Remove the Aberration

Chromatic aberration, also commonly referred to as purple fringing, happens a lot. It’s a myth that expensive lenses eliminate the problem although they certainly help reduce it.

It normally occurs in areas of high contrast where you have a bright colour right next to a darker one.

It’s also not always purple: it can be blue, cyan, purple, yellow and it is not always the same colour in one picture.

It is easy to fix and its presence in a photograph can really detract from the image: drawing the eye to where it shouldn't be because of the unnatural colours.  Stock photography sites such as iStockPhoto will reject any image with a hint of chromatic aberration so knowing the right techniques and software to cleanly repair the photograph is crucial.

This picture of The Needles off the coast of the Isle of Wight demonstrates it really well.


If we zoom in to view the picture at full size, you can see the purple fringing on the left and the blue along the right edge:

There are a myriad of ways to get rid of this through post-processing. I’m a huge fan of non-destructive editing: always preserve the original picture; you never know when you might need it. I have also excluded methods which only deal with chromatic aberration of one colour within a picture or which can impact the rest of the colours in the picture.

Below I’ve detailed the two simplest ways to deal with it that maintain the quality of everything else.

The first method uses Lightroom:

1. Go to the Develop section
2. Zoom into your picture to see the chromatic aberration. If possible, try and get onto the same screen an example of all colours of chromatic aberration
3. Scroll the right hand panel down to the “Lens Corrections” section. You’ll see two “Chromatic Aberration” sliders.

4. To get rid of purple fringing, I moved the Red/Cyan slider to the right. Don’t move it too far or you’ll make it worse
5. To get rid of the blue fringing I moved the Blue/Yellow slider slightly right
6. If you have other colours, experiment with moving the sliders left or right.

This is what I end up with:


To make more selective edits, you can use Photoshop:

1. Add a new layer
2. Set the layer mode to ‘Color’. This will enable you to paint over the chromatic aberration with a brush but only change the colour: the saturation and brightness will stay the same

3. Select a colour which you want to paint over the chromatic aberration. This should be a colour to the left or right of the fringing itself, or go for white. (Press i to get the colour picker and then click on part of the picture which contains your chosen colour).
4. Select the Brush Tool
5. Reduce the opacity and flow to 50% each
6. Make sure you feather the brush and the brush size is slightly smaller than the width of the chromatic aberration
7. Gently paint over the chromatic aberration. You will see it turn to your chosen colour. You may need a couple of strokes
8. As everything is being done on a new layer, don’t worry about making mistakes. Just use the eraser to clean up

For this picture, I painted blue on the outside and tidied up some of the rocks with a white overlay:

This is what the final result looks like:

Which method should you use? Lightroom is definitely quicker but you may find it doesn't get rid of everything in which case I'll clear up the worst of it using Lightroom and then Photoshop out the rest of it.

In the eye of the beholder

I recently went to Les Giants de Ciel in Chauvigny, France. It was by far the best ever 'falconry' display I've ever seen with a fantastic variety of birds amidst a spectacular setting.

As is often the case, there were several birds dotted around the grounds and you could wander around and see the birds up close. I was really pleased with a picture of an eagle owl, until on closer inspection I could see myself reflected in its eye.

Before:I tried cloning out the reflection of me using Photoshop and whilst it worked to a degree, there was still a lot of clutter in the background, detracting from the picture. I found the best solution was to burn the pupil area. This darkens the pupil, obscuring the unwanted detail, but doesn't make it an unnatural pure black.

You can do this in a non-destructive manner:

• Create a blank layer on top of your main picture
• Set the layer to be "color burn"
• Set your colour to be black
• Choose a brush with a low opacity to gradually paint over the pupil to achieve the desired effect

Make sure you keep the catch-light.

My burn layer looks like this:

Now, if you want to tidy up your burning, you can reduce the impact by changing the layer opacity, or refine it using the eraser or select a white brush to vary the effect.

The final result (which I think works really well, but I am biased!):

Using the Pen Tool in Photoshop CS3

For isolations or creating masks, this fellow () is your friend! It transformed the way I do isolations and gives you much more flexibility when creating effective masks. With the possible exception of the Quick Selection Tool in CS3 or above, there isn't anything comparable.

But, the pen tool is a pain to learn and understand properly so I thought I would try and put together a few key points which I found the most helpful whilst using it.

Use P to select the pen tool.

Click once to define your starting point. This will place a solid grey anchor point.

Click once and release to create a straight line between your first click and second click.

The solid anchor point moves to your last click position.


Click and hold to create a curved line. As you hold the mouse button and move the pointer your curve will change shape. You will also see two additional 'anchor lines' which define how the curve is shaped. More on these a bit later. Release the mouse button when the curve is in the correct shape (or close to it).

You can repeat this process, creating an outline of straight or curved lines. When you click back on the original starting point the shape will become closed.

You can edit the shape as you go, or create the outline and then tweak it afterwards.


Moving an anchor point
To move an anchor point, hold down the option (cmd) key and click on an anchor point and drag it.

Changing the shape of a curve
Holding down the option (cmd) key and clicking on the path will select it and reveal the anchor lines.

For simple editing of a curve, hold down the option key and click and hold in the middle of a path. As you drag the mouse the curve will change shape.

For more control, the anchor lines are key to how the curve is formed. They can be moved by holding down the option (cmd) key and clicking on the end of the line (which has a small black dot). If you hold down the mouse button over the end of an anchor line and drag, you will move the anchor line and the curve will change shape.

Creating a corner
Few shapes consist entirely of curves. You will likely need some corners in there. Anchor points can either be an angle or part of a continuous curve.

Whilst initially creating our shape, if you clicked and released, you created a straight line and the anchor point creates an angle. If you clicked and dragged, you created a curved line and the anchor point is part of a continuous curve.

When part of a continuous curve, if you move one anchor line, the other moves in tandem with it to ensure the curve is smooth.

To break this relationship, hold down the ALT key and move one of the anchor lines. It will now move independently of the other line and you can create a corner instead of a curve.

Holding down the option (cmd) key and clicking on a path and dragging it will move that part of the path and alter its curve as you drag

Isolation Tips

• Create your path 1 or 2 pixels inside of the shape you are outlining. This will lower the risk of any stray background pixels creeping into your isolation
• Don't feather more than 1 or 2 pixels
• Don't feel you need to use the pen tool entirely to create your isolation. Use a combination of techniques. For example, never use the pen tool for hair!
  
• For a quick isolation, a large depth of field is preferable so the outline of your object is entirely in focus. If the focus changes around the outline you will need to selectively blur the edge of your mask to make it look natural

General Path Tips

• As you create your path, Photoshop saves it under a 'work path'. Save your work path by double-clicking it and giving it a name. It will now be saved with your file. Failing to do this will lose all your hard work!
• You can quickly delete a point by pressing the delete key