Help with purple overexposed highlights

[murinae]

Hello people,

New to this forum and to ML. I'm actually a producer/editor but I have just done a project with a cameraman using the 5Dm3+ML.
Here's the question: ML apparently has a function that shows overexposed highlights in purple. I thought this appeared only as an overlay on the camera display but when reviewing I saw that it was on the footage as well (mainly concerns the overcast sky, which is now purple instead of white)

heres a screencap:



Is there an easy way to remove this? Easy as in outside the NLE?

I'm using Premiere CC to edit, so I might be able to remove it there. It just seemed that this function is very weird and impractical and I'm overlooking something obvious. Thanks for helping.

m

[Andy600]

Did you shoot ETTR? You should be able to fix it by changing the white level meta to something lower. Can you send me a DNG and I'll take a look?

[murinae]

Hey, as I said I didn't shoot this so I don't know about ETTR.
Not sure how to get a DNG of the video file either. I could upload a sample video file itself to my dropbox and share that, would this work?
Let me just check if I can fix this via changing white levels in Premiere before I bother you more

EDIT: If I change the white to gray it works, although I reckon colour correction and balance will be quite a challenge in the end. I think I can sort the rest out myself but I you still want to take a look at a file you can download a clip here:
https://www.dropbox.com/s/8vy3ciayfpzp3ux/BJ5A1981.MOV?dl=0

Any tips on how to avoid that in the future? Which feature of ML is causing this? Is this WAD or a bug?

[Andy600]

@murinae - was this shot with in-camera h.264 or is it transcoded from raw (.raw or .mlv)? I've never seen this happen with in-camera H.264 

If it's shot raw you need to get hold of the original raw files or the .DNG images so the metadata can be tweaked.

If it is in-camera H.264 it's very odd - shouldn't happen! The best way to fix this (as the image cannot be properly linearized) is to use the Video Limiter plugin in Premier. Another user has a similar but unrelated issue (but with raw files) see:http://www.magiclantern.fm/forum/index.php?topic=15231.msg148545;topicseen#msg148545. The limiter should help but it probably won't be very good.

[murinae]

I *think* it was shot in in-cam h.264, as I'm sure no transcoding happened. I got this footage straight from the cameraman's cf cards. Also you can check the sample video I posted in my post above this one.

[Andy600]

In-camera h.264 shouldn't be affected by ML. It could be a faulty PictureStyle (but I doubt it). If ML is somehow affecting the levels before encoding it's a problem - on a positive note it could potentially be very useful to understand why it's happening but my gut feeling is that this is a transcode.

[murinae]

Thanks for the link to the limiter tutorial, that seems a decent enough workaround. As to why it happened I am as clueless as you. As I said I got the footage straight from the cameraman's cards, so I don't think there was any transcoding.

This is for a low-budget doc project, so the loss in quality isn't ideal, but better than not using the footage.

So no idea how to avoid this in the future?

[Andy600]

Disable ML features and shoot a test before your actual shoot. If it plays back without the problem you are 'probably' safe. I haven't a clue why this has happened TBH. If it's not from raw then it's a bug.

[Audionut]

Looks like to much gain reduction with ML digital ISO.  Movie menu > Image Fine-Tuning.