I have been trying to do this successfully for a while but my endeavours have never looked quite right. Leafing through the March 2006 issue of Photography Monthly I found out that there is a filter in Photoshop that will do the job for you.
What is ‘the job’ you may ask? This is where you want to ‘cut out’ a portion of an image, say a person, so that the background is removed. Performing this task using the selection tool can be a little tricky and time-consuming especially when selecting hair, for example. The way to do it properly is as follows:
1. Select Filters->Extract… from the menu bar
This will open the Extraction Filter dialogue box.
2. Select the brush tool and optionally the brush size
Now click around the area to be cut out. you don’t have to be too accurate when doing this but it may help to magnify the image a little using the magnifier tool before starting. For areas such as hair just make sure the green highlight marker encapsulates each errant strand.
3. When the whole outline is painted with the green highlighter, select the fill tool
Click inside the area to be cut out. This will paint the cut out a purple colour.
4. Select the Preview button
This will show the final result. Here you can choose a white, black, transparent or custom background colour. If the result is not quite what you want then you can use the the Cleanup tool which will subtract opacity from the edge and the Edge Touchup tool that will render the edges sharper and with greater definition.
5. Once you are happy with the result click the OK button.
This will produce the cut out with a transparent background which can then be combined into other layers to create a composite image.