Help wanted in interpreting K-3 Mark III exif entries

**tduell** · 06-09-2021, 02:44 AM

I'm attempting to update dcrawps to be able to handle the K-3 Mark III pixelshift images, and need some assistance in understanding an exif entry for a PS file from the camera.
What do the entries in the following mean? 'Active Area : 34 26 4194 6250'
Is one of these entries the left margin?

Cheers,
Terry

**ProfessorBuzz** · 06-09-2021, 05:04 AM

If I recall correctly, the sensor has a series of reference pixels (some black masked) around the edges, and these can be used for referencing the dark level.

Paul the Sunman · 06-09-2021, 05:11 AM

The K3iii sensor is 4128 x 6192 pixels, so those upper values don't even quite fit on it, unless they are extended to include sensor shift for SR or composition adjustment.

stevebrot · 06-09-2021, 08:33 AM

ActiveArea is part of standard EXIF and is written in files from my K-3 as well. I am not sure, but suspect that it represents coordinates for opposing corners of the sensor. Google may be our friend here.

Steve

**kwb** · 06-09-2021, 09:33 AM

See EXIF specifications. https://www.adobe.com/content/dam/acom/en/products/photoshop/pdfs/dng_spec_1.4.0.0.pdf

ActiveArea defines the pixels that receive light (as opposed to masked pixels used for something else). Though I don't have K-3III (yet), if I use your example of

Active Area: 34 26 4194 6250
the top left corner of that area is (Y, X)=(34, 26) but note that the origin is (0,0).
I interpret the spec to mean that the bottom right corner is (4193, 6249) in K-3 III's case (i.e. the active area is 4160x6224).

This is larger than the picture size in color filter array sensors (e.g. Bayer). If you don't have these "extra" pixels, color interpolation won't work at the edges.

Look at Default Crop Size and Default Crop Origin to see the actual areas corresponding to the final images. Unlike ActiveArea, the order is X before Y.

**tduell** · 06-09-2021, 04:51 PM

Originally posted by kwb

See EXIF specifications. https://www.adobe.com/content/dam/acom/en/products/photoshop/pdfs/dng_spec_1.4.0.0.pdf

ActiveArea defines the pixels that receive light (as opposed to masked pixels used for something else). Though I don't have K-3III (yet), if I use your example of

Active Area: 34 26 4194 6250
the top left corner of that area is (Y, X)=(34, 26) but note that the origin is (0,0).
I interpret the spec to mean that the bottom right corner is (4193, 6249) in K-3 III's case (i.e. the active area is 4160x6224).

This is larger than the picture size in color filter array sensors (e.g. Bayer). If you don't have these "extra" pixels, color interpolation won't work at the edges.

Look at Default Crop Size and Default Crop Origin to see the actual areas corresponding to the final images. Unlike ActiveArea, the order is X before Y.

Thanks for that info.
I did quite a bit of searching but obviously didn't choose my target well enough, so ended up here where we always get help.
From the above, and the reference spec, I understand now that the left margin is 26.
Things have moved on since my original post, and I may not have to nut out changes to dcrawps for the K-3 Mark III, as the original author of dcrawps has offered to have a look at updating the code.

Thanks to all who tried to help.

Cheers,
Terry

**jbinpg** · 06-09-2021, 05:54 PM

Thanks, Terry, for encouraging the dcrawps author to update his code. Please post back here when and where it is available for download.

Jack

06-09-2021, 02:44 AM	#1
tduell Loyal Site Supporter Join Date: May 2015 Location: Melbourne Posts: 1,514	Help wanted in interpreting K-3 Mark III exif entries I'm attempting to update dcrawps to be able to handle the K-3 Mark III pixelshift images, and need some assistance in understanding an exif entry for a PS file from the camera. What do the entries in the following mean? 'Active Area : 34 26 4194 6250' Is one of these entries the left margin? Cheers, Terry

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06-09-2021, 05:04 AM	#2
ProfessorBuzz Loyal Site Supporter Join Date: Feb 2018 Posts: 1,903	If I recall correctly, the sensor has a series of reference pixels (some black masked) around the edges, and these can be used for referencing the dark level.

06-09-2021, 05:11 AM	#3
Paul the Sunman Pentaxian Join Date: Aug 2011 Location: Melbourne Photos: Gallery Posts: 4,843	The K3iii sensor is 4128 x 6192 pixels, so those upper values don't even quite fit on it, unless they are extended to include sensor shift for SR or composition adjustment.

06-09-2021, 08:33 AM	#4
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	ActiveArea is part of standard EXIF and is written in files from my K-3 as well. I am not sure, but suspect that it represents coordinates for opposing corners of the sensor. Google may be our friend here. Steve

06-09-2021, 09:33 AM	#5
kwb Site Supporter Join Date: Mar 2015 Location: Pacific North West Photos: Gallery \| Albums Posts: 1,223	See EXIF specifications. https://www.adobe.com/content/dam/acom/en/products/photoshop/pdfs/dng_spec_1.4.0.0.pdf ActiveArea defines the pixels that receive light (as opposed to masked pixels used for something else). Though I don't have K-3III (yet), if I use your example of Active Area: 34 26 4194 6250 the top left corner of that area is (Y, X)=(34, 26) but note that the origin is (0,0). I interpret the spec to mean that the bottom right corner is (4193, 6249) in K-3 III's case (i.e. the active area is 4160x6224). This is larger than the picture size in color filter array sensors (e.g. Bayer). If you don't have these "extra" pixels, color interpolation won't work at the edges. Look at Default Crop Size and Default Crop Origin to see the actual areas corresponding to the final images. Unlike ActiveArea, the order is X before Y.

06-09-2021, 04:51 PM	#6
tduell Loyal Site Supporter Join Date: May 2015 Location: Melbourne Posts: 1,514 Original Poster	Originally posted by kwb See EXIF specifications. https://www.adobe.com/content/dam/acom/en/products/photoshop/pdfs/dng_spec_1.4.0.0.pdf ActiveArea defines the pixels that receive light (as opposed to masked pixels used for something else). Though I don't have K-3III (yet), if I use your example of Active Area: 34 26 4194 6250 the top left corner of that area is (Y, X)=(34, 26) but note that the origin is (0,0). I interpret the spec to mean that the bottom right corner is (4193, 6249) in K-3 III's case (i.e. the active area is 4160x6224). This is larger than the picture size in color filter array sensors (e.g. Bayer). If you don't have these "extra" pixels, color interpolation won't work at the edges. Look at Default Crop Size and Default Crop Origin to see the actual areas corresponding to the final images. Unlike ActiveArea, the order is X before Y. Thanks for that info. I did quite a bit of searching but obviously didn't choose my target well enough, so ended up here where we always get help. From the above, and the reference spec, I understand now that the left margin is 26. Things have moved on since my original post, and I may not have to nut out changes to dcrawps for the K-3 Mark III, as the original author of dcrawps has offered to have a look at updating the code. Thanks to all who tried to help. Cheers, Terry

06-09-2021, 05:54 PM	#7
jbinpg Site Supporter Join Date: Mar 2008 Location: Prince George, BC Photos: Gallery \| Albums Posts: 3,546	Thanks, Terry, for encouraging the dcrawps author to update his code. Please post back here when and where it is available for download. Jack