Re: How to translate log density readings to percent?

From: Loris Medici ^lt;>
Date: 09/07/04-11:55:47 AM Z
Message-id: <002201c49503$ea374df0$bd02500a@Loris>

Dave, thanks for the contribution.

But how shall I see that I'm dealing with dmax if I don't map the hypothetical max density value of 95.32% to 100%?

I'm asking all this because I'm about to puchase a densitometer (which reads in log values - not percent) and want to figure out how I can use it to make the most correct adjustment curves for my digital negatives. AFAIK, I need to convert the log readings to percentages so that I can design curves in Photoshop. My approach was: the densitometers that read percent values can both set dmin (zeroing) and dmax boundaries in measurement, but the "normal" densitometers have only zeroing (no dmax preset). Therefore, I thought I should map dmax myself by means of calculation.

Thanks again,

  ----- Original Message -----
  From: Dave Soemarko
  Sent: Tuesday, September 07, 2004 7:35 PM
  Subject: Re: How to translate log density readings to percent?


  You do not need to map (Dmin, Dmax) to (0%, 100%). The values you have for R and 1-R are already in percentage.

  That is, if you subtract the real Dmin (0.12) and consider Dmin to be 0, then at density of 1.33 the reflectance is 4.68%; the opacity is 95.32%. You do not map that to 100%. That would be incorrect.

  Dave S
Received on Tue Sep 7 11:56:52 2004

This archive was generated by hypermail 2.1.8 : 10/01/04-09:17:55 AM Z CST