Re: A "slanted edge" analysis program

Bart van der Wolf wrote: 

"Lorenzo J. Lucchini" <ljlbox@xxxxxxxxxx> wrote in message
news:aVw_e.1452$133.727@xxxxxxxxxxxxxxxxxxxxxxxx

[snip]
> 
There are many different opinions on what the mix should be.
If you want to exactly match Imatest, you could use
Y=0.3*R+0.59*G+0.11*B
(http://www.imatest.com/docs/sfr_instructions2.html almost
halfway down the page under Channel).

Other researchers use  L=0.299R+0.587G+0.114B .
And Luminance weighting according to ITU-R BT.709 is:
Y=0.2125*R+0.7154*G+0.0721*B
which comes close(r) to:
<http://hyperphysics.phy-astr.gsu.edu/hbase/vision/efficacy.html#c1>

Whatever the choice (ultimately user selectable would be best for
flexibility, but makes comparisons more hazardous), I think Human
perception should carry some weight when the goal is to optimize
sharpening.

I think I'll go for user selectable, with a default that's recommended for comparing others' results.

But all this made me wonder about something else: would it make any sense to compare the edge *position* of each (red, green and blue) channel with the edge position in the luminance channel?

I mean. SFRWin gives "red", "blue" and "green" color offsets (for measuring "color fringing"), but the "green" offset is always zero, as the other two channels are compared to green.

Would comparing the three channels to luminance, instead, have any advantage over SFRWin's approach? I don't remember what Imatest does here.


by LjL
ljlbox@xxxxxxxxxx
.

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