This clipping should not happen and means the latitude needs to be reduced. The “hard” variant sets a zero derivative at both ends of the curve, so there is more “tension” in the spline to converge toward the min/max luminance in an asymptotic way, as opposed to no derivative condition, that produce a more sloppy curve which, in you case, is oscillating but the overshoot/undershoot get clipped by the sanity check. Namely, if you put contrast to 1, you can’t achieve a straight line in “hard” mode, there is still curvature happening at both ends, whereas “soft” allows a straight line from end to end. An in all, if you divide the latitude by 2 and try both modes, the result should be self-explanatory.
Ok, but again… is that area clipped in the first place ? Does it need reconstruction at all ? Because you can set the highlights threshold and exclude it from reconstruction if it is good. Or perhaps send me the RAW one way or another.
That’s what I eventually figured out once you mentioned the first-order derivative condition, but thank you for confirming, I appreciate it.
No, it’s not clipped (in the meantime, I checked with RawDigger too), but with “luminance” preservation, not even a threshold of +6 EV spares it. With “RGB power norm”, it seems fine as long as the latitude is sufficiently narrow. I’ll see if I can send you the RAW somehow.
Look at your histogram… What you have here is a severe white balance problem. Fix it, and everything behaves. Also, you don’t need reconstruction at all, because, indeed, everything is correct and reconstruction, by design, propagate details from the neighbouring areas.
As a side note, using luminance on non-white-balanced images will always fail. White balance defines your RGB color space as much as your ICC profile, and luminance is computed from that RGB space. If the white balance is not properly set, your whole color space is as bad as if you applied a wrong color profile, and the luminance is wrong as well.
White balance is fine for the overall image. The crop is taken from a shaded area. If this area is neutralized, then the part of the image that is in the sun looks much too warm.
Here is the overall image (with the faces blurred):
Something I don’t understand is how the white T-shirt ends in the peak luminance area when it’s obviously not the image peak luminance.
Anyway, to fix varying white balance, you can use the color balance : neutralize the highlights white balance with the “slope/gain” hue, neutralize the shadows balance with the “offset/lift” hue, then maybe finish with “gamma/power”. That will help get achromatic greys all over the range.
The whole pipeline relies on the assumption that greys are achromatic under the working illuminant. If that condition is not met, any saturation adjustment will shift hue as well (because the saturation is the distance between current color and the closest achromatic grey shade), in unpredictable ways and the pipe will break at various places. Once you have ensured that overall condition, you may grade your image in an artistic way and move (carefully) from that neutral base to tinted greys to match your artistic intent, but always keep in mind that you are pushing the pipe out of its comfort zone.
@anon41087856 This workflow would only apply to new imports and or maybe unedited files??
I switched it on and I think some of my older edits may have been altered…I need to experiment more but I was just asking to clarify the operation and triggers…
I think this should be fixed in current master. The new automatic workflow (exposure/filmic) should now only auto-apply to new edits and discarded history stacks.
I have a question regarding selecting “scene referred” at the autoapply pixel workflow option.
Aurélien’s video and also the tooltips indicate that this should use “exposure” and “filmic” when starting a new edit of an image.
Unfortunately my install (master 3.1.0-git2144) seems to behave different:
If I have checked this option and create a “virgin” duplicate of an image it applies “Filmic” AND “basecurve” !!
If I re-import the images, then “exposure” and"Filmic" are used. So there it looks fine. But I would also expect this behavior when I add a virgin copy of an image for a new edit.
Has anybody seen the same behavior? Am I expecting something wrong here?
dt 3.1.0+2118~gee137f589, Ubuntu 18.04
For me it works as expected. Filmic applied and no basecurve when creating a “virgin” duplicate with duplicate manager.
Did you check if in preferences → processing you accidentally selected auto-apply per camera basecurve presets ?
Edit : Sorry, I made a mistake. I just checked again, the setting I mentioned has no influence. And I could reproduce your issue :
Launch darktable with setting “display referred”
Create a duplicate with duplicate manager : everything is fine, basecurve applied
Change workflow to “scene referred”
Create another duplicate : basecurve AND filmic applied !
Workaround : Exit and relaunch dt after changing the workflow setting.
thank you for your input and also confirmation.
Will take a deeper look here, but have the feeling that something is a bit inconsistent. Had the impression, that without restart the changes were somewhat done halfway (as basecurve and filmic) were applied. I would have expected that NO change would be done without restart …
Will play a bit more around and see if I can find a pattern here …
You may be right but then if you’re not restarting after making any of these changes then I suspect that any adverse or inconsistent consequences should be unsupported.
I saw the “needs a restart” in the tooltip but I misinterpreted it. I thought that it refers to “display referred” only. Perhaps putting “needs a restart” on top of the tooltip could make things clearer.
Did I ask to get such supported? But I think that such inconsistent behavior is for sure not something you want to see in a software. So if it can be omitted it should be. That’s why I asked for other experiences before filing a bug here.
Even after relaunching, I did come across an old image that, when opened, had both filmic and base curve applied. I assume that it already had base curve enabled previously and that exposure+filmic were applied on top because of having selected the scene-referred workflow.
For now, I will personally select “none” for “auto-apply pixel workflow defaults” and enable filmic manually to ensure consistency.
(Also, I am not sure that I see why exposure is automatically applied with +1 EV specifically. That seems to assume that middle grey falls at a specific raw level below sensor saturation (3.5 stops, right?), but there is no reason for that to be the case, and using in-camera metering, that’s going to vary a lot from camera to camera. Apparently, some Panasonic cameras even have negative highlight headroom, meaning that if you expose for a 18 % reflectance card, then 100 % is already beyond sensor saturation.)
Depends what version of master you are running. This shouldn’t happen on current master - the filmic and exposure defaults should only be auto-applied for a new image or when you discard your history.
