Gimp part 3

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IMAGE MANIPULATION


The Gimp: Photographic techniques


The Gimp's tools are perfect for working with photographs, and going from average photos to studio-quality images requires only a few simple techniques, as Michael J Hammel reveals...

CREDITS
All photos are taken from the public domain collection at www.pdphoto.org

We aren't all professional photographers or graphic artists. However, while we may not have the $5,000 cameras that the professionals use, we do have the same software tools that are available to those people, and there are many common techniques for using this software. Learning to create good selections is a big part of working with photographs, as are layer masks and blend modes. And how could any graphic artist worthy of the name get away without at least one good blur a day?


In this tutorial, we're going to look more closely at three techniques that graphics experts use a great deal: depth of field, simulated motion and reflections. All of these are a lot easier than they might first appear, so don't fret ­ just practise and play. It's how all graphic artists get started. Take a look at any of your personal photos. If most of your shots were taken with a typical disposable camera, you'll notice that there's a
One-gimp-63.png (http://www.linuxformat.co.uk/wiki/images/1/1c/One-gimp-63.png)1/ The original 1,024x768 image is clear and crisp, but the focus of the photo is the room as a whole. The goal is to emphasise just the table and chairs, so create an oval selection around the table (it doesn't have to fit it exactly). The selection is feathered by a large amount ­50 pixels in this case, although it could have been more. Invert the selection and run Gaussian Blur, set to about 5 or 10 pixels. To add more emphasis, add a new layer (with the selection still intact) and fill with a Radial gradient, white to black, centred in the selection. Reduce the opacity of this layer and set the Blend mode to Multiply (for The Gimp 1.2) or Grain Merge (if you have version 2.0).
wide depth of field. That means that, assuming your subject is more than a few yards away, pretty much the entire photo is in focus. Changing the apparent depth of field can alter the subject of the photo. If you're subject is off-centre and not completely obvious, a depth of field change can pull the subject out, exposing the true meaning behind the shot.

In reality, a depth of field trick is no more than a selective blur. You've seen this trick numerous times in advertisements for cars, with the car in focus but the background blurred out of recognition. In the first example, I'll use a variation on depth of field effect to pull one area of an image into the spotlight. The second example pulls a building to the forefront of a photo, with true depth of field changes.

Two-gimp-63.png (http://www.linuxformat.co.uk/wiki/images/a/a4/Two-gimp-63.png)2/ The first example wasn't a true depth of field effect because it's easy to see that the other objects are at the same distance from the viewer as the table. This example is more true to depth of field. The

original image is mostly in focus but with an obvious foreground object, the outhouse. Use Quick Mask to create a selection around that and some of the grasses below it, then save the selection to a channel. Now feather, copy and paste the selection as a new layer.

A more professional shot can be made from an ordinary still photograph by applying a motion blur to the object of interest. In this next example, the final effect is actually the easy part ­ the trick is in pulling the object out of the background in order to apply the effect only to the subject. It's important to note that techniques like this one work well with non-linear and distant backgrounds, like mountains. If edges need to line up exactly, then cloning, as done here, doesn't work as easily to remove an object from the background.

Again, trial and error will see you through with this technique. Try to experiment on a smaller version of an image to see if the basic technique will work before trying it on larger scans. Another simple effect that anyone can do is to simulate the reflection of an object on a glassy surface. This technique is easy but requires a good subject in order to obtain the best results. In this example, we're using a yellow rose. Objects that can stand upright in the image, such as the head-on view of a mobile phone or a car seen from the side, offer the best results, especially if you want the reflection to be recognisable. Objects that provide fewer straight edges or flat sides, like this rose, are better suited to reflections that are rippled and distorted to make them less recognisable.




CREDITS All photos are taken from the public domain collection at www.pdphoto.org