Exposure correction + Haze Removal results in wrong colours in dark images

[rebio]

Short description Combining strong exposure correction and haze removal tool results in a strong colour shift in dark images

Steps to reproduce

1. Open an underexposed image (mine was a darkish room with a bright window. The camera adjusted itself to the bright window and not the dark interiour)
2. Increase the exposure correction (like +2-3 EV)
3. Haze Removal tool
4. Look at dark areas

Observed behavior RT shifts the colour of dark areas

1. Default view in RT

2. +EV correction

3. +Haze Removal

Expected behavior RT does not shift the colours

Additional information Since I use the haze removal for something it was (I guess) not designed to do I expect the error to be on my end here. Yet this behaviour will may also show up in a regular usecase.

Same results on my Windows and Linux machine.

Same results across different dev versions of RT

[chaimav]

Haze removal is known to introduce a blue color cast under some conditions. Per Rawpedia "Might remove color casts, but might also introduce a blue cast which can be corrected using other tools." Slide the saturation slider to left to remove the color element of dehaze.

[Benitoite]

It looks clipped on the low end... please post your RAW file per the instructions.

• Exact Version of RT
• Name and Version of OS
• RAW Image file and PP3 sidecar

[gaaned92]

As haze removal is a tool dedicated to fight the atmospheric haze, it is a surprising idea to try it on a tissue photo and after complain that it doesn't work! But perhaps it is a valid use case.

[rebio]

Haze removal is known to introduce a blue color cast under some conditions.

@chaimav If the tool can "introduce a blue cast" I wouldn't expect that it changes the very dark blues so much. I would rather expect a blue 'fog' over the entire image or the areas where the fog was present which could be changed using eg. the Color Toning tool.

It looks clipped on the low end... please post your RAW file per the instructions.

• Exact Version of RT
• Name and Version of OS
• RAW Image file and PP3 sidecar

@Benitoite I can not post this RAW file here since it's an image taken at a wedding. I hope you understand why I will note share this photograph on the internet. It should be rather simple to reproduce though. I just need a dark room, a bright window and something coloured dark blue. Once I have it I will share the image.

As haze removal is a tool dedicated to fight the atmospheric haze, it is a surprising idea to try it on a tissue photo and after complain that it doesn't work! But perhaps it is a valid use case.

@gaaned92 Where do I "complain that it doesn't work". I opened this bug report since it could be one. If the devs think that it's not a bug they will close the report.

[Benitoite]

@rebio No one has been convinced this is a bug. Haze removal (Dark Channel Prior) works well for haze removal in properly exposed images.

[Beep6581]

No raw file provided and tool not used as intended so closing.