Geotags, aerial synths, street synths… capturing events as they happen. If you can mark it on a map, then this is the place to talk about it.
Hi all, I'm seeking advice/ instruction on taking synths of tall structures. I've done this one that came out 97% synthy.
Hey there, Dwayne,
Sorry to be so long to reply.
I took a look at your synth and the four images that weren't connecting to the rest of the synth were images 1, 2, 142, and 143.
1 and 2 had matched each other but nothing else and 142 and 143 had matched each other but nothing else.
Just looking at it, I thought that since the monument was so small in those photos, that perhaps I would try an old trick from the Photosynth team ( https://getsatisfaction.com/livelabs/topics/don_t_crop_images#reply_585680 ) and make a copy of those photos and crop the copies to give Photosynth a little better look at the tower in those shots.
The idea is that the crop will match its parent image and if the crop connects to others in the synth, then the parents will connect to the rest of the synth via the crops.
I did a few experiments and it turns out that images 1 and 2 are able to be linked to the rest of the synth with crops that are just over a quarter of their parent images.
When I tried this on Images 142 and 143, the small crops usually synthed in to the rest of the photos, but since the size difference between the crops and the originals was greater than 2x the size ( See the bottom of Page 2 in the Photosynth Photography Guide http://photosynth.net/help.aspx#photosynthhelp ), the originals didn't link to the crops.
I tried again with the same small crops from Images 1 and 2, but changed to larger crops from Images 142 and 143 and found that this was the best for getting all the original photos into the synth with the fewest possible crops (one crop for each of the four straggler images).
Here's the final solution:
As far as general principles for shooting large structures, I can't offer too much beyond what is covered in the guide and video crash course ( http://bit.ly/howtosynth ).
If you've read my replies to others, you'll know that I've cherry picked orbits from both the Photosynth Photography Guide and the video as my favorite method of shooting parts of a scene.
What that would translate into for the monument is to circle the entire thing at a few different distances and then when I got close, then break the height of the tower up into three or four sections and then make sure that I had an orbit for each section if I wanted great resolution in the point cloud.
The other thing that occurs for me for tall outdoor objects is just that often your camera will be trying to expose for the sky, rather than the foreground. Photosynth needs a good exposure of the object you want a point cloud of and I'm guessing that's the tower, rather than the clouds.