Luminous Landscape Forum
Raw & Post Processing, Printing => Adobe Lightroom Q&A => Topic started by: button on April 04, 2008, 12:17:17 pm
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Hello everyone,
My question applies to a RAW image that, when opened in AL or ACR, shows slight highlight clipping (not completely blown). What is the difference between simply dropping the exposure slider to bring those highlights back (and then correcting the then darkened image with brightness or curves adjustments), as opposed to using the reovery slider to do so?
Thanks,
John
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The "exposure correction" is a linear adjustment, it affects the entire range. "Recovery" reduces only the top range.
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The "exposure correction" is a linear adjustment, it affects the entire range. "Recovery" reduces only the top range.
[a href=\"index.php?act=findpost&pid=187034\"][{POST_SNAPBACK}][/a]
So, given my hypothetical problem, which approach would you use?
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Hi!
Highlight recovery tries to calculate color and density from the unclipped channels. Keep in mind that ACR/LR has access to all information from the sensor. Doing white balance the channels are shifted, for that reason more information may actually be available then you can see.
Erik
Hello everyone,
My question applies to a RAW image that, when opened in AL or ACR, shows slight highlight clipping (not completely blown). What is the difference between simply dropping the exposure slider to bring those highlights back (and then correcting the then darkened image with brightness or curves adjustments), as opposed to using the reovery slider to do so?
Thanks,
John
[a href=\"index.php?act=findpost&pid=187029\"][{POST_SNAPBACK}][/a]
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So, given my hypothetical problem, which approach would you use?
This depends on the actual image. Pulling down the highlights only reduces the contrast at the high end. This may or may not pose a problem, depending on the "distribution". The histogram shows, what can be done to achieve the best result; this depends on the other settings, mainly on the contrast setting.
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This depends on the actual image. Pulling down the highlights only reduces the contrast at the high end. This may or may not pose a problem, depending on the "distribution". The histogram shows, what can be done to achieve the best result; this depends on the other settings, mainly on the contrast setting.
[a href=\"index.php?act=findpost&pid=187046\"][{POST_SNAPBACK}][/a]
Hmmm... this is more complicated than I thought. Would you mind giving me some examples, if feasible? Up until this point, I would simply use the recovery slider to tame those slightly overexposed (not totally blown) highlights. What I'm gathering is that the highlight recovery tool compresses highlights, in addition to reconstructing lost data based on the intact channels. Is this correct?
Thanks,
John
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I guess the heart of the matter is this: If highlights are overexposed (but not blown), does the use of the recovery tool introduce artificial data, or does it simply compress the highlights? If so, then using the exposure tool to bring down the overall exposure and then "fixing the historgram" with the curves tool seems like the better solution.
John
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What is the difference between simply dropping the exposure slider to bring those highlights back (and then correcting the then darkened image with brightness or curves adjustments), as opposed to using the reovery slider to do so?
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The latter guarantees to touch nothing below the highlights (you may have to slightly lighten the "light tones" of the curve in some cases, but nothing more).
The former can also achieve the same goal, or very close, after more adjustments ;o).
I'd think that in both cases, ACR/LR will try to guess the missing data the same way... but we'd need an insider to be sure of that.
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Both negative exposure compensation (setting the Exposure control to a negative value) and the recovery slider will perform highlight recovery if needed. The primary difference between the tools has been pointed out earlier in the thread: EC will affect the entire range (including the midtones, where it's most noticeable) whereas recovery is limited to the top range.
Using only the recovery slider is similar (but not identical) to using negative EC but increasing Brightness. In both cases, you are effectively compressing the highlights, and the downside is that you may lose fine tonal distinctions in the highlights.
If you use only negative EC then you'll generally see more tonal distinctions in the highlights but the midtones will become darker and you'll see less tonal distinctions in the shadows. There's a tradeoff here: whenever you stretch tonal values in one place you'll compress tones elsewhere (at least when applying a simple 1D tone curve).
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Hi,
My practical approach:
1) Try to get it right in exposure (check histogram)
2) Check histogram in Lightroom
a) Reduce exposure if I can without losing shadows
Use recovery to improve separation in highlight
3) Adjust blacks
4) Add fill light
5) Adjust brightness
6) Adjust contrast
7) Adjust vibrance
After this:
1) Reconsider image
2) Possibly iterate 2-7, preferably after taking a snapshot
3) Doing adjustment with TAT for tone curve and saturation
A hint is that you can always try "auto", it often gives decent setting for exposure and recovery. If you use auto you would probably need to adjust brightness and add fill light if needed.
Best regards
Erik
Hello everyone,
My question applies to a RAW image that, when opened in AL or ACR, shows slight highlight clipping (not completely blown). What is the difference between simply dropping the exposure slider to bring those highlights back (and then correcting the then darkened image with brightness or curves adjustments), as opposed to using the reovery slider to do so?
Thanks,
John
[a href=\"index.php?act=findpost&pid=187029\"][{POST_SNAPBACK}][/a]
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I guess the heart of the matter is this: If highlights are overexposed (but not blown), does the use of the recovery tool introduce artificial data, or does it simply compress the highlights? If so, then using the exposure tool to bring down the overall exposure and then "fixing the historgram" with the curves tool seems like the better solution.
John
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Bruce Fraser's book on ACR asserted that ACR attempts to magic up any missing data, based on the channels that it has data for. i.e. if the red channel is blown, but G&B still having workable data, it will try to best guess data for the red channel. Obviously the degree of accuracy decreases if you have 2 blown channels, and if you've got lost all 3, then it's just a work of fiction.
I don't know if that is still the case - this was for ACR 2.x I believe. This was, I think, talking about using the exposure slider to recover highlights. I can't remember if ACR 2 had a recovery slider or not.
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The "exposure correction" is a linear adjustment, it affects the entire range. "Recovery" reduces only the top range.
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These [a href=\"http://luminous-landscape.com/forum/index.php?showtopic=24354&view=findpost&p=186076]Tone Curves[/url] from a post in another thread show the difference between the use of the exposure and recovery sliders to recover highlights. As is apparent, the tone curves are quite different in the midtones and shadows.
Bill
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Thanks, everyone, for the comments.
John
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