RF 24-105 F4L horrible purple fringing

left top branch exhibits strong purple fringing

picture taken with R, raw format, converted in DPP, also tried LR and Luminar, could not remove the purple fringing in the branches.

Purple fringing happens most with blown highlights.

https://www.dpreview.com/forums/thread/4569101
and

Try applying lens correction in DPP or in camera. They should nearly eliminate this stuff. IMO, Canon has relied too heavily on the correction side and too little on the design side. It almost feels like they decided to take short cuts, but I'm sure its more complicated than that. Either way, they really have been relying on the correction to save some aspects of the lens design and optically correcting the stuff that can't be easily corrected for in body or in post. I hoped they would go away from this, but it appears that's not the case.

Like others have said, you can minimize the effect by omitting that kind of massive contrast between light and dark. Normally, it will even make you images better, as that particular transition isn't normally appealing.

phatgreatwall wrote:

left top branch exhibits strong purple fringing

picture taken with R, raw format, converted in DPP, also tried LR and Luminar, could not remove the purple fringing in the branches.

Modern software deals with this well, in particular, DXO PL4 works well on purple fringing (it could not do DeepPrime as the file was not raw).  I ran you picture through DXO PL4 and applied purple fringe removal. DXO PL4 also did some lens distortion correction (not sure if it should have, but it was enabled by default and it also did some sharpening/detail improvement).

I started with the Purple Fringing "automatic" settings and it suggested 100% and size=8, but I upped the size to 10 as it seemed to kill more of the purple. BTW, I would suggest punching up the saturation by about 20% (not done to the picture below) and the picture looked better IMO as it was a gray overcast day and the purple fringing did not come back.

DXO PL4 HQ mode with Purple Fringe = 100% and  size=10

phatgreatwall wrote:

thanks for all the info. i downloaded a trial of DXO and it works like magic. DPP/Luminar could not completely eliminate it, which is surprising since DPP is supposed to be Canon's official software that covers their lens flaws. also the fact that an L lens exhibits such bad purple fringing is a shocker, i would've thought L for the price would be at least better than my iphone.

I'm not an expert on this, but my understanding is that purple fringing is largely due to the UV light getting to the sensor (see: https://en.wikipedia.org/wiki/Purple_fringing). UV light is out of the range of wavelengths for which the lenses are designed, but which the camera ends up detecting as purple.

Even people with very high-end lenses will get purple fringe in the right conditions. It turns out the overcast days have a lot of UV light which makes the problem worse.

In the cases where purple fringing becomes seriously bad, it can be easily removed. But you may not want to process it out all the time due to the computational effort and time and the risk of damaging something else in the image.

phatgreatwall wrote:

the fact that an L lens exhibits such bad purple fringing is a shocker, i would've thought L for the price would be at least better than my iphone.

No, it's not shocking at all.

1. You just should have stopped down. I really don't see a reason to use anything wider than f/8.0 for this shot.

2. If you didn't want to stop down you should have used a prime.  A prime also allows you to shoot at a bit wider aperture than f/4.0 giving you more separation still being stopped down enough to keep the fringing very low.

3. You should have exposed for the highlights

4. A polarizer filter would have helped a little too in this case

Look, I can imagine 2, 4 and even 3 are too much hassle, no problem. But 1 is just user error. Yes, it's an L lens, but it's only 1200 euro, and most important: it's just a zoom, and therefor it should be treated just like that.

There are some primes with (close to) zero fringing wide open, but at the 24mm focal length even expensive primes need to be stopped down a little to avoid fringing.

This is by far Canons worst RF L lens (based on the one I have, but its approximately 1/2 the cost of most other RF L lenses and suffer also most as much as the RF 600/800 non-L lenses, uncorrected, from such distortions). I think the older EF 24-135 has better performance out of the box.

Whilst you can correct it with careful exposure control or post processing the raw images, without these correction, suffer highly from several distortions - I have it but stopped using it after I purchased the L trio (RF 15-35 L, 24-70 L. & 70-200 L) which suffer much less from such . Mine pocket now suffers instead (their all at least twice the price of the 24-105). The downside is their weight and 3 replacing 1 lens.