Color in neutral highlights after raw conversion

[davros]

I've just replaced my Canon 350D with a 60D. When I do raw conversions using PWP get strong colors in the neutral highlights in a small number of photos . It seems to occur close to or at the camera clipping level where a significant number of pixels are clipped in the camera. Typically the neutral appears to be green deficient. I don't recall ever having seen this happen with the old camera.

It doesn't happen when I do raw conversion with the Canon supplied software, but I also notice that the Canon software appears to lose a lot of highlight detail that PWP produces (even without using highlight recovery) due to clipping. If I clip in the RGB space after raw conversion in PWP I can eliminate the false color, but this loses a lot of the highlight detail that PWP normally provides. It also disappears if I use HSL color space in the raw conversion. although this is not generally optimal for the result as a whole.

The issue is apparent in both PWP5.0 and PWP6.0. I'm not sure at this stage whether its some artefact of the conversion process, the result of inappropriate parameter settings, or a problem with the camera.

Has anyone else had this problem, or any suggestions for anything to try to resolve it ?

[ksinkel]

The highlight recovery function in the raw converter tries to restore missing highlight information by analyzing the non-blown channels and inferring the information from the 'blown' channel. This is essentially a guessing game. In some images the reconstructed information may be underestimating the green information and thus exhibits a magenta cast. This is still useful, because additional detail has been recovered. Usually you can eliminate the magenta cast by running the image through the Color/Correction transformation after completing raw processing. In the Correction transformation, select the cast color and set it to neutral.

Kiril

[den]

To supplement Kirl's suggestion, I sometimes will use the Paint Tool in 'HSV-H only' mode and Probe a color near where the image area starts to turn Magenta... ...the following illustration is a crop from a Canon 350D CR2 PWP6 conversion [HSV mode] with a Level 4 Hilite Recovery:

IMG_8547_crop_magenta_hilites_corrected.jpg (34.44 KiB) Viewed 5590 times

...then perhaps make a Color Temperature change to 'warm' the image highlights if too 'cool'.

[davros]

Thanks for these suggestions. They both appear to be useful.

I understand how using highlight recovery can lead to this sort of problem. However in the examples I have seen the effect occurs even with highlight recovery set to "None". As an example here is a crop from an image process with highlight recovery set to "None".

211F012.jpg (12.42 KiB) Viewed 5464 times

[den]

(1) Was the 60D's Highlight Tone Priority option (Custom Function II.3) 'on' to capture the above posted image? If so, at what ISO setting? I understand that by using the HTP at an ISO200 or above will provide about one stop more highlight headroom perhaps reducing highlight RGB channel clipping...

(2) Is the camera's histogram Luminance? Can it be set to show RGB channels?... ...which may be more helpful than Luminosity when 'Exposing to the Right?

(3) Is it possible to make availabe the RAW file?

(4) Perhaps another PWP RAW conversion approach could be... ...(A) create a preference PWP HSV conversion image version and if the magenta appears... ...(B) create a second PWP HSL conversion with preference highlights... ...then (C) Composite-Blend the two conversions with a Highlight tone range mask where the preference HSL highlights are blended with the preference HSV upper-middle-lower midtones and shadows.

[den]

Hmmmm... (1) above may only apply to in-cramera processed jpegs and does not effect the recorded raw data. Anyway I found where I read this: http://www.dpreview.com/reviews/canoneos60D/13

...but do I correctly understand that exposure metering mode does? ...Evaluative metering (linked to all AF points); Partial (6.5% at center); Spot metering (approx. 2.8% at center); and Center-weighted average...

If so, then anything other than Evaluative would tend to over expose highlights and under expose shadows if not center framed.

Incidently, the request for a RAW file is to explore PWP6 conversion options, 'dcraw' conversion, and DPP conversion.

By the way, I envy your choice of upgrade!!!!!

[davros]

Den,

I've been away for a few days and just caught up with your suggestions. Highlight tone priority was off when this picture was shot. Anyway as you say I'm not actually sure whether highlight tone priority effects raw image data.

I tried blending HSV and HSL raw conversions as you suggested and it works quite well, at least on this image. In this case a suitable mask based on selecting highlight areas with low saturation required only minimal touch up to get a good result.

I've also tried raw conversion using ufraw, and it produces similar results on this shot to PWP HSV conversion.

I had problems trying to attach the file to this message. It seems the forum doesn't like .CR2 attachments, or perhaps the file is too large, but you can download the raw file from http://terry.taralga.com/files.

[den]

Thank you 'davros'... ...the 211F012.CR2 file is downloaded. Noticed that it has your DPP adjustment settings embedded. Initially, when returned to DPP defaults; using 'dcraw'-linear conversion; and using a PWP6 HSV default Raw Dialog... ...all will show R,G,B channel highlight clipping and magenta... ...and it appears that the highlights are over-exposed 0.67 to 1.00 ev... ...will do some more trials and advise but for the moment, LIFE intrudes upon hobby time!!! ...more later...den...

[den]

The attached PWP6 RawDialog wfl file yielded the following result where the conversion was done in the HSV color space and sRGB colors:

211F012_pwp6conv_den-wfl.jpg (38.97 KiB) Viewed 5115 times

Subsequent workflow steps needed are (1) Chromatic Aberration [R=-0.082; B=-0.0410]; (2) ChromaReduction with a Blur radius=3 as suggested here: http://www.dl-c.com/board/viewtopic.php?f=4&t=423#p2747; (3) final tone; (4) vibrance-saturation colors; and (5) sharpening.

A temporary download link [expires in 30 days] to the suggested PWP6 RawDialog wfl is here: http://www.ncplus.net/~birchbay/misc/davros_211F012CR2/

Kiril... would it be possible to change the message board settings to allow *.wfl extensions?

[den]

'davros'...

...also at the temporary 30 day link [http://www.ncplus.net/~birchbay/misc/davros_211F012CR2/] for download is a 211F012_DPP_den.CR2 file [16mb] with suggested DPP embedded conversion settings, if of interest. DPP version 3.11.4.10 was used.