Lightroom Clipping Indicators

[Schewe]

Hope this isn't getting off topic, but I see the highlight clipping indicator change when adjusting the brightness slider. I thought the brightness control was not supposed to affect the extremes.

Brightness used only by itself will not clip...if you are seeing clipping when adjusting Brightness, it means some other adjustment is actually pushing the boundaries and Brightness is being added to the other adjustment.

[fdisilvestro]

Values close to the maximum (i.e 252 -254 in 8 bits) could become 255 by adjusting brightness and this will activate the indicators. This also could be due to rounding errors. Anyway, I have seen this behavior too.

Something to consider is that brightness does this in a smooth way, so there should not be an abrupt transition as in a regular blocked highlight.

[Guillermo Luijk]

I guess clipping warning works with a threshold. So although some highlight area could not be strictly clipped, for high Brightness values tonal compression could be so strong that wide areas as a whole reach the clipping warning threshold.

This is ACR's brightness control represented as curves:



I guess LR is similar (BTW if someone posts 2 images from LR, before/after, I will calculate the transfer curve. The only condition is that only the control under study is applied, any other setting must be set to 0, neutral,...:

[David Eichler]

I guess clipping warning works with a threshold. So although some highlight area could not be strictly clipped, for high Brightness values tonal compression could be so strong that wide areas as a whole reach the clipping warning threshold.

This is ACR's brightness control represented as curves:



I guess LR is similar (BTW if someone posts 2 images from LR, before/after, I will calculate the transfer curve. The only condition is that only the control under study is applied, any other setting must be set to 0, neutral,...:

Guillermo's graph provides a nice illustration of the answer to my question, assuming that Lightroom's brightness control performs similarly to ACR's.

[madmanchan]

Yes, LR's controls are exactly the same as ACR's, including Brightness.

As noted earlier, the clipping indicators will be slightly conservative because of the roundoff.  So in 8-bit space, if you had something that was like 254.6, then technically it hasn't clipped yet, but for the purposes of the clip indicator it'll get rounded off to 255, and hence shown as clipping.  Bottom line is that if you see the indicator, then you've either clipped data or you're very close to clipping data.

I am indeed aware of the request to have a better way to preview clipping in other spaces.  I hope to be able to offer a solution in the future.

[bjanes]

Eric, the one million euro question is: why Adobe decided not to adapt the histogram to the chosen output colour profile like ACR does?

Guillermo,

Reference to one of the early Lightroom podcasts (#6 as I recall), includes a discussion between Mark Hamburg (the architect of LR) and Thomas Knoll (the architect of Phososhop and ACR) where they discuss histograms, color spaces, info readout, etc.  Mr. Knoll suggested that LR could allow the user to select the color space for output rendering as does ACR, but Mr. Hamburg wanted to keep things simple.

Once the decision was made, internal politics at Adobe would make criticsm of that decision by Adobe engineers rather awkward.

Regards,

Bill

[Peter_DL]

... but Mr. Hamburg wanted to keep things simple.

Understandable,
considering that neither LR nor ACR offer specific tools to defeat saturation clipping from gamut conversion.
Without intending to overemphasize this aspect, pRGB to aRGB or sRGB is still among the few reasons where I occasionally prefer to resort to Photoshop.

Peter

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