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Another ETTR Discussion
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Jan 14, 2019 09:43:56   #
selmslie Loc: Fernandina Beach, FL, USA
 
rmalarz wrote:
I have it on very good authority that the histogram in ACR is from the RAW file. ...

Your "very good authority" is dead wrong!

Look at these displays of an image with a slight EBTR exposure. RawDigger shows that some of the blue and green pixels are between the 8000 and 16000 level - easily recovered.

Capture One (ACR would show the same information in the first histogram) just shows a tiny spike on the right - too small to reliably indicate whether the highlights can be reliably recovered.

Based on the information in the RawDigger plot I applied a -0.7 adjustment to the Exposure slider and the spike went away.

You need to find a more reliable authority.

Better yet, do this experiment yourself.

RawDigger information
RawDigger information...
(Download)

No adjustment - tiny spike on the right
No adjustment - tiny spike on the right...
(Download)

Exposure -0.7 adjustment - no spike
Exposure -0.7 adjustment - no spike...
(Download)

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Jan 14, 2019 10:00:41   #
rmalarz Loc: Tempe, Arizona
 
My very good authority is Jeff Schewe. Perhaps you'd like to argue with him. I'm sure he'd be fascinated with your data.
--Bob
selmslie wrote:
Your "very good authority" is dead wrong!

Look at these displays of an image with a slight EBTR exposure. RawDigger shows that some of the blue and green pixels are between the 8000 and 16000 level - easily recovered.

Capture One (ACR would show the same information in the first histogram) just shows a tiny spike on the right - too small to reliably indicate whether the highlights can be reliably recovered.

Based on the information in the RawDigger plot I applied a -0.7 adjustment to the Exposure slider and the spike went away.

You need to find a more reliable authority.

Better yet, do this experiment yourself.
Your "very good authority" is dead wrong... (show quote)

Reply
Jan 14, 2019 10:24:59   #
selmslie Loc: Fernandina Beach, FL, USA
 
rmalarz wrote:
My very good authority is Jeff Schewe. Perhaps you'd like to argue with him. I'm sure he'd be fascinated with your data.
--Bob

It does't matter who he is. If he knows what he is talking about then you are misrepresenting what he said.

I doubt that he ever said that the ACR histogram represents the unchangeable raw values from 0 through 16383. Just look at the display!

You can do the experiment with any of your own images and you will see for yourself. It only takes a couple of minutes. Trust but verify.

Anyone can do the same experiment with their own raw files.

There is no shame in being ignorant of the facts. But ignoring something that is staring you in the face just means that you are stubborn and unwilling to learn.

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Jan 14, 2019 10:37:01   #
Rich1939 Loc: Pike County Penna.
 
selmslie wrote:
It does't matter who he is. If he knows what he is talking about then you are misrepresenting what he said.

I doubt that he ever said that the ACR histogram represents the unchangeable raw values from 0 through 16383. Just look at the display!

You can do the experiment with any of your own images and you will see for yourself. It only takes a couple of minutes. Trust but verify.

Anyone can do the same experiment with their own raw files.

There is no shame in being ignorant of the facts. But ignoring something that is staring you in the face just means that you are stubborn and unwilling to learn.
It does't matter who he is. If he knows what he i... (show quote)


?? When I first open a RAW file in ACR and before any changes, what is it that the histogram is representing?

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Jan 14, 2019 10:45:56   #
selmslie Loc: Fernandina Beach, FL, USA
 
Rich1939 wrote:
?? When I first open a RAW file in ACR and before any changes, what is it that the histogram is representing?

Only a starting point with a small number of default adjustments.

If you turn on the highlight warnings you are probably seeing where the raw file values exceed the 8000 level, just as your camera's blinkies would.

If you move the exposure slider or the highlight recovery slider you can move the histogram while at the same time making the highlight warnings go away.

Now compare that to the RawDigger histograms which you cannot move at all.

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Jan 14, 2019 10:49:34   #
Rich1939 Loc: Pike County Penna.
 
selmslie wrote:
Only a starting point with a small number of default adjustments.

If you turn on the highlight warnings you are probably seeing where the raw file values exceed the 8000 level, just as your camera's blinkies would.

If you move the exposure slider or the highlight recovery slider you can move the histogram while at the same time making the highlight warnings go away.

Now compare that to the RawDigger histograms which you cannot move at all.


But my question was, what is it(histogram) reading before any adjustments are made.
It would make sense to have the histogram start with the raw information and then reflect changes made as processing continues.

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Jan 14, 2019 10:58:36   #
selmslie Loc: Fernandina Beach, FL, USA
 
Rich1939 wrote:
But my question was, what is it(histogram) reading before any adjustments are made

It is a representation of the initial state of the JPEG after the default adjustments are applied. That’s why it will change as you override those default adjustments.

If you look at the image presented in the RawDigger display, it is also a JPEG after some adjustments. That image tells us something about the potential for a decent result but only the histogram tells us what is actually in the raw file.

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Jan 14, 2019 11:04:01   #
Rich1939 Loc: Pike County Penna.
 
selmslie wrote:
It is a representation of the initial state of the JPEG after the default adjustments are applied. That’s why it will change as you override those default adjustments.

If you look at the image presented in the RawDigger display, it is also a JPEG after some adjustments. That image tells us something about the potential for a decent result but only the histogram tells us what is actually in the raw file.


I edited my response with this;
It would make sense to have the histogram start with the raw information and then reflect changes made as processing continues.

To that I'll add;
In camera jpegs will reflect user jpeg settings the ACR starting histogram does not What then does it represent other than the RAW data?

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Jan 14, 2019 11:23:58   #
selmslie Loc: Fernandina Beach, FL, USA
 
Rich1939 wrote:
I edited my response with this;
It would make sense to have the histogram start with the raw information and then reflect changes made as processing continues.

To that I'll add;
In camera jpegs will reflect user jpeg settings the ACR starting histogram does not What then does it represent other than the RAW data?

It depends on how you set up your raw editor.

For example, a raw editors might apply the camera's white balance setting to the initial display (the raw file doesn't have a white balance setting). It might also recover some of the highlight or shadow information for you to make the initial display a little better than the JPEG SOOC.

But in any case, the editor's histogram is from the JPEG being displayed, not from the raw file. If it were from the raw file, every image that is exposed ETTR (but not EBTR) would start with about a one stop gap to the right of the editor's histogram.

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Jan 14, 2019 11:35:35   #
rmalarz Loc: Tempe, Arizona
 
Rich, as you stated, the histogram, in ACR, is reading the RAW data. The only thing ACR uses from the RAW file is WB and the ISO metadata-per Jeff Schewe. Considering the source, that's something you can take to the bank.
--Bob
Rich1939 wrote:
?? When I first open a RAW file in ACR and before any changes, what is it that the histogram is representing?

Reply
Jan 14, 2019 11:37:22   #
Rich1939 Loc: Pike County Penna.
 
selmslie wrote:
It depends on how you set up your raw editor.

For example, a raw editors might apply the camera's white balance setting to the initial display (the raw file doesn't have a white balance setting). It might also recover some of the highlight or shadow information for you to make the initial display a little better than the JPEG SOOC.

But in any case, the editor's histogram is from the JPEG being displayed, not from the raw file. If it were from the raw file, every image that is exposed ETTR (but not EBTR) would start with about a one stop gap to the right of the editor's histogram.
It depends on how you set up your raw editor. br... (show quote)

Both the display image and the histogram are primarily representations of data stored in the raw file. They will also reflect user changes. It all starts with the RAW file.
In addition I can open any of my .nef files and remove any or all adjustments. That can't be done with a jpg

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Jan 14, 2019 11:38:49   #
selmslie Loc: Fernandina Beach, FL, USA
 
rmalarz wrote:
Rich, as you stated, the histogram, in ACR, is reading the RAW data. The only thing ACR uses from the RAW file is WB and the ISO metadata-per Jeff Schewe. Considering the source, that's something you can take to the bank.
--Bob

So how do you explain the lack of a gap on the right for an ETTR (not EBTR) image?

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Jan 14, 2019 11:44:14   #
selmslie Loc: Fernandina Beach, FL, USA
 
Rich1939 wrote:
Both the display image and the histogram are primarily representations of data stored in the raw file. They will also reflect user changes. It all starts with the RAW file.
In addition I can open any of my .nef files and remove any or all adjustments. That can't be done with a jpg

The JPEG you see in your editor is created on the fly, just like it is in your camera, based on the current adjustment settings.

You can’t view an image from a raw file without any adjustments.

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Jan 14, 2019 11:48:27   #
Rich1939 Loc: Pike County Penna.
 
selmslie wrote:
The JPEG you see in your editor is created on the fly, just like it is in your camera, based on the current adjustment settings.

You can’t view an image from a raw file without any adjustments.


The image I see on in my processor screen is created from the raw file. A.jpeg is a data file, not an image

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Jan 14, 2019 11:58:36   #
selmslie Loc: Fernandina Beach, FL, USA
 
Rich1939 wrote:
The image I see on in my processor screen is created from the raw file. A.jpeg is a data file, not an image

It has all of the characteristics of a JPEG including the 8-bit representation (unless you have a 10-bit display). This is the case even if you eventually export it as a 16-bit TIFF.

But I’ll ask again about the histogram, “Where’s the gap?”

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