The Blur radius can be set within a range of 0 to 200 pixels. If it is set to 0, the brush will have a hard edge and the selection will need to be done very carefully, if it is set to 200 pixels the brush will often affect areas of the image outside of the area you intend to adjust.
What should be set is difficult to say. As a general rule, if you are making a very accurate selection then the bleed area should be quite small, while if you are making more general selections a bigger bleed area can be used.
It is a good idea to use a large brush size and larger blur radius to start with – this allows for a quicker selection.
Now start to paint onto your image. The inner circle is the area that will be fully affected by your changes, the Blur radius is the soft bleed area. As you paint, the image will go very bright if +50 was selected for the brightness, or very dark if you set -50. Don’t worry if it looks false to start with – once you have selected the area you can adjust the brightness settings to a more appropriate level.
New areas
You can start a new adjustment area or add to any area at any time simply by selecting that number before you start working.
This would mean, for example, that you could alter the brightness of the background and main subject independently of each other.
If you want to clear an adjustment area completely, press the Undo all button and it'll wipe any adjustments made to that area.
Correcting mistakes
If you make a mistake in painting an area you can remove it by using the Step back button at the bottom of the tool options. It's best to use small painting strokes and let go of the mouse button regularly to create numerous Step back points. This will mean that you are not undoing good work just to remove a small slip at the end.
If you need to remove the area adjustment, select the Adjustment group number and select the Undo all icon. The Redo all icon will then light up to allow you to step straight to the end image – they work in a similar manner to the Step back/Step forward buttons.
Adjustment control sliders
The contrast option allows you to increase or decrease the contrast in the selected areas. It works in the same way as the brightness option and can be used together with the brightness to control the image.
The hue slider is used to adjust the colour balance on the selected area of an image from -30, which adds more green into the colour, and +30, which adds more magenta, whilst the saturation slider takes you from monochrome to full colour.
One thing that does take a little getting used to is that the thumbnail image does not display the changes when you exit the editing image screens. Instead,there is an edited image icon at the top right of the thumbnail image.
Just like all other changes that you can make using DPP, the selected area changes can be removed at any time afterwards from both RAW and JPEG images.
