Histogram stretch

[drumsolo]

I have been playing with levels and curves in Gimp to do a simple histogram stretch by following guides posted on here. One thing I have noticed is that after the first use of curves the histogram becomes stretched and fragmented and not a nice solid bar chart as in all the guides. Any idea what I am doing wrong?

[Bizibilder]

Not enough data! If the histogram starts to look like a comb then you have either stretched your data too far or you need to collect more data ie more "subs". When stretching you need to be very subtle (it took me quite a while to work this out myself!). Don't move the right hand "white point" slider at all. Only move the left hand "black point" slider until it is just not touching the left hand side of the main histogram peak. The middle slider should only be moved a little at a time.

You may have to do several seperate "stretches" of the histogram to get whay you want - called "iterations" by some. ie One big stretch does NOT equal five or six little stretches! Hope this helps a bit.

[drumsolo]

Thanks for the advice. Sounds like I am stretching it too far as I have 20mins worth of data. Am I moving the curve too sharply, not too sure where I should be placing the points.