12-04-2010, 04:28 PM
(This post was last modified: 12-04-2010, 04:34 PM by Brightcolours.)
[quote name='popo' timestamp='1291478894' post='4758']
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.
![[Image: IMG_4061.JPG]](https://lh3.ggpht.com/_UXW65nXXeP4/TPpgPK3cTAI/AAAAAAAAFW0/EptFc7xzFUo/s800/IMG_4061.JPG)
Full test output
![[Image: topcrop.jpg]](https://lh5.ggpht.com/_UXW65nXXeP4/TPpl430zk8I/AAAAAAAAFXI/IUsk-Ezb-F0/s800/topcrop.jpg)
Crop from bottom of top-middle.
![[Image: lowcrop.jpg]](https://lh3.ggpht.com/_UXW65nXXeP4/TPpl54uxezI/AAAAAAAAFXY/MbfQ581jOKo/s800/lowcrop.jpg)
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.
[/quote]
No, it does not show PF and LoCA happening. It only shows LoCA happening (magenta blur to the front, green blur to the back).
All lenses that show LoCA (most wider aperture lenses and macro lenses) have exactly the same thing: Green blur on one side of the focal plane, purple on the other side.
Check photozone's more current reviews to verify that.
PF only is one colour, and only around very bright areas. It also usually only radiates to one side of bright "holes", where LoCA is in the whole blur/bokeh.
BTW: The PF examples I have... the top one, from the Sony 16mm f2.8 fisheye, does not seem to be PF now that I looked at it again. It seems to be NORMAL (La) CA, with green edges going from the "dark" into the bright, and purple edges going from the bright into the dark. It was a corner crop, so I am pretty sure that is normal CA and not PF (and certainly not LoCA).
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.
[/quote]
No, it does not show PF and LoCA happening. It only shows LoCA happening (magenta blur to the front, green blur to the back).
All lenses that show LoCA (most wider aperture lenses and macro lenses) have exactly the same thing: Green blur on one side of the focal plane, purple on the other side.
Check photozone's more current reviews to verify that.
PF only is one colour, and only around very bright areas. It also usually only radiates to one side of bright "holes", where LoCA is in the whole blur/bokeh.
BTW: The PF examples I have... the top one, from the Sony 16mm f2.8 fisheye, does not seem to be PF now that I looked at it again. It seems to be NORMAL (La) CA, with green edges going from the "dark" into the bright, and purple edges going from the bright into the dark. It was a corner crop, so I am pretty sure that is normal CA and not PF (and certainly not LoCA).