Arm lengths for very wide angle cave-floor pictures?

[sea_ledford]

Tilting out with shorter arms should work as well. I still suggest as wide as possible on the arms though. My understanding of the photogrammetry 3d modeling software is that it is fairly forgiving of camera setups, you will just have to take more images. I assume you know about the GUE photogrammetry facebook group? I just joined a week or so ago looking for info myself.

Are you trying to get full 3D maps of cave interiors? That would be awesome. I'm trying to do the opposite and get 3D maps of offshore oil platforms.

-Chris

 

[Aotus]

yeah, I know about the group. I started using photogrammetry in caves a few years ago, but nothing serious until a year ago in the Dominican Republic. Still, then was only a proof of concept mission. This summer I will be collecting data for my research, and the easiest way to go would be to use the equipment I used in the DR last year, but that equipment is unavailable, and I am now building a dedicated rig for the work. My biggest concern is that I haven't worked with strobes before, but took the risk of a new approach because for they give me more light for my limited budget, and I am only taking stills. I'm super nervous about getting it right with the new equipment however, and I don't have time to go dive a cave somewhere before my trip to practice. So, my house in the dark, and a neighbor's pool will be my only practice arena.

A vendor just recommended I go with the 8" arms (so, two 8" arms on each side) because longer than that gets very cumbersome with the small camera. I'm still torn. I was going to pull the trigger on 12" but now 8 or 12...

 

[sea_ledford]

Two 8" on each side will work. With the knuckles, that will give you a 10" spread on each side. I guess it depends how big the cave is though. I've only taken my rig into a cave a couple times, and that was in Phantom Springs which is just a big tube for the most part, so it wasn't nearly as cumbersome as I was expecting. Being able to fold it up into a fairly compact package to transport though tight spots made me more comfortable with the idea. I was more worried about scratching the dome.

 

[Aotus]

the caves are pretty spacious. there are some restrictions, but my belly and tanks are a lot bigger than my camera rig.

 

[Aotus]

UPDATE: I ordered a pair of 8" arms. I'll post a pic when i have it all set up. thanks for the comments and suggestions.