Lightroom: auto-tone under-exposure

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  • Updated 5 years ago
Recently I tried auto-tone again, and the result was *way* under-exposed (big space on right side of histogram).

My first choice would be a remake of auto-toning, which allows a user to dial in a style and a few general guidelines, and have a toned output that hits very close to the target (savable as an auto-toning preset). See related idea: http://feedback.photoshop.com/photosh...

If that kind of fix is not in the cards for Lr4, please at least fix the auto-tone exposure computation.

If the auto-tone exposure determination is by design (at the moment, I can't imagine it), then please educate us...

(sometimes the result is over-bright instead of under-exposed, but one step at a time here...)

Whether the current behavior is by design or faulty, I'd like to see the ability to auto-tone in such a fashion that full use of the dynamic range is accomplished (no space and minimal clipping at the endpoints).

Note: The blacks computation seems fine, its the exposure computation that is off.

Thanks,
Rob
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Rob Cole

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Posted 5 years ago

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Steve Sprengel, Champion

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I am not seeing auto-toning guessing overly dark unless a large part of the image is supposed to be brighter than average, like a bird against a cloudy sky or a closeup of a bug on a white daisy where the petals fill most of the frame. A bride in a white wedding dress would probably have the same problem if the dress filled most of the frame.

Can you provide a link to a RAW file with the issue?
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Rob Cole

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Example Histogram (following a "Reset" and an "Auto-Tone"):


Corresponding jpeg:


Raw File:
http://www.robcole.com/_temp/20110919...
(if Windows, right-click and select "Save Link As")

PS - there have been other complaints about this, from time to time, in this forum or that, so I know its not just me...
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Rob Cole

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Note: this behavior is not exhibited on all or even most images, just some...

I have a theory:

One thing about this image is the red-channel extends way beyond the blue and green - I think that may be what is steering Lightroom off course.

Rob
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Steve Sprengel, Champion

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The NEF link, above, is giving a 404 error. Did you take it down, already?

Also, I could imagine that the orange flowers might be detected as skin and therefore made midtone instead of bright. Do you have something that can't be misinterpreted as skin?
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Rob Cole

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Right-click it and choose "Save Link As".

Lightroom's auto-toning algorithm includes skin-tone detection?, really??
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Steve Sprengel, Champion

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I did that, among other things, and at best I get a 1.6KB text file with the 404-error text in it:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
The page cannot be found

BODY { font: 8pt/12pt verdana }
H1 { font: 13pt/15pt verdana }
H2 { font: 8pt/12pt verdana }
A:link { color: red }
A:visited { color: maroon }

The page cannot be found


The page you are looking for might have been removed, had its name changed, or is temporarily unavailable.


Please try the following:


  • Make sure that the Web site address displayed in the address bar of your browser is spelled and formatted correctly.

  • If you reached this page by clicking a link, contact
    the Web site administrator to alert them that the link is incorrectly formatted.

  • Click the Back button to try another link.


HTTP Error 404 - File or directory not found.
Internet Information Services (IIS)




Technical Information (for support personnel)


  • Go to Microsoft Product Support Services and perform a title search for the words HTTP and 404.

  • Open IIS Help, which is accessible in IIS Manager (inetmgr),
    and search for topics titled Web Site Setup, Common Administrative Tasks, and About Custom Error Messages.

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Rob Cole

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Strange. What OS/Browser? (it works fine for me win7/64+Firefox).
Standby and I'll post a zip instead...
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Steve Sprengel, Champion

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Win7-64 Professional, with Chrome 14, FF 7, IE 9 all doing the same thing.
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Rob Cole

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I'm running FF 6(.02) - there's a seven?

Anyway, maybe its your ISP trying to protect you from object files or something - I got no clue - any theories?
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Here is a screen-capture of the Fiddler traffic showing the Headers for both the Get and Response:
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Rob Cole

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I see what's happening, I just don't see why. The file is there, and I have no problem downloading it using firefox, using right-click. I *do* get the same error as you if I just click it, which I don't understand either...

*** Try the link above again (its a zip now, instead of NEF) - better?
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I'm getting a 19MB file, this time, so it's working better.
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Rob Cole

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That would be it... :-)
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The histogram looks ok on my computer, with the red extended up into the top 4th a bit, not like yours. Also if you do Auto in ACR and have sRGB selected as your output profile, the red area is almost all the way over to the right. I am using Adobe Standard in Lightroom. Are you using some non-standard camera profile, or something other than As Shot as the WB?
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Rob Cole

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Yes, I'm using a non-standard profile, so that probably accounts for the differences we see here, otherwise your result looks very similar to mine - underexposed according to my eye, and according to NX2, whose auto-levels step produces an image far more exposed. Maybe NX2 is willing to do independent channel compression, whereas Lightroom isn't.

Are you saying you get different results using ACR via Photoshop instead of Lightroom? or, are you just getting a different histogram after exporting an sRGB file (I exported AdobeRGB and the histogram looks "about" the same as it does in Lightroom before exporting).
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Rob Cole

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I'll do some more checking over time, but at this point I'm pretty convinced that the problem (in this example) is caused by the overly luminous red channel shifting the whole histogram leftward. I'm not sure why that doesn't show in the Lightroom histogram, but its obvious in the NX2 histogram (and I guess in the other sRGB one Steve was looking at).
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that exposure looks pretty spot on to me, I'd probably, tweak the vibrance, but the exposure of the petals is good. I'd also take the background down, but that is not the issue.
What are your feelings about the exposure, is it too low, or just the histogram looking incorrect?
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Rob Cole

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Here is how I finished this photo in Lightroom (jpeg posted here is AdobeRGB):


And here is the corresponding histogram in Lightroom:


Interestingly enough, here is the histogram for that same photo (with no further adjustments, after export (AdobeRGB)) in ACDSee:


I assume this is what Steve Sprengel was talking about earlier (sRGB).

So I think what's happening is Lightroom is responding to the "overly luminous" red-channel in its auto-toning algorithm, despite not being represented in the histogram for some reason.

btw. these are "Stars of Bethlehem" and are a very saturated and screamingly bright orange in real life - I wanted that to come across...
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After AutoToning the NEF in ACR, still in ACR, I was looking at differences in the histogram after setting the output colorspace in ACR to ProPhotoRGB and sRGB, where the sRGB version had the red up near the clipping point, but not quite. This means that brightening the reds much more than the deemed-too-dark value from AutoTone would have made the hue shift as the red-channel clipped when converted to sRGB. I wondered if Adobe's RAW AutoTone was trying to protect reds from clipping as if exported in sRGB when LR's histogram is based on a much wider ProPhotoRGB with an sRGB gamma curve or whatever the oddness is that makes the histogram non-comparable to any other histogram.

To simulate the ACR sRGB-export histogram in LR and ACDSee, you would export the AutoToned image as an sRGB JPG and look at its histogram in ACDSee.
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Rob Cole

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Yeah - I think you've nailed it Steve.

So, the only question I have in my mind is:

- Would it be worthwhile for Lightroom's auto-toning algorithm to be tweaked to take this sort of thing into account. I just checked DxO's auto-toning algorithm and it works more like NX2's: producing a more exposed image in this case.

I feel a lot better about this now, just because I think I understand what's happening, but the bottom-line for me is that I rarely use Lightroom's auto-toning due to frequently under-exposed (or sometimes over-bright) results.

My apology in advance to those who've tired of hearing it, but I think the ability to influence the auto-toning would be a big boon to productivity - dial in some guidelines (or select an auto-toning style preset) and away we go - image done unless it needs special tweaking of color/tone-curve or local correction...

Absolute presets, and even relative presets just don't cut it for this kind of thing - the algorithm needs to have intelligence, results to be based on image analysis and discovery, not blind...

To drive the point home: I often find myself doing the same things over and over again, but there is no way to capture it in a preset, since adjustment depends on starting point. I really don't know how doable it would be to automate this, but its worth thinking about anyway...

Rob