---
title: "Pi pan-tilt for huge images, part 1: introduction"
author: Chris Hodapp
date: September 23, 2016
tags: photography, electronics, raspberrypi
---

Earlier this year I was turning around ideas in my head - perhaps
inspired by Dr. Essa's excellent class,
[CS6475: Computational Photography][cs6475] - about the possibility of
making an inexpensive, relatively turn-key rig for creating very
high-detail photographs, ideally in HDR, and taking advantage of
algorithms, automation, and redundancy to work with cheap optics and
cheap sensors.  What I had in mind had a pretty commonly-seen starting
point for making panoramas - something like a telephoto lens mounted
on a pan-tilt gimbal, and software behind it responsible for shooting
the right pattern of photographs, handling correct exposures,
capturing all the data, and stitching it.

My aim wasn't so much to produce panoramas as it was to produce very
high-detail images, of which panoramas are one type.  I'd like it to
be possible for narrow angles of view too.

Most of my thoughts landed at the same inevitable view that this would
require lots of custom hardware and electronics, and perhaps from
there still may need a mobile app to handle all of the heavy
computations.

Interestingly, this whole time I had several Raspberry Pis, an
[ArduCam][] board, work history that familiarized me with some of the
cheaper M12 & CS mount lenses of the telephoto variety, and access to
a [hackerspace][hive13] with laser cutters and CNCs.  Eventually, I
realized the rather obvious idea that the Pi and ArduCam would
probably do exactly what I needed.

A few other designs (like [this][makezine] and [this][scraptopower])
offered some inspiration, and after iterating on a design a few times
I eventually had something mostly out of laser-cut plywood, hardware
store parts, and [cheap steppers][steppers]. It looks something like
this, mounted on a small tripod:

[![](../images/2016-09-25-pi-pan-tilt-1/IMG_20160912_144539.jpg){width=100%}](../images/2016-09-25-pi-pan-tilt-1/IMG_20160912_144539.jpg)

I am able to move the steppers thanks to [Matt's code][raspi-spy] and
capture images with [raspistill][].  The arrangement here provides two
axes, pitch and yaw (or, pan and tilt).  I put together some code to
move the steppers in a 2D grid pattern of a certain size and number of
points.  (Side note: raspistill can
[capture 10-bit raw Bayer data][forum-raw-images] with the `--raw`
option, which is very nice.  I'm not doing this yet, however.)

Here's a video of it moving in such a pattern (to speed things along,
image capture was replaced by a 1/2 second delay at each point):

<iframe width="560" height="315"
src="https://www.youtube.com/embed/jO3SBandiUs" frameborder="0"
allowfullscreen></iframe>

It's still rather rough to use, but it worked well enough that I
picked up a [25mm M12 lens][25mm-lens] - still an angle of view of
about 10 degrees on this sensor - and set it up in the park for a test
run:

[![My shot's not slanted, the ground is](../images/2016-09-25-pi-pan-tilt-1/IMG_20160918_160857.jpg){width=100%}](../images/2016-09-25-pi-pan-tilt-1/IMG_20160918_160857.jpg)

(*Later note*: I didn't actually use the 25mm lens on that shot.  I
used a 4mm (or something) lens that looks pretty much the same, and
didn't realize it until later.  It's a wonder that Hugin was able to
stitch the shots at all.)

The laptop is mainly there so that I can SSH into the Pi to control
things and to use [RPi-Cam-Web-Interface][] to focus the lens.  The
red cord is just Cat 6 connecting their NICs together; the Pi is
running off of battery here.  If I had a wireless adapter on hand (or
just a Raspberry Pi 3) I could probably have just set up a WiFi
hotspot from the Pi and done all this from a phone.

I collected 40 or 50 images as the stepper moved through the grid.
While I fixed the exposure and ISO values with raspistill, I didn't
attempt any bracketing for HDR, and I left whitebalance at whatever
the camera module felt like doing, which almost certainly varied from
picture to picture.  Automatic whitebalance won't matter when I start
using the raw Bayer data, but for the first attempt at stitching, I
used only the JPEGs which already had whitebalance applied.

I stitched everything in Hugin on my desktop PC.  I would like to
eventually make stitching possible just on the Raspberry Pi, which
isn't *that* farfetched considering that I stitched my first panoramas
on a box that wasn't much more powerful than a Pi.  I also had to get
rid of some of the images because for whatever reason Hugin's
optimization was failing when they were present.  However, being able
to look at Hugin's computed pitch, yaw, and roll values and see
everything lining up nicely with the motion of the steppers is a good
sign.

The first results look decent, but fuzzy, as $10 optics are prone to
produce:

[![](http://i.imgur.com/zwIJpFn.jpg){width=100%}](http://i.imgur.com/zwIJpFn.jpg)

Follow along to [part 2](./2016-10-04-pi-pan-tilt-2.html).

[cs6475]: https://www.omscs.gatech.edu/cs-6475-computational-photography
[ArduCam]: http://www.arducam.com/camera-modules/raspberrypi-camera/
[hive13]: http://hive13.org/
[makezine]: http://makezine.com/projects/high-resolution-panorama-photography-rig/
[scraptopower]: http://www.scraptopower.co.uk/Raspberry-Pi/raspberry-pi-diy-pan-tilt-plans
[steppers]: https://www.amazon.com/Elegoo-28BYJ-48-ULN2003-Stepper-Arduino/dp/B01CP18J4A
[raspi-spy]: http://www.raspberrypi-spy.co.uk/2012/07/stepper-motor-control-in-python/
[forum-raw-images]: https://www.raspberrypi.org/forums/viewtopic.php?p=357138
[raspistill]: https://www.raspberrypi.org/documentation/raspbian/applications/camera.md
[RPi-Cam-Web-Interface]: http://elinux.org/RPi-Cam-Web-Interface
[25mm-lens]: https://www.amazon.com/gp/product/B00N3ZPTE6
[Hugin]: http://wiki.panotools.org/Hugin
