5. Soft and Strong  ‘Softness’ feathers the edges, meaning that the effect gradually fades as it moves away from the centre, making the effect more attractive in most cases, while ‘Strength’ is how much of the effect is applied. ‘1’ being the maximum and ‘0’ being none at all. Think of it like an opacity slider for the effect.

6. Clear Boundaries  The ‘Detect Edges’ tick box helps limit where the effect is applied: if Aperture detects a hard edge in the vicinity of the area you’re modifying, it’ll assume you don’t want the effect to go over that area and the brush will not go beyond it even if you drag over it yourself. Note that this will limit your brush’s maximum size.

7. The Eye Dropper  With your brush parameters set, it’s time to alter your photo. You can select one of the six default colours in the Colour adjustment tool, but if none match what you need to alter, click on the adjustment’s eye dropper icon. This brings up the Loupe tool if it wasn’t already in view. Use it to select the exact colour you want to change.

8. Altering the Photo  Next, alter the Colour adjustment sliders then click and drag on your photo where you want to modify the colour. Depending on your Mac’s speed, you should see the results nearly instantly. You can then finely tune the parameters to achieve the exact colour you’re looking for.

9. The Same Adjustment  You can switch between the original and the modified image at any time by ticking or un-ticking the Adjustment’s tick box. But what if you need to change a different colour, somewhere else in your shot? In turns out you can add multiple copies of the same tool: click on the Colour Adjustment’s cog wheel and select ‘Add New Colour Adjustment’. 

10. Black and White  If you check an adjustment’s cog wheel button, there’s another brush labelled ‘away’. To use it, let’s work with another tool. Select a different photo, click on the Adjustments pull down menu and select ‘Black and White’. Click on its cog wheel and choose ‘Brush Black & White away’. Notice that the Brush HUD floating window now has the Eraser tool selected.