jdlevy
Aug 12 2004, 01:22 AM
Michael's article on Understanding Histogams might help.
Jack Flesher
Aug 12 2004, 09:46 AM
Height = Relative number of pixels at that given lighting value.
And theoretically, the total area under the curve should equal 100% of pixels -- at least when the entire curve is visible. (Since an entire image may contain only a narrow range of values, the top part of the histogram may run over the top in an effort to render all of the pixels at that narrow value.)
Tim Gray
Aug 13 2004, 06:46 AM
QUOTE (mnogueira @ Aug. 13 2004,05:45)
You should try reading the e-book: "123d". It has a truly good explanation of this with good and clear examples.
A google of 123d and histogram doesn't turn up anything relevant - can you post a link?
mnogueira
Aug 13 2004, 08:22 AM
Here goes: www.123di.com
(I missed the i)
The explanation from Michael is more than suficient, of course, but I found this e-book from Vincent Bockaert to be very helpfull not only in the understanding of histograms.
Hope it helps.
richard b
Aug 11 2004, 10:22 PM
from left to right is shadow to highlight, what then does the height of the graph tell us and what does it mean if the graph goes off at the top of the window?
thanks
Tim Gray
Aug 12 2004, 08:35 AM
good question - I don't recall that Michael's article dealt with the height. I had asked the question before - I was thinking somehow that the area under the curve should somehow remain constant ie:equate to the number of Pixels - (apparently not true) - but I'm still not sure what the height represents. You can manipulate the height during the ACR conversion playing with the various sliders, as you adjust the left/right positioning the height will change as well, but I'm not sure exactly what the vertical axis measures.
mnogueira
Aug 13 2004, 04:45 AM
You should try reading the e-book: "123d". It has a truly good explanation of this with good and clear examples.
In my article on Understanding Histograms, referenced above, I wrote...
It is a simple graph that displays where all of the brightness levels contained in the scene are found, from the darkest to the brightest. These values are arrayed across the bottom of the graph from left (darkest) to right (brightest). The vertical axis (the height of points on the graph) shows how much of the image is found at any particular brightness level.
Michael
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