Tech bytes for tea?

Following my 6-part series in Digital Life (The Straits Times)  on basic photo-editing using GIMP, I received encouraging feedback and requests from readers and friends to cover more topics.

One of these was about the various ways of creating selections and vignettes in GIMP. A follow-up article was run on DL after the series. I cover these today and tomorrow for those who had missed it.

Selections for local adjustments

So far, most of the adjustments we’ve learnt have been applied to the entire photo. For example, removing a colour cast or darkening and overexposed snapshot. Such adjustments that are applied to the entire photo are known as “global adjustments”.

Pict 1: GIMP's selection tools are at the top of the Toolbox while the tool options are below.

What if we want to adjust only a small portion of a photo? For instance, we want to lighten only the face of a person standing in the shadows. Lightening the entire photo just to lighten up one face in the shadows could lead to the faces of other people standing in the sun to become overly bright instead.

In these cases, select only the areas in the photo that needs to be adjusted. While those areas are selected, any adjustments applied will be limited to the pixels within those selections. Such adjustments where edits are done only on a specific part of a photo are called “local adjustments”.

As a workflow, global adjustments to the whole photo should be largely completed before commencing on local adjustments on specific areas of the photo.

In GIMP, the tools for making selections are located right at the top of the Toolbox (see Picture 1 and the sidebar on “GIMP’s selection tool options”). Today we try out the most basic selection tool – the Rectangle Select Tool.

Rectangle Select Tool

With the Rectangle Select Tool, simply click in the photo and drag the cursor to form a rectangular selection.

You should see a moving black-and-white dashed line (resembling a single file of marching ants) marking the outline of the selection. The pixels inside the boundary are now selected and whatever adjustments applied will affect only the selected pixels.

Adjusting the selection boundary (and not the pixels inside)

After you have made the initial selection, you can resize the selection to select a bigger or smaller area.

Move the cursor near the sides or corners of the rectangular selection until the cursor turns into a white triangle. Drag the corner to resize the selection boundary.

Pict 2: This demure deer was chewing on an iron chain for tea when I visited in Nara - Japan's ancient capital.

To move the entire selection boundary, move the cursor near the centre of the selection. When the cursor appears as two criss-crossing double-headed arrows, click and drag to move the selection boundary.

Once you have adjusted the selection boundary until it is where you want it to be and of the right size, you can edit the pixels within the selection.

Pict 3: Captions on the photo is illegible unless its background is made lighter for more contrast against the dark text.

In Picture 2, I wanted to place a caption to label where the deer hails from. You can see that any text placed in the photo would be rather difficult to make out against the distracting background (see Picture 3).

Pict 4: The captions reside in its own layer above the photo. Select the background layer first before increasing the brightness.

You can use the Text Tool to add captions. Any captions added will reside on its own layer above the background layer containing the photo.

Using the Rectangle Select Tool, I made a rectangular selection around the captions. Making sure the background layer with the photo (and not the text layer containing the caption) is selected (see Picture 4), I activated the Colors > Brightness-Contrast command from the main menu.

In the Brightness-Contrast dialog box, I increased the brightness of its the selected area in the photo by dragging the Brightness slider

Pict 5: This iron chewing deer awaits you should you visit the Deer Park in Nara.

At about 100, the dark caption became more legible (see Picture 5).

In the final episode of this series tomorrow, we’ll use the Ellipse Select Tool to create simple digital photo frames, as well as vignettes with blurred edges.

GIMP's selection tools are at the top of the Toolbox while the tool options are below.

The tool options below the Toolbox contains options that affect how the selection tools work, such as fuzzy edges and rounded corners for rectangular selections. It also displays the size and position of the selection in the photo.

The “Expand from center” checkbox allows the selection to be made by dragging from the centre of the rectangle or ellipse (instead of starting from a corner).

To make a selection of specific dimensions or aspect ratio, tick the “Fixed” checkbox. For instance, Type 1:1 in the text box to select a perfect square or circle.

To view the selected area better, click the “Highlight” checkbox so that the unselected areas are darkened slightly. The options in the guides dropdown box allows useful guides such as centre-lines, golden sections or the rule-of-thirds grid to be shown within the selection.

For photos with people in them – especially those with close-up shots – sharpening can emphasize the texture and blemishes on the skin and face. Instead, try simulating a soft focus effect.

Pict 1: This photo of a beautiful young lady is from morguefile.com.

Pict 2: The soft focus effect was added in less than a minute to glam up the shot.

To achieve this effect, photographers in the past used to attach special lens filters or even fit stockings over the camera lens. You can, however, emulate this effect easily in GIMP.

Duplicate the background layer

In GIMP, duplicate a copy of the photo by selecting Layer > Duplicate Layer command from the main menu. Change the Layer Mode for the duplicated layer to “Screen”. You can do this by clicking the dropdown box at the top of the Layers dialog and selecting Screen from the list. The photo is brightened up but still in sharp focus.

Pict 3: Duplicate the photo, blur it and set the Layer Mode to "Screen".

The duplicate copy sits above the original photo (see Picture 3). Apply Filters > Blur > Gaussian Blur command to the duplicate copy. Start with the default setting of five and press OK. Don’t worry if the preview thumbnail shows the image in the duplicated copy to be excessively blurred (see Picture 4). The combination of the two layers via the screen layer mode results in a dreamy glow to the photo.

If the effect is not strong enough, apply the Gaussian Blur filter a second time to the duplicated layer. If the effect is way too strong, press Ctrl-Z to undo and then reapply the filter with a smaller setting.

To finetune and reduce the intensity of the effect, reduce the opacity of the duplicated layer. Simply drag the Opacity slider at the top of the Layers dialog. I usually use an opacity of between 60 and 80.

Pict 4: Apply the Gaussian Blur filter on the duplicate layer.

This effect can also be applied to non-portrait photos to add a dreamy atmosphere to the photo.

Adding a sharpened layer

Pict 5: The sharpened duplicate layer should be just above the background layer.

If the features of the portrait (such as the eyes or the lips) becomes too blurred as a result of the effect, duplicate an additional copy of the original photo in the background layer. Select the background layer before activating the Layer > Duplicate Layer command from the main menu

Apply the Filters > Enhance > Sharpen filter to this new duplicate copy. This layer should sit above the background layer but below the other layers created earlier (see Picture 5).

The sharpened layer will add back some sharpness to the edges in the final outcome.

Tomorrow, we’ll use GIMP give portraits a digital makeover.

Yesterday, we removed unwanted objects from photos by cloning neighbouring pixels and painting them over the objects. Today we use GIMP to sharpen digital snapshots.

Digital photos tend to appear not as sharp as their film predecessors because of the way digital cameras interpret the information from the camera sensor. This is made worse when printing out the photos because of the way ink spreads on the printing paper.

Pict 1: This precarious hillclad village is slightly out of focus because the camera had focussed on the overhanging branches instead.

Pict 2: A bit of sharpening can make a big difference when the photo is printed out. Gourdes is one of my favourite villages in Provence, France.

Sharpening digital photos using an image editor on a computer is simple but can make a photo appear more crisp and appealing (see Pictures 1 and 2). In fact, I usually keep the sharpening setting in my camera and photo scanners to the minimum because a dedicated photo editor on the computer can usually do a better job at sharpening photos.

Quick and simple sharpening

Pict 3: A "Sharpness" setting of between 10 and 50 is usually adequate.

Sharpening a snapshot in GIMP is quick and easy: simply select the Filters > Enhance > Sharpen command from the main menu. A “Sharpen” dialog box pops up (see Picture 3) showing a single “Sharpness” slider to control the amount of sharpening to be applied, and a thumbnail to preview the effect visually. Enlarge the dialog box to make the preview thumbnail bigger.

Pict 4: Deliberately pushing the "Sharpness" slider near the maximum can produce a neat colour pencil sketch like effect.

Avoid setting the sharpness amount too high, since this will also sharpen the undesirable noise and grain in the photo and make the photo look garish.

However, for those looking to turn their photos into a colour-pencil-sketch like effect, try pushing the sharpness slider near the maximum value of 99 (see Picture 4).

If you have the time and desire more control over how the sharpening effect should look, go straight to the Filters > Enhance > Unsharp Mask command instead (see Pictures 5).

Pict 5: The Unsharp Mask filter provides more control over how the sharpening is accomplished.

The Unsharp Mask filter actually sharpens a photo – contrary to what its name suggests – and is the tool of choice of the pros. The name and method used is based on a traditional darkroom technique for sharpening film photos – in which a photo is made to appear sharper by superimposing a blurred copy of the photo over the original photo.

Similar to the simple Sharpen filter, an “Unsharp Mask” dialog box pops up with a preview thumbnail of the sharpening effect. There are, however, three sliders, providing finer control over how the photo is sharpened.

GIMP first detects the edges in the photo and sharpens the photo by increasing the contrast of these edges. It lightens the lighter pixels on one side of an edge and darkens the darker pixels on the other side, making the photo appear more crisp than it really is.

The Amount slider controls the strength of sharpening to apply while the Radius slider specifies how many pixels on either side of an edge will be modified for sharpening.

The Threshold slider tells GIMP how it should detect edges. Only adjacent pixels where the difference in pixel values exceeds the Threshold value will be detected as part of an edge to be sharpened. A high Threshold value protects areas of smooth tonal transition from being sharpened, and minimises the amplification of blemishes in faces, water surfaces or skies.

Pict 6: Pushing the "Radius" and "Amount" up can lead to some nice painterly effects.

Although the Unsharp Mask filter avoids accentuating the noise and graininess in the photo, oversharpening will introduce halos around the edges in the photo and make it look unnatural. Details in the photo are also lost because the highlights are blown out into pure white while shadows are muted into black.

Again, don’t oversharpen unless your intent is to deliberately create a painterly special-effects version of the photo (see Picture 6).

Tomorrow, we’ll use GIMP to give portraits a soft focus reminiscent of glamorous celebrity shots.

Pict 4: Choose the "Fuzzy Circle" brush from the dropdown panel in the tool options below the Toolbox

Drag the “Scale” slider in the tool options to control the size of the brush, or simply press the straight bracket keys on the keyboard – “]” to increase the brush size and “[“ to decrease. The cursor shows how big the brush is.

New to digital cameras? Here are some basic settings to get the most out of your camera.

Yesterday, we used GIMP to turn a colour photo into black-and-white, and tinted it with another colour like sepia. Today, we give GIMP a break and go back to basics. I’ll share what camera presets to use in the digital camera to get the best quality photo from the camera – for GIMP to work on.

Having seen what photo-editors like GIMP can do to correct photographic mistakes and enhance snapshots, one may to tempted to become slipshod when taking photos.

After all, GIMP can straighten a crooked photo, crop a poor composition, remove unpleasant colour casts, and darken or brighten an overexposed or underexposed photo.

Later on in the series, we’ll see GIMP sharpening slightly blurred photos and removing lampposts sprouting from the top of people’s heads.

What a photo-editor CANNOT do

However, there IS a limit to what photo-editors can do. As they say, “Garbage in – Garbage out”.

Pict 2: Le'ts examine areas of this photo taken at the Kitano Tenmangu temple in Kyoto.

Even the best photo-editor cannot add in lost details from an overly blurred snapshot, or bring back image quality destroyed by an overly high JPEG compression. The JPEG compression throws image detail away and introduces unsightly colour blobs called image artifacts into the photo.

Neither can GIMP bring back details that were not captured in an overly overexposed or underexposed photo – such as the backlit silhouette of a person against a bright background.

It is also difficult to remove colour noise introduced by a high ISO setting.

Here are some basic camera settings I propound whenever somebody asks me what settings to use for their new digital camera. If you already know these stuff – please bear with me.

Use the maximum camera resolution

Digital cameras allow photos to be taken at lower resolutions. For example, you can set a 12 megapixel camera to capture photos at eight, three or fewer megapixels. This is for photographers who simply want to send the photo via email or share it online and want to upload the photo fast, or who are running out of space on their memory cards.

Pict 3: Using the maximum resolution means that even if you crop a small portion of the photo or enlarges it, there are enough pixels for a sharp print.

Pict 4: Taken at smaller sizes, enlarging the photo or cropping a small portion of the photo can lead to poor quality due to pixellation.

It also allows you to crop a small portion of the photo and still have enough pixels for a good print. Should you need to email or share a photo online, you can still resize the photo to a lower resolution using GIMP.

Use the best quality setting

Most digital cameras store photos as JPEG files. You can specify how much compression to use. High compression results in smaller files but also means poor quality.

Pict 5: Using a low JPEG compression takes up more memory space but results in good image quality.

Pict 6: Using a high JPEG compression takes up less memory space but results in poor image quality.

Turn digital zooming off

Many digital cameras boast the “digital zoom” feature. Disable this feature. During digital zooming, the camera adds image pixels to the photo to make it appear bigger. This reduces the sharpness and quality of the photo.

If the subject really needs to be magnified, use GIMP to upsize the photo. A photo-editor on a computer can do a much better job than the data processor on board the camera.

Low light photography

Low light photography can produce some of the most challenging snapshots to correct. A high ISO introduces colour noise that is difficult to remove even in a photo-editor. A long exposure results in blurring due to camera shake. While the use of flash can result in harsh hotspots from reflections off oily skin.

For still subjects in low light, use a tripod along with a long exposure and low ISO. The low ISO minimises noise and the tripod removes blurring due to camera shake. The long exposure can result in some grainy noise but it’s not as bad as that introduced by a high ISO setting. However, if the subject is moving, the long exposure will result in motion blur.

Tomorrow, we’ll go back to using GIMP to remove overhead cables, branches sprouting from people’s ears and dustbins in the background.