[Leica] Re: M8 fixes

[lrzeitlin at optonline.net (Lawrence Zeitlin)]

On May 8, 2007, at 12:12 PM, Len wrote:

> Originally when Leica announced the 6 bit coding it was to identify
> the lens and optimize it's performance. Probably to correct for
> vignetting.
>
> Then it was discovered that the Leica image sensor had a reduced
> infra red filter which caused certain dark materials like polyester
> cloth, leather and even natural colors of flowers to turn toward a
> strong magenta color.
>
> In order to eliminate the magenta caused by the strong IR, Leica
> suggested using a special IR/UV filter to remove the IR and correct
> the off color cast. This is fine but the filter causes the edges and
> the corners of the photo to turn a cyan color. This problem is
> increased as the angle of the light increases through the filter. The
> widest angle lenses are the worst and the condition improves as the
> angle decreases in the lesser angled lenses.
>
> Leica found they could correct for this cyan color cast by
> compensating the color of the affected edges of the photo. Since the
> amount of compensation is different for the different lenses, the
> camera has to know what lens is being used when the special filter is
> installed. The way to do this is to code the lenses.


Leica's efforts are reminiscent of The Peterkin Papers. For all you  
non-English majors:

The Peterkin Papers is a book-length collection of humorous stories  
by Lucretia Peabody Hale, and is her best-known work.

The Peterkins (i.e.Leica) were a lovable but comically inept family  
that possesses ingenuity, logic, resourcefulness, and energy?but not  
common sense. The general formula is that the family tries to solve  
some problem in an appealingly roundabout way, fails, and is  
eventually rescued by "the wise old lady from Philadelphia," who  
always cuts the Gordian knot with some effective but prosaic  
solution. The charm of the story is not in the plot, but in the  
telling, with the building up of layers of complication, and the  
affectionate fun poked at the not-quite-cartoonish characters. The  
"wise old lady's" solution is usually obvious to the reader, or even  
the young listener, from the start.

The very first story exemplifies the formula. Mrs. Peterkin  
accidentally puts salt in her coffee. In an effort to solve the  
problem, the whole family first visits the chemist, who tries to  
counteract the salt: "First he put in a little chlorate of potassium,  
and the family tried it all round, but it tasted no better." He adds  
bichlorate of magnesia and tartaric acid:

"I have it!" exclaimed the chemist,?"a little ammonia is just the  
thing." No, it wasn't the thing at all.
They then visit "the herb-woman" who tries a long list of herbs  
including flagroot, snakeroot, spruce gum, oppermint and sappermint,  
all to no avail. In desperation they visit the wise old lady from  
Philadelphia who says "Why doesn't your mother make a fresh cup of  
coffee?" They all shout with joy, "Why didn't we think of that?"


Larry Z