What do truncated Histogram spikes indicate

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I teach a class in fine art printing. During my last class we were looking at an image in LightRoom CC Classic and someone asked why the midtone spike in the image histogram was exceeded the top limit. So, it was cut off at the top. Since then, I have noticed this is rather common. But, I have no idea why it is or what it indicates. The response appear to be out of the graphic range of the histogram. But, so what?

histogram

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asked 1 hour ago

Paul Schillinger

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up vote
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down vote

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I teach a class in fine art printing. During my last class we were looking at an image in LightRoom CC Classic and someone asked why the midtone spike in the image histogram was exceeded the top limit. So, it was cut off at the top. Since then, I have noticed this is rather common. But, I have no idea why it is or what it indicates. The response appear to be out of the graphic range of the histogram. But, so what?

histogram

share|improve this question

asked 1 hour ago

Paul Schillinger

111

New contributor

Paul Schillinger is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

add a comment | 

up vote
2
down vote

favorite

up vote
2
down vote

favorite

I teach a class in fine art printing. During my last class we were looking at an image in LightRoom CC Classic and someone asked why the midtone spike in the image histogram was exceeded the top limit. So, it was cut off at the top. Since then, I have noticed this is rather common. But, I have no idea why it is or what it indicates. The response appear to be out of the graphic range of the histogram. But, so what?

histogram

share|improve this question

asked 1 hour ago

Paul Schillinger

111

New contributor

Paul Schillinger is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

I teach a class in fine art printing. During my last class we were looking at an image in LightRoom CC Classic and someone asked why the midtone spike in the image histogram was exceeded the top limit. So, it was cut off at the top. Since then, I have noticed this is rather common. But, I have no idea why it is or what it indicates. The response appear to be out of the graphic range of the histogram. But, so what?

histogram

histogram

share|improve this question

asked 1 hour ago

Paul Schillinger

111

New contributor

Paul Schillinger is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

asked 1 hour ago

Paul Schillinger

111

New contributor

Paul Schillinger is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

share|improve this question

asked 1 hour ago

Paul Schillinger

111

New contributor

Paul Schillinger is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 1 hour ago

Paul Schillinger

111

asked 1 hour ago

Paul Schillinger

111

111

New contributor

Paul Schillinger is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

New contributor

Paul Schillinger is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

Paul Schillinger is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

add a comment | 

add a comment | 

1 Answer
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It doesn't exceed the top of the histogram scale. That may appear common, only because histograms are always normalized. Data is intentionally scaled so that the peak value reaches the top (this shows low values better). And the exact count is unimportant. The range of distribution is the only thing important.

So all histograms approximately reach the full height possible (some one data value reaches the top). A histogram consisting of one spike of all pixels with only a single value will reach the top (clipping for example). Or a smooth histogram with a very wide full even range will also reach the top. However, some extreme rounding of data counts is of course necessary, because there are megapixels of values, but only a few possible pixels of histogram video display to show it. Any flat top of a peak is due to this necessary rounding.

As tonal things are adjusted, the heights may jump around, because the height does NOT represent brightness, it represents a count of pixels with that brightness, normalized to reach the top.

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edited 11 mins ago

answered 43 mins ago

WayneF

9,2361923

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  I think this answer is clearer than those in the similar question photo.stackexchange.com/questions/2913/…
  – dmkonlinux
  34 mins ago
  

  
  
  
  

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

active

oldest

votes

active

oldest

votes

up vote
5
down vote

It doesn't exceed the top of the histogram scale. That may appear common, only because histograms are always normalized. Data is intentionally scaled so that the peak value reaches the top (this shows low values better). And the exact count is unimportant. The range of distribution is the only thing important.

So all histograms approximately reach the full height possible (some one data value reaches the top). A histogram consisting of one spike of all pixels with only a single value will reach the top (clipping for example). Or a smooth histogram with a very wide full even range will also reach the top. However, some extreme rounding of data counts is of course necessary, because there are megapixels of values, but only a few possible pixels of histogram video display to show it. Any flat top of a peak is due to this necessary rounding.

As tonal things are adjusted, the heights may jump around, because the height does NOT represent brightness, it represents a count of pixels with that brightness, normalized to reach the top.

share|improve this answer

edited 11 mins ago

answered 43 mins ago

WayneF

9,2361923

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  I think this answer is clearer than those in the similar question photo.stackexchange.com/questions/2913/…
  – dmkonlinux
  34 mins ago
  

  
  
  
  

add a comment | 

up vote
5
down vote

It doesn't exceed the top of the histogram scale. That may appear common, only because histograms are always normalized. Data is intentionally scaled so that the peak value reaches the top (this shows low values better). And the exact count is unimportant. The range of distribution is the only thing important.

So all histograms approximately reach the full height possible (some one data value reaches the top). A histogram consisting of one spike of all pixels with only a single value will reach the top (clipping for example). Or a smooth histogram with a very wide full even range will also reach the top. However, some extreme rounding of data counts is of course necessary, because there are megapixels of values, but only a few possible pixels of histogram video display to show it. Any flat top of a peak is due to this necessary rounding.

As tonal things are adjusted, the heights may jump around, because the height does NOT represent brightness, it represents a count of pixels with that brightness, normalized to reach the top.

share|improve this answer

edited 11 mins ago

answered 43 mins ago

WayneF

9,2361923

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  I think this answer is clearer than those in the similar question photo.stackexchange.com/questions/2913/…
  – dmkonlinux
  34 mins ago
  

  
  
  
  

add a comment | 

up vote
5
down vote

up vote
5
down vote

It doesn't exceed the top of the histogram scale. That may appear common, only because histograms are always normalized. Data is intentionally scaled so that the peak value reaches the top (this shows low values better). And the exact count is unimportant. The range of distribution is the only thing important.

So all histograms approximately reach the full height possible (some one data value reaches the top). A histogram consisting of one spike of all pixels with only a single value will reach the top (clipping for example). Or a smooth histogram with a very wide full even range will also reach the top. However, some extreme rounding of data counts is of course necessary, because there are megapixels of values, but only a few possible pixels of histogram video display to show it. Any flat top of a peak is due to this necessary rounding.

As tonal things are adjusted, the heights may jump around, because the height does NOT represent brightness, it represents a count of pixels with that brightness, normalized to reach the top.

share|improve this answer

edited 11 mins ago

answered 43 mins ago

WayneF

9,2361923

It doesn't exceed the top of the histogram scale. That may appear common, only because histograms are always normalized. Data is intentionally scaled so that the peak value reaches the top (this shows low values better). And the exact count is unimportant. The range of distribution is the only thing important.

So all histograms approximately reach the full height possible (some one data value reaches the top). A histogram consisting of one spike of all pixels with only a single value will reach the top (clipping for example). Or a smooth histogram with a very wide full even range will also reach the top. However, some extreme rounding of data counts is of course necessary, because there are megapixels of values, but only a few possible pixels of histogram video display to show it. Any flat top of a peak is due to this necessary rounding.

As tonal things are adjusted, the heights may jump around, because the height does NOT represent brightness, it represents a count of pixels with that brightness, normalized to reach the top.

share|improve this answer

edited 11 mins ago

answered 43 mins ago

WayneF

9,2361923

share|improve this answer

share|improve this answer

edited 11 mins ago

edited 11 mins ago

edited 11 mins ago

answered 43 mins ago

WayneF

9,2361923

answered 43 mins ago

WayneF

9,2361923

answered 43 mins ago

WayneF

9,2361923

9,2361923

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  I think this answer is clearer than those in the similar question photo.stackexchange.com/questions/2913/…
  – dmkonlinux
  34 mins ago
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  I think this answer is clearer than those in the similar question photo.stackexchange.com/questions/2913/…
  – dmkonlinux
  34 mins ago
  

  
  
  
  

2

2

I think this answer is clearer than those in the similar question photo.stackexchange.com/questions/2913/…
– dmkonlinux
34 mins ago

I think this answer is clearer than those in the similar question photo.stackexchange.com/questions/2913/…
– dmkonlinux
34 mins ago

add a comment | 

Paul Schillinger is a new contributor. Be nice, and check out our Code of Conduct.

 

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