Lightroom: Automatic black/white clipping in curve tool

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It would be great if in presets (i.e. on import or applied to selected images) the left and right sides of the curve could be automatically adjusted to clip the blacks and whites automatically.

For me this is usually the only thing I have to do by hand to optimize an image. It is easy to do manually, but other tools can do it automatically and the images benefit a lot from it.

Also in combination with the auto adjustment this leads to punchier images right away.
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Julian Z

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Posted 5 years ago

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Rikk Flohr, Champion

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You can save curves as a preset in the Tone Curve panel. Does that help?
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Julian Z

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Thanks, but thats is not what I mean.

I think it would be useful, if LR can automatically(!) move the left and right side according the the histogram of the current image to clip, i.e. 0.1% of the value.

Functionality is actual quite simple: logic finds point where histogram is >level x and moves margin point there. The connection between start and end can be a line (linear) or a curve for softer or harder contrast, but in all cases it would be adapted automatically to the actual image.

Custom curves do not help, since they do not automatically adapt to the image.

I believe with this functionality, the default import of lightroom would significantly improve.

Such auto-clipping could be of course a speparate tool to leave the curve for other tasks.
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Rob Cole

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Julian - I agree with the spirit of your request, if not the letter.

i.e. what we often need, at least initially, is to keep the picture and tonal distribution as is, but just get rid of the dead space in the end ranges so it occupies full dynamic range.

Auto-tone is supposed to do that, but it does a lot more, and unfortunately completely screws up exposure a lot of the time in the process.

+1 to having an auto-toner which does what we want, but
-1 to having Lr set black/white point using the existing point curve, given the way the pipeline works.
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Rob Cole

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Beware that tone curve is applied after basics (internally, in the "pipeline").

And because basics have special intelligence in blacks/whites handling, I strongly recommend against using tone curve to establish black/white point before tapping the basics.

Obviously, to each their own and all, but what you're suggesting is certainly sub-optimal.

If you want punchier images after (exposure corrected) auto-toning, just pull the blacks slider to the left and/or bump contrast... Gazoo has some intelligent (and customizable) auto-toning presets if you're into that sort of thing.

Cheers,
Rob
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Stefan Keller

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"And because basics have special intelligence in blacks/whites handling"

this could do the same, but where is this intelligence?
sometime "auto tone" works fine sometimes bad
it would be good to only touch blacks and whites in auto tone
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Rob Cole

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Most of my response is in the post below. but a PS here: I realize auto-toner gets crazy with the exposure sometimes, and it includes cropped-out region when it shouldn't... and it has some other personality traits which don't suit me so well either, which is why I wrote my own auto-tone tuner. It's far from perfect too, since it doesn't improve on setting reasonable exposure in the first place, and still doesn't have the ability to simply smoothly expand histogram to fill..., but I certainly get better results with it than without it (Gazoo's "Seat Well / Enhance Contrast" intelligent preset which is designed to be used in conjunction with auto-tone).
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Rob Cole

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Alt-click the (!) in Lr4 with a (barely) full dynamic range image selected and watch the end-points in the histogram get re-shaped. Also, crank the exposure and whites slider up and back and you can see how they "have your back", so to speak. To summarize:

* Exposure: roll-off intelligence (tones will gang up against the right wall but not spill over too much).
* Whites: you can brighten the whites/highlights without excessive clipping, or color wonkiness due to partial channel clippage.

You lose all of that when you bring the white point in using point curve.

And, perhaps even more importantly, slider behavior is image adaptive and strongly tied to exposure - if you brighten by using point curve to bring clipping point in, you cripple all your basic sliders.

Don't get me wrong, there are times when bringing the right-hand point inward can be a really good thing - like when +exposure and/or +whites is causing an excessive ganging up against a virtual wall prematurely. Hard to explain - I've posted screen shots before in other threads though.

Bottom line: best to reach the limits of the basics first before augmenting with point curve.

PS - I strongly agree with the need for a black&whites-only auto-toning feature, which is why it exists in Gazoo:

Beware though: for best results it should be followed up immediately with a manual exposure adjustment, and all the rest, since it is *not* the same as setting black & white point like you're thinking about via tone/point curve. *all* pv12 adjustments are part of a team, there is no auto-toning adjustment that is very much akin to setting black/white points via curve. - maybe someday...

PS - You can also shift-double-click blacks and whites slider labels in dev module to manually set auto-toned blacks and/or whites values.

Cheers,
Rob
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Stefan Keller

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"shift-double-click blacks and whites"
thats fine!,
but adobe, why do you hide those gems in the UI ????

"Alt-click the (!)"
what shall I do ????
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Rob Cole

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"Alt-click the (!)" - I meant "convert from legacy process version to PV2012".

Sorry for being cryptic.

PS - in legacy process versions one could make presets to set auto-toned values for any combination of basic sliders, but that went away in PV2012 for some reason.

Note for future: Remember the 'Alt' key, luke! ;-)
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Stefan Keller

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oh I shortly guessed that, but hoped for another hidden gem :-)
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Julian Z

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Thank's for all that information. I really didn't think that the curve is applied after the basic adjustment - although I am not sure which drawbacks this could have.
I expect the curve is applied in 16bit color mode, so there is enough information to work with, unless exposure, white or black have already caused clipping.

I agree to what was said above, it would be good to only touch blacks and whites in auto tone. At least optionally.
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Rob Cole

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PV2012 is designed so that the behavior of the shadows slider (for example), is tied to tonal distribution *and* exposure setting. So if you don't crank up the exposure, you won't get good performance from the shadows slider. If you are *not* (yet anyway) messing with the basics sliders, then setting white/black points using point curve may be a fine way to get you through the day, but when you do return to optimize the basics, be sure to *start* by releasing the end-points of the point curve, for the reason just mentioned, and also the previously mentioned reason: to take advantage of basics intelligence for blacks & whites tone/color handling.

I often use a "U" shaped curve in conjunction with PV2012. Why? because I sometimes like lower-key photos, yet ample exposure (via basics slider) must be provided to "prime" the other PV2012 basics sliders - i.e. use PV2012 exposure slider to add light, and tone curve to remove it, instead of the other way around.

Another reason to not use point curve for bringing in whites/blacks: Twisted camera calibration profiles are tuned for full spectrum histogram, i.e. hues that vary with luminance assume full luminance range (not "artificially stretched" after the fact via point curve).

R
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Rob Cole

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Be careful what you ask for...

Gazoo (@v4.17) now has auto-black/white-point curve presets:



I still don't recommend them as a substitute for basic settings, but as always: it's your call.

Rob