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karsten_bruun_qvist

8 Messages

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268 Points

Sun, Apr 28, 2019 5:16 PM

LR Classic histogram error when using certain profiles

Today I noticed a confusing and quite substantial discrepancy, in the lower end, between the Histogram in the develop module's top section and the histogram shown in Tone Curve section of the develop module (see photo) in LR Classic ver. 8.2 (Win). Of the two, the first suggested that the image was quite far from having a black point - which is not correct. 
On closer inspection I realized that this phenomenon was related to the profile Modern 8 having been applied to the image. Smaller discrepancies were observed with profiles Modern 9 and 10.
Similar problems/discrepancies were observed with several images.


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2 years ago

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andrew_rodney

1.9K Messages

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22.8K Points

2 years ago

There's a discrepancy because they are differing kinds of Histograms. One is a full color Histogram, the other a Luminance Histogram (brightness based on Lstar) and further, the horizontal 'size' (scale) differ. Might be nice if they were the same size and matched but how that might negatively affect the use of the curves could be raised. 

Author “Color Management for Photographers"

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karsten_bruun_qvist

8 Messages

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268 Points

Thanks Andrew! My main problem here is that there is a big gab to the left, indicating that noting is black in the image in the 'normal' histogram. This quite simply isn't correct, and can cause confusion when making tonal adjustments.
The tone curve histogram on the other hand reflect the truth, at least in regards to black point, in this case.
Also, the issue is not observed with most profiles, leading me to believe that there is an unintended 'bug' at operation.

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2 years ago

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andrew_rodney

1.9K Messages

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22.8K Points

Yeah, that is odd that the top shows there's no 'black' in such a large area while the lower one does. You see this on all images? Raw or rendered? 
This is a TIFF, it's absolutely got black (RGB zero) and both Histograms do show it as such:

Author “Color Management for Photographers"

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2 years ago

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todd_shaner_6660895

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2.3K Messages

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38K Points

Those camera profiles contain a tone curve setting with the black point raised vertically as shown below. This prevents moving the black point further to the left and was done on purpose to establish a specific "creative" rendering (hazy blacks).

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2 years ago

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