The 12-35 mm for landscape.

Started Jan 29, 2013 | Discussions thread
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gollywop OP Veteran Member • Posts: 8,070
Re: Not every lens does this!

Anders W wrote:

gollywop wrote:

Paul De Bra wrote:

The example image that was shown illustrates a problem with this lens that is not present in all lenses!

On my Canon dslr I had the Sigma 18-125 lens for about a year. This lens (which had issues like autofocus) was extremely resistant to purple fringing. I later got the Canon 17-85IS which is notorious for loads of purple fringing. I replaced it with the 17-55IS which was more resistant to PF.

I currently have the E-M5 with Olympus 12-50 and I have the Panasonic 20mm f/1.7. Under the exact same circumstances, shooting at 20mm the 12-50 will not show purple fringing where the 20mm shows very clear purple fringing.

This is not so, Paul. The 12-50 has considerable CA. I just checked a shot, for example, that I took with this lens at 18 mm, and there is decided purple fringing. Perhaps you have CA removal on by default, or perhaps you are simply not looking in the right places. The CA is readily removed in ACR. If you're shooting jpeg, I would image the camera's jpeg engine removes it as well.

"Purple fringing" is longitudinal CA, not lateral. This kind of CA is not eliminated by any MFT body and can't (AFAIK) be eliminated automatically by any RAW converter either. The checkbox labeled "remove chromatic aberration" in LR 4.x removes lateral CA only, not longitudinal. In order to get rid of the longitudinal CA, you have to manually use the defringe tool.

Yes, this is so, and the manual adjustment works well.

The 12-50 may well have quite a bit of lateral CA but based on what I have seen so far it has less longitudinal CA than the 12-35 (and most other Panasonic lenses, including the 20). A bit of PF towards the edges of the frame is a common characteristic of Panasonic lenses.

What you saw as "purple fringing" on your 12-50 may well have been lateral CA rather than longitudinal. It is sometimes hard to distinguish between the two in practice since the purple/magenta fringe caused by lateral CA is often more easily visible than the green fringe on the other side (longitudinal CA in the in-focus area yields purple fringes only, not green plus purple/magenta; in out-of-focus areas, the fringes caused by longitudinal CA are purple if the object is in front of the focus point and green if it is behind).

Again, you are no doubt correct.  I've studied the matter, but I still have troubles distinguishing what's what when I'm looking at an instance. I'm just happy that the adjustments in ACR (manual at times) seem to handle just about everything I've encountered.

Interestingly, I have had nowhere near the success in using the CA tools in Photo Ninja, which are supposed to be super duper.  They don't appear to be.  There are cases that are dealt with with ease in ACR that simply will not fall to the PN tool.

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