Magic Lantern Forum

Using Magic Lantern => Post-processing Workflow => HDR and Dual ISO Postprocessing => Topic started by: Satis on May 22, 2014, 12:34:02 AM

Title: Pink highlights
Post by: Satis on May 22, 2014, 12:34:02 AM
Hey guys,
I've been browsing around for quite a bit, because I supposed this is a classical error, although I couldn't find much.
I am well aware of the purple-highlights effect in case the ISO is amped down, but this has happened without all that thing, simple dual iso: 100 and 800.

Here are the files, the original interlaced image seems perfectly fine, but once I process it with cr2hdr the result is a nasty turn in blue/purple/pink.
The nature of this error showing up I'm rather sure it's a processing fault of the cr2hdr...

How can this be fixed?
A quick fix would be erasing all the excess info of the image, but I have no clue how to get there.

also, I'm using a rather recent version of it (v1.0.3)

(http://i.imgur.com/GeLgQYB.jpg)
Title: Re: Pink highlights
Post by: a1ex on May 22, 2014, 07:45:04 AM
Upload the CR2.

also, I'm using a rather recent version of it (v1.0.3)

Recent version of what? I did not label any of my tools as v1.0.3.
Title: Re: Pink highlights
Post by: Satis on May 22, 2014, 01:33:55 PM
Ok, the version has to be connected to the Lightroom cr2hdr plugin I downloaded yesterday.

Here is the file:
https://drive.google.com/file/d/0BzBsjJnB7tI2TEVmMEVvbkdmNlE/edit?usp=sharing

part of a raw video timelapse sequence.
Title: Re: Pink highlights
Post by: a1ex on May 22, 2014, 02:16:57 PM
Confirmed, will take a look these days.
Title: Re: Pink highlights
Post by: Satis on May 22, 2014, 02:42:38 PM
Thanks a1ex!
Title: Re: Pink highlights
Post by: Satis on June 08, 2014, 03:11:56 AM
Did you find something?
Title: Re: Pink highlights
Post by: a1ex on June 08, 2014, 07:19:25 AM
Yes, confirmed the bug, but didn't fix it yet.
Title: Re: Pink highlights
Post by: Satis on July 27, 2014, 09:11:26 PM
Hey A1ex, respect for all the work that has been put into the development. I'm not trying to get a quick fix for the problem - this scene is not all that important to me - but I'm curious of what actually causes this effect.
I suppose the dynamic range of the original raw images exceeds that of the dual-iso converter's understanding, hence results in pink clipping.
As this is something I have seen in other contexts as well - blown highlights in raw sequences with iso's lower than 100, and maybe other instances too - this is a matter of extending the converter's capabilities to handle overblown highlight info, right?
Title: Re: Pink highlights
Post by: a1ex on August 29, 2014, 06:07:34 PM
Solved.
Title: Re: Pink highlights
Post by: Satis on August 29, 2014, 11:30:29 PM
Thanks! 8) What was the problem, clipping due to overflowing data?
Title: Re: Pink highlights
Post by: a1ex on August 30, 2014, 08:08:49 AM
These highlights were at 16383 (a bit unusual, since white level is usually around 15000), which caused two overflows:
- when matching exposures, there is usually a small black level difference (around 60 in my worst-case samples)
- I also add some anti-posterization noise, which also caused a few pixels to become 16384 => overflowing to 0

Before, these very bright pixels were tagged as bad pixels, and interpolated. But here they are grouped together, so interpolation didn't work.