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Author Topic: Manually introducing Camera Model  (Read 3463 times)

ArnauCM

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Manually introducing Camera Model
« on: April 30, 2018, 10:16:36 PM »
Hi!

We have been flying with a UAV over a forest plot. After extracting the frames with Photoshop I always lose the camera info, so when I try to calibrate it, it appears as "unknown camera". Is there any way in Agisoft to manually introduce Camera model so that the software can make the proper lens correction, etc.?

Thanks a lot!

SAV

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Re: Manually introducing Camera Model
« Reply #1 on: May 01, 2018, 08:27:00 AM »
Hi ArnauCM,

It's under TOOLS > CAMERA CALIBRATION

Enter or load your camera lens correction values in the INITIAL tab and check FIX CALIBRATION in order to protect it from recalculation (only do this if you have precise calibration data available).

All the best.

Regards,
SAV

ArnauCM

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Re: Manually introducing Camera Model
« Reply #2 on: May 01, 2018, 05:14:50 PM »
Hi SAV,

Thanks for your reply. So that's all Agisoft takes into account? Just Focal length and type of frame? Because there is nothing else I can add as input.

SAV

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Re: Manually introducing Camera Model
« Reply #3 on: May 02, 2018, 07:27:25 AM »
Hi ArnauCM,

You have to choose Type: PRECALIBRATED instead of Auto.

Then you can enter:
f: Focal length measured in pixels
cx, cy: Principal point coordinates
b1, b2: Affinity and Skew (non-orthogonality) transformation coefficients.
k1, k2, k3, k4: Radial distortion coefficients.
p1, p2, p3, p4: Tangential distortion coefficients.


All the best.

Regards,
SAV

Alexey Pasumansky

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Re: Manually introducing Camera Model
« Reply #4 on: May 03, 2018, 02:45:45 PM »
Hello ArnauCM,

If you mean just the loss of EXIF information, then you need only to input focal length and sensor pixel size (both in mm) values to the Camera Calibration dialog - these values would be used to estimate the Initial values for autocalibration procedure.

Be careful, however, if you are working with the variable focal length or with different cameras - if the EXIF data is stripped, then PhotoScan would likely put all the images of the same resolution to the same calibration group, which would mean incorrect estimation of the calibration parameters, if the focal length differs greatly during the image acquisition.
It is necessary to split the images to the calibration groups (in the Camera Calibration dialog) according to the different camera model, image resolution, focal length, sensor pixel size.
Best regards,
Alexey Pasumansky,
Agisoft LLC