Re: [Elphel-Eyesis] Panoramas From the Backpack
- --- In PanoToolsNG@yahoogroups.com, "Uri" <uri@...> wrote:
> What I saw was not too impressive; lack of focus, poor stitching, uneven horizon, huge nadir hole, all for over $24,000! or did I miss something?"
Update (by Andrey)
There is a nice discussion of these panoramas on a PanoToolsNG forum:
"That's of course just my snobbish sight on it because I can't see a reason why one would want to take the pain to carry such a thing just to bring horrible pictures from beautiful places to the rest of the world."
What I saw was not too impressive; lack of focus, poor stitching, uneven horizon, huge nadir hole, all for over $24,000! or did I miss something?
Well, these panoramas are not perfect, of course. But I got an impression that it is an apples-to-oranges comparison (you may find more an apples-to-apples one in our previous blog post). The panoramas we tried here were made with a rig designed to be mounted on a car roof, the backpack version was a quick test (we actually planned this trip to try camera on ATV, but we had to change our plans for the reasons out of our control), so nothing was done to make a camera vertical that would need either angled mount of the optical head or (as a quick fix) a counter-balance attached to the camera (something like a carrot on an stick extending in front of an operator). That tilt caused the black nadir hole being asymmetrical, you may want to look at our project under development Eyesis-4pi it is designed to have the same resolution in the zenith and a zero nadir void but there still will be some vehicle or person visible, unless the camera will be in a free fall (i.e. in space) as we were already suggested :-) .
The camera we used simultaneously acquires all 9 images in a way that there are no voids even when the camera is moving fast, so we acquired thousands of panoramas during each of the trips, the acquisition rate was set to about 2 frames per second. Yes, you definitely can make artistic panoramas using a single inexpensive camera using adapter that keeps the entrance pupil of the lens in the same point, but that would not work for the fast moving camera so our only tool to keep the parallax low was to design the camera to have components as close as possible but the parallax would never be zero
Poor focus? Well, this may be true for the very close objects, the camera is designed for the relatively high distance to the objects. The focus is fixed, of course, and the lenses are rather high power to avoid motion blur when the camera is moving at highway speed. So with f=4.5mm and F=2.0 the near limit of the DoF is approximately 6 meters, in our experiments we had much closer shots too. The lenses are also limiting the resolution (especially near the edges of the images), and we went a long way to improve the quality by postprocessing. You may analyze the raw/processed images pairs used in one of these panoramas by our image comparison tool (works in FF better than in Chrome).
Currently this postprocessing only corrects aberrations (not the distortions), so the panoramas are stitched manually. We never invested much time into perfecting the panorama stitching, because we have to do it automatically in the end, and we plan to make a camera to be a measurement tool, able to precisely locate the position of each pixel. The software (it is all under GNU GPLv3) can currently measure the position of the calibration pattern (same one as we use for aberrations correction) is already capable of detecting the pattern nodes locations to the +/-0.05 pixels precision, but the overall pixel mapping processing is not finished yet. We'll describe this calibration procedure more on our blog when finished.
Levelling the panoramas yes, it is lousy too. We already have built the hardware for the IMU (inertial measurement unit)integration, that allows logging the high resolution sensor data (we use ADIS-16375) at the full senor rate (300Hz), we also made the hardware for 5Hz (or higher) GPS integration, including the precise timing pulses. Unfortunately, I was not able to finish the FPGA code for the data logger during that our trip, so the panoramas lack that important data and we'll have to try again when ready (it will have odometer/pedometer input also).
We are a Free Software/Open Hardware company, and while we can not give away our cameras (and yes, they are much more expensive than a simple panoramic adapter you can use to make brilliant panoramas), our software is all under GNU GPLv3 license, we "release early" (all the software we use internally is maintained at Sourceforge), our camera documentation is also available under Free license. And we are inviting other developers, who have ideas and experience in the panoramic imaging to join this project.
Andrey via tom