Luminous Landscape Forum

Equipment & Techniques => Digital Cameras & Shooting Techniques => Topic started by: jdlevy on August 12, 2004, 02:22:38 am

Title: histogram
Post by: jdlevy on August 12, 2004, 02:22:38 am

[font color=\'#000000\']Michael's article on Understanding Histogams (http://www.luminous-landscape.com/tutorials/understanding-series/understanding-histograms.shtml) might help.[/font]

Title: histogram
Post by: Jack Flesher on August 12, 2004, 10:46:51 am

[font color=\'#000000\']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.)[/font]

Title: histogram
Post by: Tim Gray on August 13, 2004, 07:46:10 am

Quote

[font color=\'#000000\']You should try reading the e-book: "123d". It has a truly good explanation of this with good and clear examples.[/font]

[font color=\'#000000\']A google of 123d and histogram doesn't turn up anything relevant - can you post a link?[/font]

Title: histogram
Post by: mnogueira on August 13, 2004, 09:22:48 am

[font color=\'#000000\']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.[/font]

Title: histogram
Post by: richard b on August 11, 2004, 11:22:30 pm

[font color=\'#000000\']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[/font]

Title: histogram
Post by: Tim Gray on August 12, 2004, 09:35:56 am

[font color=\'#000000\']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.[/font]

Title: histogram
Post by: mnogueira on August 13, 2004, 05:45:40 am

[font color=\'#000000\']You should try reading the e-book: "123d". It has a truly good explanation of this with good and clear examples.[/font]

Title: histogram
Post by: on August 13, 2004, 08:29:48 am

[font color=\'#000000\']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[/font]