Blackmagic Forum

Hi there,

Many people are experience a weird pink/purple fringing problem while grading CinemaDNG's produced from the Magic Lantern raw hack on a 5D Mark III.

This appears to be a problem with the debayering algorithm in Resolve because the problem does not show up when grading the DNG's with Adobe Camera Raw (Lightroom, Photoshop, After Effects).

Here's a good example of the problem:
Resolve:


Lightroom:



Is this a known issue, and will it be fixed in future versions of Resolve? I would really like to grade my 5D mk. III footage in Resolve, but this issue alone is almost forcing me to grade in ACR instead.

Thanks!

Anyone have any info on this?

There's no automatic chromatic aberration fixing in Resolve like in Adobe apps etc. You will see the same problem with some BMCC raw files etc. That's why as shown in the link you posted, people have discovered doing noise reduction to chroma only can help. Resolve 10 will allow a better fix for this by scaling individual channels etc, but again it wont be automatic. If you want automatic fixes, Adobe might be the better solution.

CaptainHook wrote:There's no automatic chromatic aberration fixing in Resolve like in Adobe apps etc. You will see the same problem with some BMCC raw files etc. That's why as shown in the link you posted, people have discovered doing noise reduction to chroma only can help. Resolve 10 will allow a better fix for this by scaling individual channels etc, but again it wont be automatic. If you want automatic fixes, Adobe might be the better solution.

It's definitely not chromatic abberation though. It's more like random single-pixel colored noise in high-contrast areas. It's a digital artifact and looks like some sort of problem in Resolve's debayering...

there are threads talking about OS/videocards and software incompatibility, check that.

might be this?

http://forum.blackmagicdesign.com/viewtopic.php?f=3&t=9274&hilit=purple

Actually, now that I look at my footage closer, it does look like that:



It's most noticeable around the leaves of the trees and against the sky, but if you look closely at 100% there's magenta/green fringing everywhere!

I still don't think this is chromatic aberration. We were filming with L series glass (the 24-70 mk II to be precise) and the chromatic aberration in photos with that lens is nowhere near this bad! You'll also notice that it occurs even at the center of the frame.

I don't think it's OS/videocard incompatibility either, I'm using Resolve on Windows 8 with a GTX 680, but this problem also shows up on my 15" Retina MacBook Pro.

I guess I'll just have to grade in Lightroom, even though that's sort of a pain in the ass.

Here's the same frame graded to match in Lightroom:



Tab back and forth between this image and the image posted above and you will see the gigantic difference. I really, really want to grade in Resolve, but with image quality differences like this I just can't.

Erik Swan wrote:We were filming with L series glass (the 24-70 mk II to be precise) and the chromatic aberration in photos with that lens is nowhere near this bad!

How are you judging the CA in stills though? All the major RAW still convertors automatically reduce CA. I have Canon L Primes too and if i remove the CA reduction in stills (shot with 5D3) using Lightroom or Capture One, i can see the same fringing shown here.

p.s can you upload that frame in DNG ?

CaptainHook wrote:

Erik Swan wrote:We were filming with L series glass (the 24-70 mk II to be precise) and the chromatic aberration in photos with that lens is nowhere near this bad!

How are you judging the CA in stills though? All the major RAW still convertors automatically reduce CA. I have Canon L Primes too and if i remove the CA reduction in stills (shot with 5D3) using Lightroom or Capture One, i can see the same fringing shown here.

This is true, I guess, but I didn't know that ACR/Lightroom applies CA reduction at the debayering level in addition to the option to turn it on in ACR.

In other words, Lightroom has a specific checkbox to turn on "Reduce Chromatic Aberration" under the Lens Corrections panel - even with that off, I still don't have any fringing.

Here's the DNG:

https://dl.dropboxusercontent.com/u/213 ... _00000.dng

You'll notice that it's compressed vertically - this is because this is a frame from a slow-mo shot, and currently Magic Lantern compresses the image vertically when shooting 60p RAW. Scale the image by 1.61x vertically to get the correct aspect ratio.

Thanks for your help!

I think that lightroom is extra processing the image respect Resolve...

however...

Magic Lantern raw hack on a 5D Mark III

What is this? and How it works?

waltervolpatto wrote:I think that lightroom is extra processing the image respect Resolve...

however...

Magic Lantern raw hack on a 5D Mark III

What is this? and How it works?

Magic Lantern released a version of their firmware for the 5DmkIII in May that enables continuous 1080p, 14-bit RAW recording. More here:

http://www.eoshd.com/content/10324/big- ... d-mark-iii

As far as my belief goes the breakthrough involved a deeper understanding of the camera’s EDMAC (External DMA controller) and taking clean crops of the image buffer. Unlike in the burst mode, raw data is not converted to DNG format in-camera, you have to transcode it to DNG in post. This is good because you can do a very high quality debayer of the image on a powerful PC. To my eye the image looks better than with the previous nightly builds via DNG burst mode.

How do you do this passage? Your "aberration" seems like if the debayer has not grab the right RGBG sequence... (I cannot explain more accurately than that), or it did, but the DNG has the data somehow not in the place the debayer is expecting to see it. Form the images I cannot say that is a real lens aberration issue... I saw that before but my brain is not recalling where and why...

waltervolpatto wrote:Your "aberration" seems like if the debayer has not grab the right RGBG sequence... (I cannot explain more accurately than that), or it did, but the DNG has the data somehow not in the place the debayer is expecting to see it. Form the images I cannot say that is a real lens aberration issue... I saw that before but my brain is not recalling where and why...

This is what I thought initially as well, which I mention in the original post. The weird thing is that everything looks good in Lightroom, so it must be an error in DaVinci's debayering algorithm.

The other possibility is that it is chromatic aberration as CaptainHook speculated. However, that would mean that Adobe Camera Raw is doing an amazing job cleaning up the aberration in the debayering stage, and I haven't seen any similar "aberration" problems on any BMCC footage graded in Resolve.

Erik Swan wrote:

waltervolpatto wrote:Your "aberration" seems like if the debayer has not grab the right RGBG sequence... (I cannot explain more accurately than that), or it did, but the DNG has the data somehow not in the place the debayer is expecting to see it. Form the images I cannot say that is a real lens aberration issue... I saw that before but my brain is not recalling where and why...

This is what I thought initially as well, which I mention in the original post. The weird thing is that everything looks good in Lightroom, so it must be an error in DaVinci's debayering algorithm.

The other possibility is that it is chromatic aberration as CaptainHook speculated. However, that would mean that Adobe Camera Raw is doing an amazing job cleaning up the aberration in the debayering stage, and I haven't seen any similar "aberration" problems on any BMCC footage graded in Resolve.

I looked at the images, that does not look like "lens aberration", they are not "symmetrical"

RED cameras had this same issue for a long time, and apparently it was a combination of uv pollution and overexposure. Graeme made some changes to the compression and we all started using hot filters.

This is not limited to D-Cinema cameras:http://en.wikipedia.org/wiki/Purple_fringing

joemgill wrote:RED cameras had this same issue for a long time, and apparently it was a combination of uv pollution and overexposure. Graeme made some changes to the compression and we all started using hot filters.

This is not limited to D-Cinema cameras:http://en.wikipedia.org/wiki/Purple_fringing

Ok, this is interesting, however does not explain:
1) lightroom can completely get rid of it.
2) this "fringing" appear in non contrast areas as well (not an effect or overexposure)
3) in the leafs there is a lot of green/cyan fringing as well
4) if you zoom in where the white house roof meet the tree, there is a ton of green spill/compression... Is it the same phenomenon or there is a LOT of compression in the image?

I would like to see an Uncompress image of it (just a portion, not all)



(fundraising for a cause: http://forum.blackmagicdesign.com/viewtopic.php?f=14&t=12017)

waltervolpatto wrote:I would like to see an Uncompress image of it (just a portion, not all)

I linked to the original raw DNG up above. The still from DaVinci was exported out of DaVinci as a losslessly compressed PNG, so image compression is definitely not causing the problem.

I see, png is still 8bit right? can you do a portion as tiff?

However, this does not seems the magenta issue mentioned above...

EDIT: see if this can help (if you can reproduce it in resolve)

http://www.great-landscape-photography.com/using-photoshop/photoshop-remove-purple-fringing/

waltervolpatto wrote:I see, png is still 8bit right? can you do a portion as tiff?

However, this does not seems the magenta issue mentioned above...

EDIT: see if this can help (if you can reproduce it in resolve)

http://www.great-landscape-photography.com/using-photoshop/photoshop-remove-purple-fringing/

Here is the TIF:

https://dl.dropboxusercontent.com/u/213 ... _1.4.1.tif

I've tried a couple methods to get rid of the pink fringing in Resolve, and they help somewhat, but it is never removed completely and I can never get anything close to the Lightroom result in terms of sharpness and lack of color noise.

If anyone wants to give it a shot in Resolve using the DNG posted above, I would be grateful!

Here's a zoomed in view of the near dead-center of the frame in question, you can clearly see the fringing/aberration in effect even at the center (which should rule out lateral CA from the lens) and a weird digital pattern that makes me suspect this is due to an error in the debayering.



Can anyone from Blackmagic Design comment on this? It clearly looks like an error in the software here...

The "blockiness" is what I do not get it, as if the debayer method is wrong....

BC, care to comment?