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Author Topic: Different Focal Length and Different Rotation of Camera - FORBIDDEN  (Read 2341 times)

JohnyJoe

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Hello, i have been using some old version of agisoft metashape, now im using some newer but still older version (than the current one is). Its 1.5.5.

With this "newer but still old version" i got new error messages pop up here there, these didnt pop up EVER in previous versions.



They say:

Warning! The following problems can lead to suboptimal results:

- Images with variable zoom are added to the project. It is strongly recommended to avoid zooming as much as possible.

Happens when i upload images with "zoom" (or different Focal lenght in other words).

I have ALWAYS done this and never had this warning pop up before... DOes using different Focal Lenght ("zoom") really negativelly affect the final quality of the scan...? I have never noticed that...? IS that true? Or is that true only with never versions of metashape and older could handle it and newer give worse results? Or is it in all photogrammetry software that using different focal length leads to bad results...? I would swear i did some tests with this back in 2015 (or whatever) when i started with 3D scanning and never saw bad results...?

Is it worse? How much worse is it...? Zoom is sometimes necessary i feel... Should i really avoid it like the plague?



And another one:

Warning! The following problems can lead to suboptimal results:

- Images with different orientation are added to the project. It is strongly recommended to disable auto rotation in the camera or photo processing software.


Again...? Does different rotation matter? (in this example i scanned some leaf and few photos had the same leaf, the same side of the leaf, just aprx. 90 degree rotated...

I have dont this before i think and no problem. No it gives me this warning and also the point cloud looks weird... (like wrong, "normals" flipped).



So how is?

    Is using different Focal length really THAT BAD? Should i avoid it at all cost...? (any pictures of tests for this...?)

    Is using different rotation (mainly switching holding the camera verticaly or horizonatally; but even rotations like 30% only for example)... Is this also BAD...? How MUCH bad... should be avoided at ALL COSTS...?


(camera i use: Nikon D3100)

rossnixon

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Re: Different Focal Length and Different Rotation of Camera - FORBIDDEN
« Reply #1 on: June 25, 2020, 01:54:00 PM »
I haven't noticed any problem with slightly different focal lengths. A mix of 24, 25, 26mm focal lengths has worked fine for me. It may depend how detailed and precise the result needs to be.

Alexey Pasumansky

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Re: Different Focal Length and Different Rotation of Camera - FORBIDDEN
« Reply #2 on: June 25, 2020, 11:54:32 PM »
Hello JohnyJoe,

The warning messages have been introduced in the version 1.5, unless I am mistaken. But the internal behavior is the same: the camera calibration groups will be automatically split according to the EXIF information such as focal length, camera model, pixel size.
In general the use of zoom-lens is not bad, but it could be worse, if you are using "zoom" intensively moving it back and forth. EXIF data wouldn't resolve minimal difference (like 0.1mm), but for the autocalibration procedure it may be a big difference.

As for the autorotation message, it appears when the images are captured with the same camera and lens, but the some of the images are 90 degrees rotated. For example, images 4000x3000 pixels and 3000x4000 pixels will be split into different groups, as they cannot be calibrated in the same group. That's why it is recommended to disable automatic rotation of the images in the camera settings.
Best regards,
Alexey Pasumansky,
Agisoft LLC

James

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Re: Different Focal Length and Different Rotation of Camera - FORBIDDEN
« Reply #3 on: June 26, 2020, 02:20:05 PM »
Not contradicting anything that Alexey said, and this may be out of date, but assuming you do have "auto-rotation" disabled in the camera I believe that it is still generally a good thing to have images taken in both landscape and portrait orientation, so long as those images all have the same pixel dimensions, enabling them to be treated together in the same calibration group.

the mix of portrait and landscape orientated photos [...] is generally a good advise for camera calibration

But regardless, if you get good results doing what you are doing, then the benefits of going out of your way to do this are probably very small.