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Haven’t posted in ages, too many irons in the fire me thinks. I am going to show a very simple method of enhancing the existing colours in a digital photo using GIMP. This tutorial is aimed at those who are new to GIMP and new to photo editing. This is based on GIMP version 2.6.4 and requires no additional scripts or plug-ins beyond the basic default installation.

Here’s a picture I took while out walking the dog one day, some rather sorry looking birch trees. My aim is to enhance the Yellows to give a nice autumnal feel and also to give a boost to the Greens, so let’s begin.

1. Open your image and from the Colors dropdown menu select Colors > Hue-Saturation…

2. Select the Yellow radio button and move the Saturation slider to the right to increase the stauration, in this example I have increased the saturation of the yellows by 20 as I felt that it suited this image.

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3. Select the Green radio button and again move the saturation slider to the right, this time I have increased the saturation by 30. When you are happy with the results click OK.

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Well that was easy, I rarely use the Hue and Lightness sliders so I am not going to take the time to explain what they do, but feel free to experiment with them or check the GIMP Help, if you haven’t installed the Help system they are all available on http://www.gimp.org

The Hue-Saturation tool really is quite useful, some possible ways you might use this tool of your own photos include enhancing blue skies, enhancing reds and yellows in sunsets, reducing red in faces (particularly sunburnt one’s). This list of possible uses is really only limited by you imagination. Here’s an example in which I have used the Hue-Saturation tool to desaturate everything but Blue.

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Happy GIMPin’

T.

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We are all familiar with the dreaded Red Eye in photographs. Fortunately most photo editing applications (GIMP included) have a Red Eye tool built in. Unfortunately most work by detecting red and working from there and hence fall flat on their collective faces when confronted with the green eyes which photos of dogs and other pets can be afflicted with.

This was exactly what happened to me today, anyway after some trial and error I came up with this method, it may not be perfect but it might be of some use in those situations where conventional Red Eye tools fail. Another option of course would be to select the offending colour and minimise it’s effect using the Channel Mixer tool, but I find this to be finicky process and I normally only end up changing the colour rather than elimenating it.

This photo of Lal was taken shortly before she died, she was a diabetic and the cataracts, which are a very common symptom of the disease, have caused a particularly nasty green eye effect. In this case I started by opening my file in GIMP and…

 
1. Zoom in on one of the eyes and select the Fuzzy Select Tool from the Toolbox and click on the eye. You will need to adjust the Threshold value until the entire green area is selected, In this example I increased the Threshold to 100. One thing I like about this method is that it does not matter if any catch lights are selected.

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2. There is normally a small rim of colour just outside the area we selected. We can enlarge the selected area slightly by going to the dropdown menus and selecting Select > Grow… In the resulting dialog box choose to grow the selection by 1 pixel and click OK (you may need to use more in some cases)

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3. To get rid of colour select Colors > Desaturate… Choose a desaturation option and click OK. I have used the Lightness option in this case because it produced the darkest result.

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4. Launch the Curves tool by selecting Colors > Curves… Then darken the selected area by using your mouse to grab the center of the curve and drag it down and to the right.

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5. Use the Clone tool from the Toolbox to fix any odd reflections there may be in the eyes, in this case reflections from Lal’s cataracts. (This step will be unnecessary in the majority of cases).

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6. The transition between the selected area and the rest of the image will often be too “hard”,  select Select > Grow… and this time enlarge the selection area by 3-5 pixels (or whatever suits your image) then select OK.

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7. To do the actual softening use a gaussian blur. Select Filter > Blur > Gaussian Blur… I used the default of 5, then select OK.

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8. Your eye should now be done, turn off the selection with Select > None and repeat the process for the other eye.

 
Happy GIMPin’

T.

 

I have been a long time admirer of toned Black & White photographs. I recently read a book on this subject to see it I could use any staining techniques on digital prints (I see some tea and coffee staining experiment sin my near future). This book introduced me to the fact that some toners work from the highlights to the darks and some work from the darks to the highlights, so I thought to myself that this was a principle which I might be able to replicate in GIMP. I call it Quick N’ Dirty, as it is not an accurate representation of real wold toners, but it does produce an interesting image, in my humble opinion.

 

The original photo is of Cullahill castle in County laois, Ireland. It has had a quick “Auto Levels” adjustment but is otherwise unchanged. Persoanlly I didn’t much care for the colours which seemed oversaturated to my eye.

 

1. From the “Colors”menu select “Desaturate”. As you can see I have used the “Average” option here, but feel free to experiment.

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2. From the “Colors” menu I next select “Curves”. On the “Value” setting I noted that the Histogram suggested slight underexposure, as such I dragged the top of the left slightly.

 

3. In order to simulate a green toner acting from the darks toward the hightlights I once again opened the “Curves” dialog. This time I selected the “Green Channel”. I mouseclicked in the centre of the curve (Straight line at this point) to add a n anchor point, I then dragged the bottom half of the curve upward to add green to the darker tones.

 

4. In order to simulate a blue toner acting from the highlight to the darks I again opened the “Curves” dialog and this time I select the “Blue Channel”. I again added an anchor point in the centre, but this time I want to drag the top half of the curve upward to add blue to the highlights (the sky in this case). Note that the curve is not as smooth as the one I used for green, this is because I noticed that the darker area in thetop left corner of the phot was not being affected, so I skewed the curve a little to counteract this.

 

5. I was going to call it a day at this point, when I asked myself “how would a more purple sky look?”. So back to the “Curves” dialog again, select the “Red Channel”, add a central anchor point and drag the upper portion of the curve upward to add a little red to the highlights. That’s about it, Sharpen and save it off. This effect may not be everyone’s cup of tea but I like the resulting image and it was fun to do.

 

Happy GIMPin’

T.