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Author Topic: PSE ACR histogram highlight clipping point moves right with increased exposure  (Read 3254 times)

digitaldog

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Re: Miss-leading Histograms
« Reply #40 on: April 15, 2020, 02:29:05 pm »

+1

Without the proper context, histograms can be quite misleading. Here is an example. A red flower was photographed with the Nikon D850 with the camera set to AdobeRGB and the Picture Control to flat.

The camera histogram shows a nearly ideal ETTR exposure. Looking at the histogram in ACR Process Version 5 with the Adobe Color profile and rendering into AdobeRGB, the histogram is slightly to the left of the camera histogram. However, looking at the raw histogram in Rawdigger demonstrates that the red channel is more than 2 EV short of clipping. The white balance coefficients are added to the Rawdigger histogram. Note that the red channel is multiplied by 1.90 for white balance.

Finally, rendering into sRGB with the same settings in ACR shows prominent clipping in the red channel.

Bill
+1; Histograms can lie, a lot as outlined. Especially with raw data and a Histogram of rendered data that isn't reporting the actual data. A Histogram of a current rendering that only tells us about that current rendering (in this case, Saturation clipping as explained of a single channel) which has nothing to do with the raw let alone highlight clipping.
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Frans Waterlander

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Re: Miss-leading Histograms
« Reply #41 on: April 15, 2020, 02:47:38 pm »

+1; Histograms can lie, a lot as outlined. Especially with raw data and a Histogram of rendered data that isn't reporting the actual data. A Histogram of a current rendering that only tells us about that current rendering (in this case, Saturation clipping as explained of a single channel) which has nothing to do with the raw let alone highlight clipping.
You still don't get it, do you? As I stated early on, the issue that I brought up has nothing to do with how well the histogram represents the original image data. It had everything to do with what looked like a weird shift in the clipping level, explained by some helpful people to be highlight recovery algorithms in action.
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digitaldog

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Re: Miss-leading Histograms
« Reply #42 on: April 15, 2020, 02:59:15 pm »

You still don't get it, do you? As I stated early on, the issue that I brought up has nothing to do with how well the histogram represents the original image data. It had everything to do with what looked like a weird shift in the clipping level, explained by some helpful people to be highlight recovery algorithms in action.
You still don't get it. What was told to you by three people have nothing to do with Highlight clipping. Further still, you don't get what three four people have told you; Histograms lie (like the leader of the free world  ;) ).

TOPIC: PSE ACR histogram highlight clipping point moves right with increased exposure
When you increase exposure in the Photoshop Elements ACR converter, the highlight clipping point shows up when you start to blow out the highlights, as you would expect.

What I do know is that the highlight clipping line of the ACR histogram moves to the right when increasing Exposure and that move is confirmed when playing with Levels after RAW conversion.

This is not an issue of whether or not the histogram in the Adobe Camera RAW (ACR) converter faithfully represents the underlying data, but why the highlight clipping level is shifted to the right when the Exposure slider is moved to the right (as confirmed by using Levels after conversion).

Reply #26 on: April 08, 2020, 05:40:45 pm
Do you understand the differences between clipping highlights and clipping a single channel?
Answer as seen above: No.
« Last Edit: April 15, 2020, 03:11:57 pm by digitaldog »
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Frans Waterlander

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No, Andrew, you still don't get it. Highlight recovery algorithms and how they can be seen at work in the histogram and how I misinterpreted it as moving clipping levels is the issue.
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digitaldog

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Yes you misinterpreted! And by your own admission, guessed. Despite this being explained to you. As we’ve seen in the past and predicted you would in post #2. And #4!
« Last Edit: April 15, 2020, 03:36:28 pm by digitaldog »
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Frans Waterlander

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Yes you misinterpreted! And by your own admission, guessed. Despite this being explained to you. As we’ve seen in the past and predicted you would in post #2. And #4!
And you, sir, never understood what was really happening, but ranted on and on about basic histogram stuff, not at all applicable to this corner case of highlight recovery algorithms. Maybe you should work on some infrared shots and observe what happens to the ACR histogram under different process versions.
« Last Edit: April 15, 2020, 04:05:55 pm by Frans Waterlander »
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digitaldog

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And you, sir, never understood what was really happening, but ranted on and on about basic histogram stuff, not at all applicable to this corner case of highlight recovery algorithms.

As is so often the case, you've shown your readers you can't read what has been written correctly and described to you nor do you even understand the so called "basic histogram stuff" but you can only guess (stating it's an educated guess; hilarious and not so):
« Reply #21 on: April 08, 2020, 02:18:04 pm »
Side note: Raw CAN undergo highlight reconstruction (recovery) and how well is dependent on Process Version used. IF one channel of raw isn't clipped, but the other two are, ACR/LR can provide highlight recovery from the one channel. But NOT from anything done with Exposure slider being pushed to the right...


“Nothing in all the world is more dangerous than sincere ignorance and conscientious stupidity.” Martin Luther King
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Frans Waterlander

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As is so often the case, you've shown your readers you can't read what has been written correctly and described to you nor do you even understand the so called "basic histogram stuff" but you can only guess (stating it's an educated guess; hilarious and not so):
« Reply #21 on: April 08, 2020, 02:18:04 pm »
Side note: Raw CAN undergo highlight reconstruction (recovery) and how well is dependent on Process Version used. IF one channel of raw isn't clipped, but the other two are, ACR/LR can provide highlight recovery from the one channel. But NOT from anything done with Exposure slider being pushed to the right...


“Nothing in all the world is more dangerous than sincere ignorance and conscientious stupidity.” Martin Luther King

Well, that's reply #20 on my screen, but who's counting. And that side note is a good example of touching upon an subject, but not really explaining it. Yes, you touched upon the issue of highlight recovery, but claimed that had nothing to do with the Exposure slider. Francisco and Bill understood and explained it. Let me repeat that maybe you should work on some IR images and see what happens.
« Last Edit: April 15, 2020, 04:25:52 pm by Frans Waterlander »
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digitaldog

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Well, that's reply #20 on my screen, but who's counting.
And who’s not reading, understanding or accepting? You sir. That should be abundantly clear to those here that DO read and understand the predicted agenda outlined in post 2 and 4 and further.
Again, enough said to readers. As for non readers, you will continue.
Here it comes.....  ;D
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Frans Waterlander

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And who’s not reading, understanding or accepting? You sir. That should be abundantly clear to those here that DO read and understand the predicted agenda outlined in post 2 and 4 and further.
Again, enough said to readers. As for non readers, you will continue.
Here it comes.....  ;D

DO let us know what you find out if and when you work with some IR images.
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digitaldog

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DO let us know what you find out if and when you work with some IR images.
More proof you're not reading:
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fdisilvestro

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This is not an out of gamut issue, it is a case of really overblown raw channel. It it were a case of out of gamut for sRGB, the spike will disappear when reducing exposure. The more experienced photographers who never miss the correct exposure may have not experienced it, but lousy photographers as myself have experienced it plenty of times, so even if the LR histogram does not tell you the right picture about the raw data (use rawdigger for that). The "Moving spike" is a clear indication of overexposure beyond the capabilities of the highlight reconstruction.

As for the current Process version of LR compared to the old, yes, the highlight reconstruction is invoked automatically, but if you search in the history of LuLa posts by Madmadchan (Erik Chan), who knows a thing or two about LR, explains that the priority of the new process is to maintain the tone of the image, while the previous processes tend to introduce colour shifts.

Frans Waterlander

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...if you search in the history of LuLa posts by Madmadchan (Erik Chan), who knows a thing or two about LR, explains that the priority of the new process is to maintain the tone of the image, while the previous processes tend to introduce colour shifts.

How do I do that, Francisco? When I search for either Madmadchan or Erik Chan in the top level of this forum, the only hit I get is your post.
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digitaldog

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This Adobe engineer is named Eric Chan.
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fdisilvestro

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This Adobe engineer is named Eric Chan.

Oops! thanks for the correction, Apologies to Eric Chan.

fdisilvestro

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How do I do that, Francisco? When I search for either Madmadchan or Erik Chan in the top level of this forum, the only hit I get is your post.

Hi, you could go to Members -> Search for Members and look for this specific member and then search posts (I believe this only works for subscribers)
Otherwise look for PV2012 posts in the LR Subforum.

Here an example of a post by Madmanchan (Eric Chan) about this:
 
https://forum.luminous-landscape.com/index.php?topic=70852.msg561230#msg561230
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