I was running a simple mapping flight test with Drone Deploy today on my M3E and noted some serious lens distortion on the Wide Camera on several of the images.  I uploaded the .DNG files to Lightroom Classic and Lightroom indicated that the internal lens distortion profile was applied.  The distortion is still there.  The distortion is present in the .jpg files as well.

Has anyone seen this issue in their work?  Is this a known issue or am I not doing something right?

May be easier to offer a comparison if you could post an example or two and point out your concern.

TonyPHX Posted at 6-14 15:03
May be easier to offer a comparison if you could post an example or two and point out your concern.

I tried in the original post but the attach feature didn't like the file size even after I down sampled the images.

Gizmo6 Posted at 6-14 15:27
I tried in the original post but the attach feature didn't like the file size even after I down sampled the images.

[view_image]

Hi,

yes the mavic3e has significant radial distorsion as seen in following where radial distorsion reaches 587 pixels in image corners.
However, if you correctly model these distorsions, you can have a good outcome....

I am attaching the screen capture of distorted image and related undistorted image (using relevant distorsion model) to sww thw difference..

You can use ExifTool to see the dewarping metadata of your camera. This would be DJI's dewarping parameters when this toggle is enabled. Never turn on dewarping when mapping/modeling.

PaulKofi Posted at 6-14 16:15
Hi,

yes the mavic3e has significant radial distorsion as seen in following where radial distorsion reaches 587 pixels in image corners.

Thank you.  The distortion is clearly visible in your before and after correction.  By modeling do you mean using software to process individual images or the resulting mosaic?  

Johnnokomis Posted at 6-14 17:02
You can use ExifTool to see the dewarping metadata of your camera. This would be DJI's dewarping parameters when this toggle is enabled. Never turn on dewarping when mapping/modeling.

Thank you for that insight.  I trust that once I have obtained the dewarp metadata for my camera I can feed that into Lightroom as a distortion profile?

Gizmo6 Posted at 6-14 17:18
Thank you for that insight.  I trust that once I have obtained the dewarp metadata for my camera I can feed that into Lightroom as a distortion profile?

I honestly don't know if this is a camera lens specific value, or a generic value that DJI gives to all M3E's. I'd be a shame if DJI claims the accuracy that they do while calibrating every camera the same. I've checked 3 different M3E's and though I don't remember the values on them I know they all shared the same June 8, 2022 calibration date. When you look at yours please share what values you find.

Gizmo6 Posted at 6-14 17:11
Thank you.  The distortion is clearly visible in your before and after correction.  By modeling do you mean using software to process individual images or the resulting mosaic?

Exactly using a photogrammetric package, you can then align and optimize your imagery including defining the internal camera parameters (focal, principal point and distorsion). Then you  can use these to create undistorted images  if you want to.... Also the resulting products (DEM, Ortho,...) will take parameters into consideration to eliminate distorsion.....

Internal parameters or camera  intrinsics are equivalent to Dewarp parameters mentioned by John. But it is better with good shooting geometry to let the software package do the intrinsics determination (self calibration) and so to turn Dewarp off on the M3E...

Johnnokomis Posted at 6-14 18:27
I honestly don't know if this is a camera lens specific value, or a generic value that DJI gives to all M3E's. I'd be a shame if DJI claims the accuracy that they do while calibrating every camera the same. I've checked 3 different M3E's and though I don't remember the values on them I know they all shared the same June 8, 2022 calibration date. When you look at yours please share what values you find.

Hello John,

here the dewarp parameters from my camera:

DewarpData                      : 2022-06-08;3713.290000000000,3713.290000000000,7.020000000000,-8.720000000000,-0.112575240000,0.014874430000,-0.000085720000,0.000000100000,-0.027064110000
They seem to be the same...I would not trust these as different cameras should have different parameters....

Johnnokomis Posted at 6-14 18:27
I honestly don't know if this is a camera lens specific value, or a generic value that DJI gives to all M3E's. I'd be a shame if DJI claims the accuracy that they do while calibrating every camera the same. I've checked 3 different M3E's and though I don't remember the values on them I know they all shared the same June 8, 2022 calibration date. When you look at yours please share what values you find.

I suspect that DJI is using the same dewarp values for all of their 20MP lens.  I know that Nikon does this for their production lenses via distortion profiles that we download and install in a given camera (e.g D850, Z7, etc.).  This may not be the case with DJI lenses.

I will share the values from my M3E cam once I have a Exif viewer than can expose them.

  

PaulKofi Posted at 6-15 04:15
Exactly using a photogrammetric package, you can then align and optimize your imagery including defining the internal camera parameters (focal, principal point and distorsion). Then you  can use these to create undistorted images  if you want to.... Also the resulting products (DEM, Ortho,...) will take parameters into consideration to eliminate distorsion.....

Internal parameters or camera  intrinsics are equivalent to Dewarp parameters mentioned by John. But it is better with good shooting geometry to let the software package do the intrinsics determination (self calibration) and so to turn Dewarp off on the M3E...

I believe that 3Dsurvey photogrammetric processing software can do what you are suggesting.

Most my clients use their own processing workflows, so I only did a short trial with 3Dsurvey and the results looked usable.

PaulKofi Posted at 6-15 04:23
Hello John,

here the dewarp parameters from my camera:

Ah, this makes sense in a way. Dewarp is just for photography shots when consistency isn't needed. It would be nice if DJI would allow us to save our own dewarp profiles internally to replace their one size fits all calibration. Lightroom has several DJI lens correction profiles but not for any drones released in the past 4 or 5 years. Lightroom also claims that a built in lens correction has been applied to images when clearly it hasn't.

PaulKofi Posted at 6-15 04:15
Exactly using a photogrammetric package, you can then align and optimize your imagery including defining the internal camera parameters (focal, principal point and distorsion). Then you  can use these to create undistorted images  if you want to.... Also the resulting products (DEM, Ortho,...) will take parameters into consideration to eliminate distorsion.....

Internal parameters or camera  intrinsics are equivalent to Dewarp parameters mentioned by John. But it is better with good shooting geometry to let the software package do the intrinsics determination (self calibration) and so to turn Dewarp off on the M3E...

Right, at least for Metashape, a new calibration is preformed everytime an alignment is done. I've used the checkerboard process to calibrate mine and have that saved as an .XML for future yes. This processed worked very well for the Phantom 4 but these values don't seem to hold as consistently with the M3E.

I found the lens distortion correction profile on Lensfun, and then wrote this little bash script to apply the correction to photos in a directory:

This is a bash script for running in linux. You could ask ChatGPT to adjust it to a windows or Mac environment.

for f in *.JPG; do
  convert "$f" \
    -distort barrel \
    '-0.0167982 0.00725109 -0.03131' \
    "output_${f}"
done

You need to install ImageMagick https://imagemagick.org/index.php, and you can find the lensfun profile here: https://github.com/lensfun/lensfun/blob/master/data/db/actioncams.xml#L292


More information on how I figured this out here:https://legacy.imagemagick.org/Usage/lens/

aerbits Posted at 9-18 14:49
I found the lens distortion correction profile on Lensfun, and then wrote this little bash script to apply the correction to photos in a directory:

This is a bash script for running in linux. You could ask ChatGPT to adjust it to a windows or Mac environment.

Thank you for taking the time to do this...

PaulKofi Posted at 2023-6-14 16:15
Hi,

yes the mavic3e has significant radial distorsion as seen in following where radial distorsion reaches 587 pixels in image corners.
[Image]

Hi
I did this progress including align images, add ground control points , reducing gradual selection then I attempt to export undistorted images but my outputs are not similar to yours!
Can you explain what you do exactly?