction and sharpening.
  • Learn the Curves tool to gain greater control over the color and tone of your images.
  • Discover Masks, which make blending multiple images easy.
  • Learn to use the Clone and Airbrush tools for the most advanced levels of photo retouching.

GIMP is a very powerful program that excels at photo editing. By learning how to use it you’re well on your way to making your photos look better than ever.


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