[popo]

[quote name='Brightcolours' timestamp='1291476531' post='4757']

I have no idea why you wonder why PF is LoCA. It looks different, the colour usually is different, and where LoCA shows magenta and green, PF always is on its own in one colour (from blue/violet to red-ish).

[/quote]



Turning that around, why is there a need for a different mechanism when LoCA seems to me adequate to describe both. I haven't seen anything yet that suggests it isn't.





Full test output





Crop from bottom of top-middle.





Crop from top of bottom-middle.



Anyway, here's the result of my test. I created a test image with relative levels of 0% background, 25% for lower star backgrounds, and 100% for upper star backgrounds. Put the EF 85mm f/1.8 on the 450D, and manually focused on the vertical point of the middle stars at f/1.8. The lower contrast stars at the bottom show the expected regular LoCA colours, red/magenta-ish in front of the focal plane, and green-ish behind. Looking at the top 3 there's a lot of magenta "PF" on and in front for the focal plane. It's more interesting behind the focal plane, with a tiny amount of blue before going green mixing into yellow. The green/yellow thing seems dependant on the direction of contrast change with defocus.



This was obtained with one lens in one shot. It shows LoCA and PF happening, the only difference between them is the lightness of the region.



I'm open to discussion if there may be anything I've overlooked or misinterpreted here. Different lenses may exhibit different colours so could have the same test performed to see if that remains the case. I can repeat this for my other lenses on request.