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Author Topic: Which values does "Pixel size" in "Camera type: Frame" expect?  (Read 3137 times)

rowild

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Which values does "Pixel size" in "Camera type: Frame" expect?
« on: December 27, 2023, 02:21:18 AM »
I do not understand which values I am supposed to enter in the "Pixel Size" field, which appears when the "Frame" camera is chosen. The screenshot shows that I currently use 1920x1012 which is the (edited) output of a video of a DJI Mavic 3 camera (which is a frame camera, right?). (The specs of that drone camera can be found here: https://www.dji.com/at/mavic-3/specs)

I have a feeling that I am misunderstanding that input field... Any clarification would be most welcome! Thank you!

tazzo

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Re: Which values does "Pixel size" in "Camera type: Frame" expect?
« Reply #1 on: December 27, 2023, 02:23:29 AM »
it's the size of a single pixel on the sensor (usually much less than a millimeter).
All these info are already in the metadata of the pictures, why you need them?

rowild

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Re: Which values does "Pixel size" in "Camera type: Frame" expect?
« Reply #2 on: December 27, 2023, 02:36:14 AM »
Thank you for the quick answer! - there is  o such meta data in my images, because i sent the original video through Davinci Resolve and then through Blender, the latter creating the images from the video.
Just to get an idea: what would such a number look like? You say "less than a mm", but the software requires px values....

tazzo

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Re: Which values does "Pixel size" in "Camera type: Frame" expect?
« Reply #3 on: December 27, 2023, 03:05:27 AM »
If you modified the image it's a mess to calculate it. Load an unmodified image and copy values from there, it's the safest path if the image was not resized.

rowild

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Re: Which values does "Pixel size" in "Camera type: Frame" expect?
« Reply #4 on: December 27, 2023, 09:40:27 AM »
I just use Metashape's Video importer and let it extract the images from an oiginal. But there is still no info about the "Pixel Size". See screenshot.

(BTW: I cannot always use the original video, because it is shot in D-Log. I have to edit it first.)

But again: The input fields require a px value – you mention a value in mm-unit. How does that go together? Could you please post an image of what such a value could look like? Thank you!
« Last Edit: December 27, 2023, 10:06:24 AM by rowild »

tazzo

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Re: Which values does "Pixel size" in "Camera type: Frame" expect?
« Reply #5 on: December 27, 2023, 03:00:55 PM »
why px value? it's width x height in millimeters. What fields are you referring to?

rowild

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Re: Which values does "Pixel size" in "Camera type: Frame" expect?
« Reply #6 on: December 27, 2023, 03:22:31 PM »
You are totally right when you ask "Why px value?" - there is clearly a "(mm)" next to "Pixel Size"! I do need new glasses, as it seems. Or better even new eyes!  :-[

Anyway, my original material does not provide any such value. How can I define it?
(As mentioned above the footage is from a DJI Mavic 3 drone (camera specs in the link above). )

tazzo

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Re: Which values does "Pixel size" in "Camera type: Frame" expect?
« Reply #7 on: December 27, 2023, 04:11:27 PM »
try to take a picture with the drone at the same resolution of the video, load it in metashape, and copy data from there

rowild

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Re: Which values does "Pixel size" in "Camera type: Frame" expect?
« Reply #8 on: December 27, 2023, 04:12:38 PM »
Good idea! I'll do that!

Thank you!  :D

rowild

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Re: Which values does "Pixel size" in "Camera type: Frame" expect?
« Reply #9 on: December 27, 2023, 08:27:28 PM »
I found a discussion on the DJI forums about the pixel size of the mavic pro:

https://forum.dji.com/forum.php?mod=viewthread&tid=264807&page=1#pid2741845

3.33nm it is, they say. That should be 0.00000333 mm.

Would that be the correct number to enter in said input fields?
Do things like zoom (which I do not use in my current case) influence pixel size generallly?

tazzo

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Re: Which values does "Pixel size" in "Camera type: Frame" expect?
« Reply #10 on: December 27, 2023, 09:01:49 PM »
it's not 3.33nm (nanometers) for sure, maybe are 3.33um (micrometers). Pixel size is lens-independent. If you have multiple sensors be sure to take data from the correct one.
« Last Edit: December 27, 2023, 09:04:14 PM by tazzo »

rowild

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Re: Which values does "Pixel size" in "Camera type: Frame" expect?
« Reply #11 on: December 27, 2023, 09:27:08 PM »
Thank you again! I will try with 0.00333 then  ;D

tazzo

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Re: Which values does "Pixel size" in "Camera type: Frame" expect?
« Reply #12 on: December 27, 2023, 09:28:54 PM »
make more sense.. if pixels are squared you have to put the value in both width and height.
Be very careful when you enter other fields because 4K are around 8MP and your sensor is 20MP.. so you may need to account for any different field of view
« Last Edit: December 27, 2023, 09:31:16 PM by tazzo »

rowild

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Re: Which values does "Pixel size" in "Camera type: Frame" expect?
« Reply #13 on: December 27, 2023, 09:31:31 PM »
I let you know. I now need to check on your new statement "if pixels are squared"...

tazzo

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Re: Which values does "Pixel size" in "Camera type: Frame" expect?
« Reply #14 on: December 27, 2023, 09:33:32 PM »
if your drone is using the IMX272 then are squared (almost all camera sensors have squared pixels)