2012-11-05

Photo editing - a general workflow

This guide requires the free editing software GIMP, which you can download here, and also some basic understanding of how to use the program. A good idea before following this guide is to check the basic tutorials on the GIMP homepage.

So you have taken the photo and you have transferred it to your computer, and now what? Most people are in possession of a camera, and most people take good, or even great, photos, but very few do anything more with them. Sometimes I have a small memorial for all the photos sitting on peoples hard drives, without being watched or shared. I light candles and there is a lot of crying. So in order to cut my Kleenex expenses, I decided to do a small post on my editing workflow.
Before we start with editing we need to have an image. Preferably a good one. Soon there will be a link to my "take a good picture"-how-to. I hope you already have a good picture, so let us get on with the workflow.

6 Step Workflow

Step 1 - Crop & alignment

This is probably the most important step. Many people, myself included, like to place the object in the middle of the frame. This is great for focusing, but from an artistic standpoint it is really, really, and I cannot stress this enough, really boring! Preferably you should already have thought about placement of your subject in the frame before taking the shot. But sometimes you just want to shot without thinking, and that is where cropping comes in.

When cropping your image you should think about the rule of thirds. For those of you interested in knowing more about it read about it here.

With your photo opened in GIMP click on the Rectangle select tool (or press R). Choose the Tool options dialog and scroll down to where it says No guides. Here you can choose to use Rule of thirds. When you make a selection on your image you will now see two horizontal and two vertical lines. The subject or object should be placed roughly in one of the four intersections created by the lines.



Step 2 - Levels

Next we need to give the image some punch. Duplicate the original layer and rename it Levels. Now go to Colors > Levels and a dialog like this should pop up:

You should note the histogram, and if you do not know how to read an histogram you can read about it here. To the right we have the white arrow (C) showing the point and value of the whitest part of the image. To the left we have the black arrow (A) showing the point and value of the blackest part of the image. In the middle we have the grey arrow (B) showing the point and value of 50% grey.

As you can notice I have changed the position of the arrows and you can do this in two ways. First of all you can click and drag the arrows to the position suitable for the image. Second you can use the eye-dropper tools and click on the image on the parts that are supposed to be black, 50% grey and white.
NOTE! Always be careful that you do not loose any detail you might want to have in the picture. In the above example I am loosing picture information in the bright parts, since all picture information to the right of the white triangle will be lost. This worked for the image I was working on at the time, so always take a look at the whole picture and rely on what you think looks best for a particular picture.

Step 3 - Dechroma & Denoise

This step can be skipped if the image was shot at lower ISO values. If you have trouble with noise in your image there are a few things you can do. I personally have nothing against noise as I think my Nikon D60 produces a nice noise pattern (at least up to ISO800). What I do not like though is coloured (chromatic) noise, and this can be fixed using a small script called Dechroma by jpsutto which can be downloaded here. You will find it under Filters > jp > dechroma. This will get rid of the chrominance, but the noise (and most importantly, the detail) will still be there.

If you are looking for a silky smooth image you can get rid of the noise all together. As tempting as the prospect of a silky smooth image might be, there is always some loss of detail when denoising. The best app used to be GreyCStoration but this has been upgraded into G'MIC which includes two algorithms for noise removal: anisotropic smoothing and patch-based smoothing. Download G'MIC here!

With the layer selected go to Filters > G'MIC... and notice the filter sections with a live preview to the left. Go to Enhancement > Anisotropic smoothing. To be honest I haven't the slightest idea what all sliders do (which the next few paragraphs will show). I apologize for my ignorance. The sliders I use are Amplitude, Anisotropy and Tensor smoothness.



Amplitude: I usually work with amplitudes between 10.00 and 40.00, but it all depends on your image. The higher the number, the smoother the picture. But you also loose a lot of detail on higher settings, so use with care! Always check important parts of your photograph in the live preview box to the left.

Anisotropy: I use this slider to get rid of the halo-effect that occurs in dark or light parts of the image. To get rid of a lighter halo in a dark part of the image move the slider to a smaller value, and to get rid of a darker halo in a light part of the image move the slider to a higher value.

Tensor smoothness: I use this slider to adjust for the noise size. Usually I leave it at it's default value, but when the noise pattern gets bigger I increase it a few steps (e.g. 0.5) to get a better effect.

Step 4 - Colour Boost

This is of course optional, but I like some colour in my images, unless I want a B&W. Unfortunately it is not as simple as dragging the saturation slider to the top. A guide of a better way to increase saturation can be found here. This only increases the saturation in the brighter parts of the image, which gives a more natural look. I would compare this effect to the vibrance setting in Photoshop programs.

Step 5 - Sharpening

In GIMP, especially with G'MIC installed, there are several ways to sharpen your image. I will present the simplest option, and still my favourite: Unsharp mask.

Unsharp mask: I've written about it before and it used to be my standard way of sharpening my images. The filter can be found under Filter > Enhance > Unsharp mask... You can use the default settings, but I usually decrease the Radius from 5.0 to 3.0. I choose a smaller pixel size since I upload my pictures to web. But if you are going to print your pictures a bigger pixel size might be desirable. Adjust the Amount to the wanted effect. You can also use the Treshold slider to change how sensitive the sharpening should be. This is useful if you have noise in your picture, and you don't want it to be sharpened.
Effect of Unsharp Mask with settings: Radius: 3.0, Amount: 0.5 and Treshold: 17
NOTE! It's easy to overdo this sharpening part. When overdone it will create unnecessary halos where there are extreme contrasts (dark subjects agains bright sky, for example).

Step 6 - Vignetting

This step is the last in my editing workflow. It is optional, but amazingly effective in creating some depth in the picture. I've described it before, in relation to landscapes, and how to improve the apparent depth of the scene. This is also very effective in making your subject stand out in the picture.

To get your subject to stand out, create a new layer. Go to Tool Options dialog and choose radial. Check that the foreground colour is white, and the background colour is black (you can switch the foreground and background colours by pressing X on your keyboard).


Zoom out your image quite a bit, click on your subject (or if it's a model, click on his/her face), and drag your mouse to well outside the picture. Let go and the image should fill with a white spot going gradually towards grey. Now click on the Blend Mode and choose Burn. Adjust the Opacity to the wanted effect. This is what my image look without and with some vignetting.


Well that's it! By now you have completed my general workflow. Remember that this workflow isn't the only way to edit photos. It is a rough guide, and don't be afraid of some experimentation!!

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