2.3 KiB
title, author, date, tags
| title | author | date | tags |
|---|---|---|---|
| Raspberry Pi pan-tilt mount for huge images, part 2 | Chris Hodapp | October 4, 2016 | photography, electronics, raspberrypi |
In my last post I introduced some of the project I've been working on. Those of you who thought a little further on this might have seen that I made an apparatus that captures a series of images from fairly precise positions, and then completely discards that position information, hands the images off to Hugin and PanoTools, and has them crunch numbers for awhile to derive the very same position information for each image.
That's a slight oversimplification - they also derive lens parameters, they derive other position parameters that I ignore, and the position information will deviate because:
- Stepper motors can stall, and these steppers may have some hysteresis in the gears.
- My pan and tilt axes aren't perfectly perpendicular.
- The camera might have a slight tilt or roll to it.
- The camera's entrance pupil may not lie exactly at the center of the two axes, which will cause rotations to also produce shifts in position that they must account for. (More on this will follow later. Those shifts in position can also cause parallaxing, which is much more annoying to account for. No, it's not the nodal point. No, it's not the principal point.)
That is, the position information we have is at best a guess; it's not sufficient on its own. However, these tools still do a big numerical optimization, and a starting position that is "close" can help them along, so we may as well use the information.
- We're using Panotools and our apparatus together; they can cross-check each other.
- Our position info also turns readily into a .pto file which Hugin can visualize.