Footprints and compression marks will show where the pile has been disturbed.
The reason why your carpet shows these marks is firstly because the extra-long, luxurious pile will inevitably bend during use and secondly because the sides of the pile appear to be a much lighter colour than when it is viewed end-on. The random disturbance of the pile during use will give corresponding light and dark patches depending on the angle of the pile in relation to where you are standing. This characteristic is an inherent feature of this type of carpet.
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