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Photogrammetry with 3d camera?


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#1 tosvus

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Posted 28 September 2016 - 04:50 AM

Hi, 

 

I am wondering if there is any benefit in having my camera capture two images at once, using something like the Kula deeper 3d lens attachment for dslr cameras. It will basically squeeze two images side by side into one picture. Of course, I would still like to follow the normal process of photographing the object from multiple angles, but just wondering if the stereoscopic images will be possible to make more accurate models (or use fewer shots from various angles).

 

Any feedback is greatly appreciated!



#2 Carla Schroer

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Posted 28 September 2016 - 06:09 AM

For photogrammetry software to create the best possible result (high precision with low uncertainty data) you need to move the camera between photos.  The recommended amount is 1/3 of the field of view (creating a 2/3 overlap).  The Kula system might be fine for doing individual "stereo" photos, and it looks like it can do stereo video as well. These could be viewed in various VR systems. However, it would absolutely not be recommended for a proper photogrammetric capture sequence.  It would most likely make your data worse.

 

We have some basic guidance for photogrammetric capture on our website here: http://culturalherit...ammetry/#how_to

 

We are working on a "Guide to Photogrammetric Image Capture" which will have a lot more detail, along with graphics and photos.  We expect to have it out before the end of the year.  it will be a free guide available under a Creative Commons license.

 

Carla



#3 tosvus

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Posted 29 September 2016 - 02:55 AM

For photogrammetry software to create the best possible result (high precision with low uncertainty data) you need to move the camera between photos.  The recommended amount is 1/3 of the field of view (creating a 2/3 overlap).  The Kula system might be fine for doing individual "stereo" photos, and it looks like it can do stereo video as well. These could be viewed in various VR systems. However, it would absolutely not be recommended for a proper photogrammetric capture sequence.  It would most likely make your data worse.

 

We have some basic guidance for photogrammetric capture on our website here: http://culturalherit...ammetry/#how_to

 

We are working on a "Guide to Photogrammetric Image Capture" which will have a lot more detail, along with graphics and photos.  We expect to have it out before the end of the year.  it will be a free guide available under a Creative Commons license.

 

Carla

 

Thank you for the response Carla. I was not clear enough in my original post, I'm afraid. I will most certainly take a long series of photos around the objects (say 40-60 pictures from different angles). However, I was wondering if adding in so that each picture actually is stereoscopic, if there is any software that could take advantage of that (i.e. you punch in that there is a difference in viewpoint of x mm between it, and the software could use this as an additional level of accuracy enhancer). After posting, I found something called DI4D, that sounds kind of what I was thinking - though I suspect the price is more than a little prohibiting...and it is not clear to me whether you are always stuck to having only 2 cameras for each point in time (it talks about many frames, but I suspect this is for capturing a model that is animated, i.e. a person talking)



#4 GeorgeBevan

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Posted 29 September 2016 - 01:47 PM

The issue you're going to have with tools like the Kula is that the short stereo-base, similar to the distance between our eyes, is designed for stereo photography and video, not photogrammetry. Depth accuracy in photogrammetry is dependent on the ratio of the distance to the object and the distance between the cameras ("base"). The base is so short with the Kula that no additional accuracy would be gained, IMHO. You're right that there are a number of photogrammetry systems that do use stereo cameras, or even rigs with dozens of cameras, but this is primarily for instantaneous capture of moving subjects, like bodies and faces. 

 

I should say also that camera calibration with the types of split images produced by the Kula would be rather difficult.



#5 tosvus

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Posted 29 September 2016 - 05:24 PM

The issue you're going to have with tools like the Kula is that the short stereo-base, similar to the distance between our eyes, is designed for stereo photography and video, not photogrammetry. Depth accuracy in photogrammetry is dependent on the ratio of the distance to the object and the distance between the cameras ("base"). The base is so short with the Kula that no additional accuracy would be gained, IMHO. You're right that there are a number of photogrammetry systems that do use stereo cameras, or even rigs with dozens of cameras, but this is primarily for instantaneous capture of moving subjects, like bodies and faces. 

 

I should say also that camera calibration with the types of split images produced by the Kula would be rather difficult.

 

Thanks, that makes sense - I can see that would be issue!






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