Please explain clipping

[gafl]

I'm in the process of calibrating my LCD using Digital Video Essentials & I can't understand what is meant by clipping in relation to the white levels (contrast.) An internet search hasn't helped either.

An explaination aimed at a 5 year old would be greatly appreciated.

Thanks!

 

[MDS]

Whether applied to audio or video, clipping in general is when the actual value exceeds the maximum allowable value and thus gets 'clipped' or set to the maximum value.

So for white level, if the maximum value is 100 IRE but the actual value would equate to 105, then the value is stored as 100 and you have 'lost' 5 IRE - it won't appear as white as it was intended. This occurs with black level too and is usually related to the difference between studio RGB and PC RGB levels. On one scale 0 is pure black and on the other 13 is pure black. If you are using the scale where 13 is pure black and the actual value is 5, then it will be displayed as 13 and thus not as black as it should be. It is affectionately known as 'black crush'.

 

[gafl]

Thanks so much! That makes sense.

So in relation to viewing a test pattern for setting contrast, in this case the reverse gray scale with ramps, if I'm looking for clipping in white then what am I looking for?