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Affinity Photo Altering Canon EXIF ISO Values

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When editing image files from a Canon camera in Affinity Photo, if the ISO value isn’t in whole stops (I.E. 800, 1600, 3200, 6400), the ISO value in the EXIF metadata is altered slightly when it’s exported, meaning it differs to what Canon set the metadata as.

The camera is using Auto ISO, therefore the camera automatically determines ISO.

This issue occurs both with a .CR2 raw file opened directly in Affinity Photo and also with a .TIF file exported from Canon DPP 4 and then opened in Affinity Photo.

 

In the below image file, when the image is exported from Affinity Photo, Affinity Photo changes the EXIF ISO value from ISO 1000 to ISO 1037.

001.thumb.png.728ceb9c19290fa59a5f332536ff6870.png

002.thumb.png.b54eaf165f1a8e52bc3fecfeb9d165c9.png

 

In the below image file, when the image is exported from Affinity Photo, Affinity Photo changes the EXIF ISO value from ISO 2000 to ISO 2075.

003.thumb.png.660583e46bbff0ea1e5540348e89a4a7.png

 

In the below image file, when the image is exported from Affinity Photo, Affinity Photo changes the EXIF ISO value from ISO 2500 to ISO 2468.

004.thumb.png.5ebb3b9cdb83db51d9c446874283f133.png

 

In the below image file, when the image is exported from Affinity Photo, Affinity Photo changes the EXIF ISO value from ISO 4000 to ISO 4150.

005.thumb.png.d3431255d864ca7554acc023470d0b79.png

 

In the below image file, when the image is exported from Affinity Photo, Affinity Photo changes the EXIF ISO value from ISO 5000 to ISO 4935.

006.thumb.png.8a101b406e7623b7c57801338433deff.png

 

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On 9/9/2019 at 3:55 PM, Chris B said:

We could really do with the files—would you mind uploading them to this private Dropbox folder? Thanks! 

I've uploaded a zip file—which also contains more info.

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@- S -

What tool did you use to extract the EXIF data to a nicely formated txt file? It looks neat :)


"Men are like sheep, of which a flock is more easily driven than a single one."

"Experienced vector artists and infographic designers will find a noticeable lack of the more advanced tools found in Illustrator CC." (source)

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3 hours ago, Jowday said:

@- S -

What tool did you use to extract the EXIF data to a nicely formated txt file? It looks neat :)

If you mean the first two screenshots, that’s just command-line tool ExifTool being run from Windows PowerShell.  It’s possible to do exactly the same with PowerShell or PowerShell ISE built in to Windows.  However, PowerShell ISE is no longer in active development and is being replaced with Visual Studio Code (VS Code) combined with the PowerShell extension for VS Code—which are both free, open-source and cross platform (Mac, Windows & Linux).  This is what I’m using in the screenshots.

If you mean the other screenshots with the comparisons, VS Code has the built-in ability to compare two files, I’m just using it to compare the metadata outputs from ExifTool.
 

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4 hours ago, - S - said:

If you mean the first two screenshots, that’s just command-line tool ExifTool being run from Windows PowerShell.  It’s possible to do exactly the same with PowerShell or PowerShell ISE built in to Windows.  However, PowerShell ISE is no longer in active development and is being replaced with Visual Studio Code (VS Code) combined with the PowerShell extension for VS Code—which are both free, open-source and cross platform (Mac, Windows & Linux).  This is what I’m using in the screenshots.

@- S - Thank you for the detailed answer and links! :235_bee:


"Men are like sheep, of which a flock is more easily driven than a single one."

"Experienced vector artists and infographic designers will find a noticeable lack of the more advanced tools found in Illustrator CC." (source)

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Hey - S -,

We are showing the true ISO numbers. This may be a 'Canon thing' as we've checked with RW2, ARW and ORF files which don't seem to be doing the same thing. We also thought it may be a result of using automatic ISO but this doesn't appear to be the case.

Our in-house photographer always sets the ISO manually and is seeing the same thing as you with his Canon files but not for the other files mentioned above.

 

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On 9/12/2019 at 2:00 PM, Chris B said:

We are showing the true ISO numbers. This may be a 'Canon thing' as we've checked with RW2, ARW and ORF files which don't seem to be doing the same thing. We also thought it may be a result of using automatic ISO but this doesn't appear to be the case.

Our in-house photographer always sets the ISO manually and is seeing the same thing as you with his Canon files but not for the other files mentioned above.

While this only affects Canon files, the issue lies in how Affinity Photo is reading the metadata from the file.

Instead of reading the ISO value from the EXIF metadata field, Affinity Photo is ignoring that EXIF field and instead using a calculated ISO value from a different field.  When the file is then saved, Affinity Photo overwrites the EXIF metadata field with this calculated value—which it shouldn’t be doing, as that field already contains the correct value for that tag.

Below is the ISO metadata from different camera raw files as displayed by ExifTool and the metadata values being used by Affinity Photo.

Canon 80D (CR2 raw file)

[ExifIFD]       ISO                             : 2500
[ExifIFD]       Recommended Exposure Index      : 2500
[Canon]         Auto ISO                        : 100
[Canon]         Base ISO                        : 2468
[Canon]         ISO                             : 2468
[Composite]     ISO                             : 2468

Affinity Photo is reading the ISO value from the following metadata field:
[Composite] ISO (This isn’t a tag written by Canon, this is a made up tag)

Canon DPP 4 reads the ISO value from the following metadata field:
[ExifIFD] ISO

Windows File Explorer and Windows Photos app read the ISO value from the following metadata field:
[ExifIFD] Recommended Exposure Index

Canon 80D (TIF file exported from Canon DPP 4)

[ExifIFD]       ISO                             : 2500
[ExifIFD]       Recommended Exposure Index      : 2500
[Canon]         Auto ISO                        : 100
[Canon]         Base ISO                        : 2468
[Composite]     ISO                             : 2468

Affinity Photo is reading the ISO value from the following metadata field:
[Composite] ISO (This isn’t a tag written by Canon, this is a made up tag)

Canon DPP 4 reads the ISO value from the following metadata field:
[ExifIFD] ISO

Windows File Explorer and Windows Photos app read the ISO value from the following metadata field:
[ExifIFD] ISO

Canon 20D (CR2 raw file from 2004)

[ExifIFD]       ISO                             : 800
[Canon]         Auto ISO                        : 100
[Canon]         Base ISO                        : 800
[Composite]     ISO                             : 800

Affinity Photo is reading the ISO value from the following metadata field:
[Composite] ISO (This isn’t a tag written by Canon, this is a made up tag)

Canon DPP 4 reads the ISO value from the following metadata field:
[ExifIFD] ISO

Windows File Explorer and Windows Photos app read the ISO value from the following metadata field:
[ExifIFD] ISO

Fujifilm X-T2 (RAF raw file)

[ExifIFD]       ISO                             : 2000

Affinity Photo is reading the ISO value from the following metadata field:
[ExifIFD] ISO

Nikon D5 (NEF raw file)

[ExifIFD]       ISO                             : 2200
[Nikon]         ISO                             : 2263
[Nikon]         ISO2                            : 504

Affinity Photo is reading the ISO value from the following metadata field:
[ExifIFD] ISO

Nikon D500  (NEF raw file) (Adobe ACR 9.5.1)

[XMP-exif]      ISO                             : 2000
[ExifIFD]       ISO                             : 2000
[Nikon]         ISO                             : 2016
[Nikon]         ISO2                            : 12800

Affinity Photo is reading the ISO value from the following metadata field:
[ExifIFD] ISO

Olympus E-M1 Mark II (ORF raw file)

[ExifIFD]       ISO                             : 4000

Affinity Photo is reading the ISO value from the following metadata field:
[ExifIFD] ISO

Panasonic G9 (RW2 raw file)

[IFD0]          ISO                             : 2000
[ExifIFD]       ISO                             : 2000
[ExifIFD]       Standard Output Sensitivity     : 2000

Affinity Photo is reading the ISO value from the following metadata field:
[ExifIFD] ISO or [IFD0] ISO

Sony A6500 (ARW raw file)

[ExifIFD]       ISO                             : 2000
[ExifIFD]       Recommended Exposure Index      : 2000
[Sony]          Sony ISO                        : 1971
[Sony]          Base ISO                        : 100
[Sony]          Stops Above Base ISO            : 4.3

Affinity Photo is reading the ISO value from the following metadata field:
[ExifIFD] ISO

----

Affinity Photo is either using ExifTool behind the scenes and using the [Composite] ISO tag to generate the ISO value for Canon files, or it’s using the same logic that ExifTool uses to generate the [Composite] ISO tag.

However, the [Composite] ISO tag is derived from [Canon] Base ISO multiplied by [Canon] Auto ISO divided by 100.  This isn’t a tag written by Canon, this is a tag made up by ExifTool.

So, although the issue only affects how Affinity Photo handles Canon files, the issue still remains:  For Canon files, if the file has a valid [ExifIFD] ISO metadata field like the above files do, then Affinity Photo should be reading the ISO value from this metadata field.

Instead, it’s using a different metadata field; then when saving a file in Affinity Photo, Affinity Photo overwrites the [ExifIFD] ISO metadata value in the file with a different ISO value. Affinity Photo shouldn’t be altering this EXIF ISO value—the EXIF ISO value should remain as written by the camera.

 

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Hey - S -,

First of all—thank you for putting together such a comprehensive case. You must have spent some time on this and I am grateful.

Secondly—I've been speaking with the developers about all this and we have agreed that at some point in the future, there are some improvements we would like to make so this will be revisited. 

 

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1 hour ago, Chris B said:

Hey - S -,

First of all—thank you for putting together such a comprehensive case. You must have spent some time on this and I am grateful.

Secondly—I've been speaking with the developers about all this and we have agreed that at some point in the future, there are some improvements we would like to make so this will be revisited. 

Thanks.

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