Re: filmscanners: IT8 Calibration was Re: filmscanners: I love/hate SilverFast

[Arthur Entlich <artistic@ampsc.com>]

Rob Geraghty wrote:
> 
> "Arthur Entlich" <artistic@ampsc.com> wrote:
> > I am very intrigued by the number of people on this list how have color
> > deficiency.  Does anyone know how common this is in the general
> > population (or even just the male population)?
> 
> I'll have to look that one up.  I *think* it's more common in men than
> women,
> but I don't remember the numbers.  Maybe the hospital library has an
> appropriate text somewhere...
>

Yes, males are much more common, and here's why  (this came up in the
other scan list just a few days ago, so please excuse my cross
posting...

> There are a number of different types of color blindness, or color
> deficiency, a preferred term. (Daltonism is the red-green variety, the
> most common type)  Each has specific (and different) organic causes,
> which are genetic in origin, and are sex-linked, in this case, the genes
> for the condition are carried on the X chromosome, making males more
> vulnerable to it, since they only have one X chromosome, and therefore
> it cannot me masked by a dominant gene if their X chromosome carries the
> color deficiency gene.  Since females have two X chromosomes, if either
> is a dominant "normal" gene for color perception the color deficiency
> gene is masked.  All color deficient males pass on that gene to their
> female offspring since it is on their X chromosome, which may or may not
> be masked depending upon if the X chromosome from the woman's side has
> the color deficiency gene or not.
> 
> A woman who manifests color deficiency herself (which means both her X
> chromosomes carry the gene) can only produce color deficient sons.  If
> she carries the gene but it is masked by a "normal" gene on her other X
> chromosome, approximately half of her sons will manifest color
> deficiency. Female offspring possibilities get more complex and depend
> upon both the male and female parents. However, no female offspring can
> manifest color deficiency unless the male in the pair has it, even if
> the female of the pair carries the color deficiency gene on one of her X
> chromosomes or actually manifests color deficiency (meaning she carries it on 
>both her X genes). 
> 
> So much for Genetics 101.


Art