Purple fringe problems on Leica M9

[SJP]

Originally Posted by jaapv

I just want to show from time to time that I dislike and disable spell checkers

Interestingly I was referring to the whole contraption displayed & not to the spelling

@Rip, no offense intended (in fact the opposite) but you are a weird member of this weird community. Marriage of camera, "formula one" & home cooking. To put things in perspective I spent about ½ an hour last weekend sawing some (hard) wood into shape to make a fake "stage knife" handle for my wife. She has to kill someone on stage without running a serious risk of succeeding The "blade" is made of cardboard from an old shoe box with aluminium tape & the whole thing actually looks more convincing than the original. My members of staff must not find out about this - as it would permanently damage my street credibility (if any).

[bpalme]

When light goes in a lens it doesn't come out in a nice neat pattern the way it went in. Especially blues and purples they get scattered a little and need another lens to try to correct it. If you take a picture of something bright like a piece of chrome it may have purple fringing around it called chromatic aberration.
Google Images In the telescope world of refractors you will see a blue ring around something bright like the moon in cheaper telescopes(achromatic). To correct this there are extra lenses to correct it called apochromatic. There are some with two extra lenses to correct it(doublets) and it won't correct it all... so there are more expensive ones that ad even another lens (triplets) to get the purple fringing down even more.