06-15-2011, 11:58 AM
The purple would occur in a not focussed area, and here the purple is VERY extreme in the IN focus area. Also, we don't see a purple edge, but purple bleeding into the dark area from the very bright area.
LoCa will occur just because of being OOF. This kind of PF occurs ONLY with a lot of light. While to the casual viewer it may look all the same (purple artifacts), the phenomenons are just very different.
PF is being combatted by different lens coatings (specifically the back element), which for instance Sigma introduced with the DG and DC series, and Tamron when they started to introduce Di and Di II lenses.
As far as I know LoCA can only be prevented by making the lens design really apochromatic.
LoCa will occur just because of being OOF. This kind of PF occurs ONLY with a lot of light. While to the casual viewer it may look all the same (purple artifacts), the phenomenons are just very different.
PF is being combatted by different lens coatings (specifically the back element), which for instance Sigma introduced with the DG and DC series, and Tamron when they started to introduce Di and Di II lenses.
As far as I know LoCA can only be prevented by making the lens design really apochromatic.