Digital BW, The Print

Humm...Jacob, could you please translate all this for the non-mathematical capable like me (I'm a doctor...) into some "so it means that..." form ?!
(8-)


--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Jacob" <flashinet@...> wrote:
>
> Paul, here are the numbers:
> 
>                           Std. Deviation
> 
> 0%BO:100EB6 - 0.12       10.40
> 20%BO:80%EB6 - 0.18      12.45 
> 40%BO:60%EB6 - 0.27      14.20 
> 60%BO:40%EB6 - 0.3       14.89
> 80%BO:20%EB6 - 0.49      17.29
> 100%BO:0%EB6 - 0.54      17.85
> 
> The numbers are correlated but my numbers show 4 times difference between BO and EB6, std dev show less then 2 times difference, to my eye 4 times looks like more correct number.
> 
> To make it crystal clear what is correct I've created an empty square image in Photoshop with gray background RGB 209, then selected 2 squares, 1/8 of full square each. Filled them with Black color RGB 38.
> 
> Now with analysis menu measurement I've got following:
> 
>   black area size  1.42  RGB 38
>   gray area size    4.25  RGB 209
> 
> Smoothness: (1.42 * 38)/(4.25 * 209) = 0.0607
> 
> Std dev shows: 74.18
> 
> Then I've converted 2 squares 1/8 of the big square each into black ones. So now I have a half of square black, a half is gray.
> 
>   black area size  2.85  RGB 38
>   gray area size    2.83  RGB 209
> 
> Smoothness: (2.85 * 38)/(2.83 * 209) = 0.183
> 
> std. dev shows: 85
> 
> So calculated smoothness increased 3 times which is about right, standard dev increased 10% which is not even close.
> 
> So you can't trust standard. dev, it makes inks looks too smooth relatively. 
> 
> I'm not sure what the right term should be for "smoothness", the best I can come up with is "relative specularity".
> 
> Jacob Mann
> http://www.photo3dart.com
>