From: michael.uplawski@uplawski.eu   
      
   Wei Lu wrote in sci.optics:   
      
   >Yes, like bob posted, what you need is a spectrometer designed for   
   >surface reflectance measurement (380~780nm). I am not familiar with the   
   >products in the market, yet I think it could use an integration sphere   
   >with an opening size to cover a meaningful area, but not too big to   
   >deviate much from the measurement principle, maybe 5~10mm diameter, and   
   >with a space that could hold an apple under the opening.   
      
   Thanks for going into further detail.   
   I really like that my idea is not completely dumb and that there   
   *are* technical solutions.   
      
   A problem will be the price of the tool. I will have to purchase it   
   privately (then use it for my pleasure).   
      
   >Then you need the software to calculate the colour of the surface.Some   
   >device may have the feature,   
      
   What I saw on the Web came with the software. Second problem: I am   
   glued to Linux. Similar programs that I have used, ran in the Wine   
   (Windows-) emulator, but I would have to assure that this is   
   possible with the new tool.   
      
   >or you can DIY (in principle, by multiply   
   >the incident spectrum (sun's spectrum AM1.5 could be a reference), the   
   >measured reflectance spectrum, and the 3 response curve of the human   
   >eye,and integrate across 380~780nm). You will get a color coordinate,   
   >which are 3 quantitative value that can be used to compare, reproduce,   
   >or automatic select by machine.   
      
   While I comprehend everything that mentions a “reference” .., once I   
   want to really apply your advice, I might have to come back here and   
   ask a few more questions… though you have probably already   
   answered each one.   
      
   >It should be noted that the result is the colour and brightness   
   >perceived by a "standard" observer (the integration sphere), not the   
   >same as human eyes perceived in normal conditions. So you should not   
   >select an area of the "preferred" colour (in this case green) directly   
   >from the colour space (as in   
   >https://en.wikipedia.org/wiki/File:CIE1931xy_CIERGB.svg), instead, like   
   >in machine learning, you should use the "preferred" apples as samples to   
   >get a "preferred" colour space area, then use it as the selection standard.   
      
   Yes. Believe it or not, that is what I do already: I take a standard   
   apple (“big enough”, about 110g and just about as red/yellow as is needed)   
   and   
   compare in case of doubt.   
      
   ) These are cool followups to my initial post. I have assumed that   
   I will be slightly swamped but it could be worse.   
      
   Cheerio, have a nice week-end, marry X-mas or whatever it is, you   
   will have these days.   
      
   Micheal   
   --   
   “When you feel there is an unfair burdon on your shoulders   
   well – that's just the way it is sometimes” (Winston Groom/Forest Gump)   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)