GH4 What is this purple halo???

F

Finster

Well-known member
What do you call the purple halo that's surrounding the white in this image??? I cropped in tighter so you can see it more clearly ...

blue_01.jpg

This purple halo always appeared around bright white objects that I filmed earlier this evening, and only when I used my Canon FD or Nikon AIS lenses w/ adapter. I don't see this purple haze when I used my Panasonic 25mm or Voigtlander 17.5mm.

I was filming in 4K.
 
That's chromatic aberration. I believe I've read something about the GH4 having lens profiles for CA removal, so that may explain why it doesn't show up with the Panny 25mm.
 
Can a sensor itself cause CA? I have a Nikon 35mm which always produces it wide open, but my Zeiss line up & Nikon 24-120mm f/4 don't (using them with Scarlet, all 3 Blackmagic cams, & 5D Mk3).

I hope not because I plan on using a GH4 with a Speedbooster.
 
Purple fringing is a little tricky, because it doesn't quite fit how CA usually works. I just use the term PF for cases like these.

I do believe it's an interaction with the microlenses and the lens itself that causes this. Newer designs take into account digital sensors, which is why the Voigtlander, although not a Panasonic lens, does not show this problem.

It's also why I don't like using older lenses for digital photography: The greater resolution that is demanded for photos means that old lenses show up their design issues very easily.
 
It's bad when I have the apurature wide open on my Canon FD f1.2 & Nikon AIS f1.4 lenses. I thought it was only when the whites were slightly blown out, but if I set my Canon FD to f2 and up the ISO so that the whites are still slightly blown out, I don't see the purple fringing.

And the Nikon AIS seems worse than the Canon FD.

This is all based on extremely non-scientific tests here in my hotel room. Just walking around my room filming white objects.
 
You'll want to stop down from fully open on older lenses, if the CA is objectionable. It can also be considered a kind of aesthetic flair, if you like it
 
KINOKS said:
Canon FD and Nikon AIS are old lenses, and controlling stuff like CA has improved greatly over the years on the lenses and also on the cameras them self when combined with the right glass duo to special programming in the software.
Click to expand...
The flickr link was to the older non AF version SMC Pentax-A* 200mm F4 Macro ED that first came out in 1984 instead of the newer AF version FA* 200/4 Macro ED [IF] that came out in 2000.
http://www.pentaxforums.com/lensreviews/SMC-Pentax-A-Star-200mm-F4-Macro-Lens.html
http://www.pentaxforums.com/lensreviews/SMC-Pentax-FA-Star-200mm-F4-Macro-Lens.html
[url]http://kmp.bdimitrov.de/lenses/primes/tele/FA200f4-Macro.html
http://kmp.bdimitrov.de/lenses/primes/tele/A200f4-Macro.html
[/URL]
 
In most cases Purple Fringing is chromatic aberration that is seen when shooting wide open with older lens designs.

I sold my Nikon-mount Zeiss ZF 50mm f/1.4 lens because I could not stand the amount of purple-fringing visible in both stills and video when shooting at apertures wider than f/2.8.

Panasonic m43 bodies will correct chromatic-aberration while you shoot provided the camera has a correction profile for the lens. ( i.e. CA issues are corrected for m43 lenses )
 
Hello everyone.
There's something a bit odd related to CA.
I've seen lots of CA in shots on the GH4 taken with lenses that in other cameras did not produce that much CA. And it's not a matter of 4K resolution or sensor crop because it's visible at 1080p. And I'm talking about premium glass. I'm going to do a couple more rests but I feel something odd is going on here. Perhaps the OLPF is increasing CA? Any other ideas? Maybe the adapter is off by a micron?
 
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All this feedback has been extremely helpful. An earlier post mentioned using a UV filter. This seems to help some. Additionally, I'm not opening any wider than f2. Did a lot more filming today using my AIS & FD lenses. Footage looks great.

I don't think I'll ever be able to part with my FD lenses. I love the 85mm f1.2, even at f2!

Then again, if Metabones ever releases that EF to m43 Speed Booster! ...
 
I would vote against it being chromatic aberration, because we're not seeing any green. Typically chromatic aberration will produce a purple fringe on one side of the item and a green fringe on the other.

I would say it's more related to overexposure. Check out the wikipedia article on purple fringing, and try some of its recommendations to see if you rein in the purple.
http://en.wikipedia.org/wiki/Purple_fringing
 
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