Re: what is the "Luther" condition?
Re: what is the "Luther" condition?
- Subject: Re: what is the "Luther" condition?
- From: email@hidden
- Date: Thu, 24 Apr 2003 12:44:31 EDT
>
Which begs the question : what is the "Luther" condition?
In this context, the Luther condition is satisfied if the camera spectral
sensitivities (camera color responses) are linearly related to the human
color responses (standard observer xyz-bar color matching functions). If
satisfied, the camera is a colorimeter and observer metamerism color errors
are minimized. As a practical matter, this is extremely difficult to
accomplish. Human color responses have 4 lobes. Camera filters for 3 RGB
channels that meet the Luther condition are easier to design than
manufacture.
>
Since most color perception (many say 90% or more) occurs in our brains,
>
better sensors are not the answer to the current problems with digital
>
imagers or color reproduction.
Perhaps, but I've measured several cameras with monochromators to determine
camera RGB responses to see just how well they satisfy the Luther condition.
Loosely speaking, the best are in the 95% range. This results in color errors
in the 10+ Delta E range. Better sensors are part of the answer, but better
does not just mean colorimetrically. Colorimetric quality and other design
goals can often be at odds with each other so the optimization is quite
complex. For instance, I'm not sure I would prefer better colorimetric
accuracy with noisier images...
Eric Walowit
Tahoe
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