[argyllcms] Re: Using an i1 to measure FWA content?

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 03 Feb 2010 14:47:10 +1100

Ben Goren wrote:

On 2010 Feb 2, at 7:49 PM, Graeme Gill wrote:


spotread -S -i D50_0.0.sp


When I measure a particular piece of paper with just spotread, I get this:


Result is XYZ: 88.509296 91.511759 75.273499, D50 Lab: 96.620372 0.501330 
0.184133


But when I add -i D50_0.0.sp, I get this:


Result is XYZ: 87.826439 91.487282 72.041893, D50 Lab: 96.610330 -0.708287 
2.983602


Why the large discrepancy? I thought spotread used D50 by default? Is there 
more than one D50...?


The whole point is that the D50_0.0.sp is that it's D50 with all the UV taken 
out,
which means that it's not actually D50.
Even with samples with no FWA, this change in the illuminant spectrum affects
the readings. You could try D50_0.1.sp and the discrepancy may be less.
(Note that D50_1.0.sp is normal D50).
You would see similar things if you compared readings of instruments that are/aren't fitted with UV filters. 

Graeme Gill.

Other related posts:

  1. Home
  2. argyllcms
  3. Archive
  4. 02-2010