PixInsight Forum (historical)

PixInsight => General => Topic started by: andyschlei on 2007 April 10 16:41:07

Title: Shadows Clipping >100%?
Post by: andyschlei on 2007 April 10 16:41:07

I was just working with a star mask and trying to drop out the background that remained after my initial aTrous wavelet transform, and I am having a some confuction working with the histogram.

At high bit counts (16) it doesn't really show any values, even stretched to 20x vertically.  I used a lower bit count.

Then when I went to clip the shadows, and the bit % quickly went over 100%.  So this is my question:  What does that % represent?  Is it the percent of shadows?  How are shadows defined -- Pixels below the median value?

If the latter, I would suppose the shadows clipping percent = # pixels clipped / 50% of total pixels (assuming no midtone adjustment).  Does the midtone adjustment affect the %?

I am sorry for all the possible silly questions, but I assumed the % was the % of total pixels being clipped.

Thanks in advance,

--Andy

Title: Shadows Clipping >100%?
Post by: Carlos Milovic on 2007 April 10 20:33:01

Hi Andy

I guess that you are working with a Color image, modifiying the RGB/K channel at the HistogramTransform window. If so, the percentage of pixels goes up to 300%, becouse all the channels are counted (3x 100%).


:)