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General / Re: Radiometric calibration using the "use sun sensor" option.
« on: March 13, 2026, 03:42:46 PM »
I can't find any technical document explain this process either...
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General / Multispectral Orthomosaic export
« on: August 20, 2025, 06:16:35 PM »
I am working with multispectral imagery from the DJI Mavic 3 Multispectral (M3M). I have created a reflectance-calibrated orthomosaic in Metashape using a calibration panel.
When I export the orthomosaic, the output is very dark, and some bands (particularly Red and Red Edge) appear almost completely black when viewed outside of Metashape.
Could you please clarify:
1.
What is the correct expression to use in Set Raster Transform so that each band (G, R, RE, NIR) is exported with appropriate brightness and contrast for visualization?
----For example, is this the recommended form for calibrated data in the 0–1 range?
----(Bx * BRIGHTNESS) * CONTRAST + 0.5 * (1 - CONTRAST)
2.
How should I determine the appropriate brightness and contrast factors for each band?
– Should they be based on histogram percentiles (e.g., 2–98%), or are there default/recommended values for multispectral exports?
My goal is not to change the radiometric values (I need those preserved for analysis), but to create exports that are also easier to visualize in external software.
thanks.
When I export the orthomosaic, the output is very dark, and some bands (particularly Red and Red Edge) appear almost completely black when viewed outside of Metashape.
Could you please clarify:
1.
What is the correct expression to use in Set Raster Transform so that each band (G, R, RE, NIR) is exported with appropriate brightness and contrast for visualization?
----For example, is this the recommended form for calibrated data in the 0–1 range?
----(Bx * BRIGHTNESS) * CONTRAST + 0.5 * (1 - CONTRAST)
2.
How should I determine the appropriate brightness and contrast factors for each band?
– Should they be based on histogram percentiles (e.g., 2–98%), or are there default/recommended values for multispectral exports?
My goal is not to change the radiometric values (I need those preserved for analysis), but to create exports that are also easier to visualize in external software.
thanks.
3
Camera Calibration / Re: Bright and Cloudy Dark Spots in Orthomosaic After Reflectance Calibration
« on: January 23, 2025, 06:54:19 PM »
Here are screenshots of the issues.
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Camera Calibration / Bright and Cloudy Dark Spots in Orthomosaic After Reflectance Calibration
« on: January 23, 2025, 06:48:43 PM »
Hello,
I am experiencing an issue with bright and cloudy dark spots appearing in my orthomosaic after processing. The problem seems to originate from reflectance calibration, as I notice similar brightness/darkness inconsistencies in the individual images immediately after calibration.
When I zoom into the orthomosaic, I can see that the shadowy areas appear as polygonal-shaped regions. I am skeptical that this issue is related to cloud cover, as all my other surveys have been conducted under a range of cloud conditions without any issues.
I am using a DJI Mavic 3M multispectral drone and a MicaSense reflectance panel. I follow the same workflow for all 20 surveys I’ve processed, but this issue is only appearing in three of them.
I manually Calibrate reflectance by placing the panel images in the separate image group (Note: The Mavic 3M has a sun sensor, but it fails to calibrate irradiance on about 1/3 of the images for every survey I’ve done. Enabling or disabling the sun sensor does not seem to affect this issue).
The same workflow works fine for other surveys, but for the three problematic ones, I see this issue persist despite consistent settings and processing steps.
I’ve attached screenshots of the shadowy polygons in a reply to this message
Does anyone have insight into what could be causing these bright and dark spots in the orthomosaic? I’d appreciate any suggestions or recommendations! Thanks!
I am experiencing an issue with bright and cloudy dark spots appearing in my orthomosaic after processing. The problem seems to originate from reflectance calibration, as I notice similar brightness/darkness inconsistencies in the individual images immediately after calibration.
When I zoom into the orthomosaic, I can see that the shadowy areas appear as polygonal-shaped regions. I am skeptical that this issue is related to cloud cover, as all my other surveys have been conducted under a range of cloud conditions without any issues.
I am using a DJI Mavic 3M multispectral drone and a MicaSense reflectance panel. I follow the same workflow for all 20 surveys I’ve processed, but this issue is only appearing in three of them.
I manually Calibrate reflectance by placing the panel images in the separate image group (Note: The Mavic 3M has a sun sensor, but it fails to calibrate irradiance on about 1/3 of the images for every survey I’ve done. Enabling or disabling the sun sensor does not seem to affect this issue).
The same workflow works fine for other surveys, but for the three problematic ones, I see this issue persist despite consistent settings and processing steps.
I’ve attached screenshots of the shadowy polygons in a reply to this message
Does anyone have insight into what could be causing these bright and dark spots in the orthomosaic? I’d appreciate any suggestions or recommendations! Thanks!
5
Camera Calibration / Re: Issue with Reflectance Calibration on DJI Mavic 3M Multispectral Images
« on: January 16, 2025, 01:23:14 AM »
Hello, thank you again for your help!
I’ve duplicated the reflectance panel image (e.g., loaded it into my workspace) two additional times, so now there are three instances of the same reflectance panel image. I applied the mask to all bands in all the images and manually added a reflectance panel photo to each of the three camera groups.
However, not all images and bands were calibrated successfully (see screenshot: "IncompleReflectanceCal.png"), even when the reflectance panel photo exists within the same camera group. The issue seems to occur mostly (or exclusively) with the RGB images (see screenshot #2: "rgb_not_cal.jpg").
Do you have any idea what might be causing this issue? Why are multiple camera groups automatically created—is it due to the large number of images in this survey? Additionally, can these camera groups be combined into a single group to simplify the calibration process?
Thank you again!
I’ve duplicated the reflectance panel image (e.g., loaded it into my workspace) two additional times, so now there are three instances of the same reflectance panel image. I applied the mask to all bands in all the images and manually added a reflectance panel photo to each of the three camera groups.
However, not all images and bands were calibrated successfully (see screenshot: "IncompleReflectanceCal.png"), even when the reflectance panel photo exists within the same camera group. The issue seems to occur mostly (or exclusively) with the RGB images (see screenshot #2: "rgb_not_cal.jpg").
Do you have any idea what might be causing this issue? Why are multiple camera groups automatically created—is it due to the large number of images in this survey? Additionally, can these camera groups be combined into a single group to simplify the calibration process?
Thank you again!
6
Camera Calibration / Re: Issue with Reflectance Calibration on DJI Mavic 3M Multispectral Images
« on: January 14, 2025, 10:16:30 PM »
Hello,
Thank you for your quick reply!
I’ve attached screenshots of the Calibration Reflectance dialog and the Camera Calibration dialog.
Note, that I do mask out the reflectance panel itself for each of the bands before running the reflectance calibration
I’ve enabled the Sun Sensor option, but, it failed on approximately 600 of the 3000 images. Additionally, only about 2500 of the 3000 images were successfully calibrated for reflectance. The resulting orthomosaic can also be seen in the screenshot.
Thank you
Thank you for your quick reply!
I’ve attached screenshots of the Calibration Reflectance dialog and the Camera Calibration dialog.
Note, that I do mask out the reflectance panel itself for each of the bands before running the reflectance calibration
I’ve enabled the Sun Sensor option, but, it failed on approximately 600 of the 3000 images. Additionally, only about 2500 of the 3000 images were successfully calibrated for reflectance. The resulting orthomosaic can also be seen in the screenshot.
Thank you
7
Camera Calibration / Issue with Reflectance Calibration on DJI Mavic 3M Multispectral Images
« on: January 13, 2025, 10:51:47 PM »Hi everyone,
I am encountering an issue with reflectance calibration in Metashape, and I would appreciate any insights or advice.
I am using a DJI Mavic 3 Multispectral drone along with a MicaSense calibration panel. I have followed the recommended steps for manual reflectance calibration sense the panel is not automatically detected.
This process worked perfectly for one of my surveys. However, when I tried to calibrate reflectance for subsequent surveys, only a portion of the images gets calibrated, while the rest remain uncalibrated.
As a result, the orthomosaic ends up with inconsistent colors, and the imagery is essentially unusable—colors are completely off, making it very difficult to interpret or analyze.
Has anyone else experienced this issue or know what might be causing it?
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