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Time-Lapse movies with gphoto2

About

In this page I describe how to produce time-lapse movies using gphoto2. Everything started when a friend lent me his old Canon Powershot A40 digital camera. I then started experimenting with ghpoto2 to capture image and produce time-lapse movies of the clouds; there are plenty of such movies on YouTube, and I wanted to do my own.

Required software

This is the list of the required software:

Acquiring images with a digital photo camera

First, you need to acquire the snapshots somehow. gphoto2 can remotely control some digital cameras. The idea is to sit the camera on a tripod and let gphoto2 take pictures at regular intervals. gphoto2 allows the user to control different aspects of the camera (exposure time, aperture and so on). If you are using a Canon PowerShot A40, you must first put the camera in "Play" mode using the round selector on the back. Only in Play mode this camera can be remotely controlled.

Unfortunately, not all cameras can be remotely controlled. For those which can, it is possible to check which capabilities are supported using this command:

gphoto2 --list-config

The Canon PowerShot A40 display the following capabilities:

/main/camera/model
/main/camera/owner
/main/camera/capturesizeclass
/main/camera/iso
/main/camera/shutterspeed
/main/camera/zoom
/main/camera/aperture
/main/camera/resolution
/main/camera/focusmode
/main/camera/flashmode
/Main/camera/beep
/main/camera/datetime
/main/camera/setcameratime
/main/camera/firmwareversion
/main/camera/driver
/main/Driver/list_all_files

Unfortunately, it is not possible to remotely control all aspects of the A40; for example, shutterspeed and aperture can not be changed. This seems a limitation of the camera rather than gphoto2, as even the proprietary Canon Remote Capture application can not change these parameters. To change the value for a configuration parameter, you can use the following:

gphoto2 --set-config name=value ...

where name is the name of a parameter (e.g., /main/camera/flashmode) and value is one of the admissible values for it. You can figure out which are the admissible values by issuing this command:

gphoto2 --get-config name

If your camera supports remote capture, you should be able at least to do the following:

gphoto2 --capture-image-and-download --filename "%Y%m%d%H%M%S.jpg"

The --capture-image-and-download flag instructs gphoto2 to capture an image using the current camera settings and download it to the host PC. The --filename flag sets the filename for the image which will be saved on the local directory. In this case, each captured image will be named YYYYMMDDhhmmss.jpg, where YYYY is the year, MM is the month and so on. For example, 20080608080742.jpg is the name of the snapshot taken on june 8, 2008 at 08:07:42AM. Using this naming scheme has the advantage that the lexicographic order of the file names is the same as the chronological order in which the images were taken. This will help mencoder to assemble the images in the right order.

Capturing with the Canon Powershot A40

This is the list of values which are currently accepted by some of the configuration variables for the Canon PowerShot A40. Note that your camera might have different names for the configuration variables, and these might take different values.

/main/camera/iso

Choice: 0 ISO 100
Choice: 1 ISO 125
Choice: 2 ISO 160
Choice: 3 ISO 200
Choice: 4 ISO 250
Choice: 5 ISO 320
Choice: 6 ISO 400
Choice: 7 ISO 500
Choice: 8 ISO 640
Choice: 9 ISO 800
Choice: 10 ISO 1000
Choice: 11 ISO 1250
Choice: 12 ISO 1600
Choice: 13 ISO 3200
Choice: 14 Unknown


/main/camera/zoom

Choice: 0 No zoom
Choice: 1 1
Choice: 2 2
Choice: 3 3
Choice: 4 4
Choice: 5 5
Choice: 6 6
Choice: 7 7
Choice: 8 8
Choice: 9 Zoom 9 (max)
Choice: 10 Unknown


/main/camera/resolution

Choice: 0 RAW
Choice: 1 Small Normal JPEG
Choice: 2 Small Fine JPEG
Choice: 3 Medium Normal JPEG
Choice: 4 Medium Fine JPEG
Choice: 5 Large Normal JPEG
Choice: 6 Large Fine JPEG
Choice: 7 RAW + Small Normal JPEG
Choice: 8 RAW + Small Fine JPEG
Choice: 9 RAW + Medium Normal JPEG
Choice: 10 RAW + Medium Fine JPEG
Choice: 11 RAW + Large Normal JPEG
Choice: 12 RAW + Large Fine JPEG


/main/camera/focusmode

Choice: 0 Auto focus: one-shot
Choice: 1 Auto focus: AI servo
Choice: 2 Auto focus: AI focus
Choice: 3 Manual focus


/main/camera/flashmode

Choice: 0 Flash off
Choice: 1 Flash on
Choice: 2 Flash auto
Choice: 3 Flash red eye removal
Choice: 4 Flash on (assist light fires)


/Main/camera/beep

Choice: 0 Beep off
Choice: 1 Beep on

The specific capture command which I used with the Canon A40 was the following:

gphoto2 --set-config beep=0 --set-config flashmode=0 --set-config resolution=3 -I 20 -F 3150 --capture-image-and-download --filename "%Y%m%d%H%M%S.jpg"

the meaning of each parameter being:

--set-config beep=0
Disable the beep which is normally emitted by the camera when it focuses the image
--set-config flashmode=0
Disable the flash
--set-config resolution=3
Acquire the image at medium resolution (1024×768)
-I 20
Use a 20 seconds interval between two snapshots
-F 3150
Capture 3150 snapshots

In general, to get a smooth video you should use a small value of the -I parameter. For my A40 it was not reasonable to set an interval less than 10 seconds, as taking the picture and downloading it to the host took around 6 seconds.

This is a sample picture taken on 2008-06-08 at 09:59:22

Snapshot taken on 2008-06-08

Labeling the images

Sometimes it is useful to overlay the timestamp to each frame, so that the movie will contain a visual indication of the capture times. Labeling images is quite easy to do using just ImageMagick and a little bash scripting. Create a script named label_image.sh with the following content:

#!/bin/sh if [ ! -f $1 ]; then echo "$1 not found" exit -1 fi text=`identify -format "%[EXIF:DateTime]" $1` width=`identify -format %w $1` convert $1 -gravity southeast -pointsize 40 \ -stroke black -strokewidth 4 -annotate 0 "${text}" \ -stroke white -strokewidth 1 -fill white -annotate 0 "${text}" \ "caption_$1"

Invoking label_image.sh 20080608095922.jpg will create a new image caption_20080608095922.jpg with the timestamp on the lower right corner, like this:

Snapshot taken on 2008-06-08, with the timestamp on the lower right corner

Making the movie

Now that you have a directory full of pictures, it is possible to make a movie from them using MEncoder. The command I used is the following:

mencoder "mf://*.jpg" -mf fps=12:type=jpg -ovc lavc -lavcopts vcodec=mpeg4:mbd=2:trell:vbitrate=7000 -vf scale=640:480 -oac copy -o movie.avi

This produces an mpeg4 stream inside an AVI container. The output framerate is 12fps, and each image is rescaled at 640×480 resolution before encoding. This command will produce a high-quality, LARGE file. Just to give you an idea, encoding 3150 frames will produce a movie of 192289210 bytes (see later).

To produce a FLV movie you can use the following command

ffmpeg -i movie.avi -s qvga movie.flv

This produces a lower quality movie at qvga resolution (320x240), but with a significant reduction in file size (movie.flv takes only 6618134 bytes). You can view the resulting movie using a FLV-capable movie player, such as MPlayer or VLC. It is also possible to embed the .flv movie in a web page using Flowplayer, an open-source Flash movie player. You can see the result here:

The video quality can be improved by using a higher bitrate; this can be done with the -b brate flag of FFmpeg, where brate is the bitrate in bits/second (default is 200kb/s).

The following table summarizes the space requirements of different movie formats at different bitrates.

Movie size comparison
Encoding File size (bytes) Quality
Raw images: 3150 medium quality JPEGs, 1024×768 each 363355038 Original
mencoder "mf://*.jpg" -mf fps=12:type=jpg -ovc lavc -lavcopts vcodec=mpeg4:mbd=2:trell:vbitrate=7000 -vf scale=640:480 -oac copy -o movie.avi 192289210 Excellent
ffmpeg -i movie.avi -s qvga movie.flv (default bitrate 200kb/s) 6618134 Good (small picture)
ffmpeg -i movie.avi -s qvga -b 150000 movie.flv 5036483 Fair
ffmpeg -i movie.avi -s qvga -b 100000 movie.flv 3494717 Poor

Using a webcam to capture snapshots

Sadly, my friend's trusty A40 broke down (more details below), so I tried to experiment using a webcam to capture snapshots. A webcam has a much more simple electronics than a digital photo camera, and has no moving parts. For this reason, it represents a good candidate for taking plenty of pictures reliably. Moreover, with a webcam you are able to achieve a higher capture rate.

Unfortunately, it turns out that cheap webcams often provide poor image quality. One of the webcams I tested (a Creative Live! Cam Optia) is useless for taking outdoor pictures, as it produces overexposed images. Probably the webcam sensor is somewhat optimized for low light conditions, as in fact it produces good images with very dim light.

At the time I wrote this page, I tested the following webcams:

I used fswebcam to acquire a snapshot every 10 seconds.

The Logitech Quickcam Pro 9000 is the best one in term of image quality, and in my opinion it is strongly recommended for taking outdoor pictures. Moreover, Logitech is actively supporting open source development on their cameras. Unfortunately it appears that newer QuickCam Pro 9000 models are affected by a firmware problem which might make them unstable under Linux.

The Creative Live! Cam Optia produces severely overexposed outdoor images, but nevertheless works fine in dim light conditions. I do not recommend it for outdoor use. The old Trust webcam has overexposure problems as well, but the images are not as overexposed as the ones produced by the Optia. Unfortunately, the image quality of the pictures taken by the SpaceCam 300 is very bad: images are blurred regardless how you adjust the focus ring.

The following two pictures were taken with a Panasonic Lumix FZ7 digital photo camera (left) and with the Creative Live! Cam Optia (right). As you can see, the picture taken with the Creative Live! Cam lacks any detail in the bright areas.

Panasonic Lumix FZ7

Outdoor snapshot taken with a Panasonic Lumix FZ7 digital photo camera

Creative Live! Cam Optia

Outdoor snapshot taken with the Creative Live! Cam Optia

The following two pictures were taken with the Logitech Quickcam Pro 9000 (left) and Creative Live! Cam Optia (right). Both snapshots were taken exactly at the same time.

Logitech Quickcam Pro 9000

Outdoor snapshot taken with the Logitech Quickcam Pro 9000

Creative Live! Cam Optia

Outdoor snapshot taken with the Creative Live! Cam Optia

As can be seen, there are no visible features in the image taken with the Creative Live! Cam Optia webcam. Also, note that the image is somehow yellowish (the yellow tint can be improved by playing with the gamma correction control of the camera). Also, there are problems setting the exposure manually on the Live! Cam Optia; manual exposure works fine under Windows, but also with minimum exposure values the image is overexposed anyway, exactly as the snapshots above.

Later, I bought a Logitech Quickcam E3500, which is a cheap UVC-compliant camera which produces reasonable images at 640×480 resolution. More information are available on a separate page.

Reliability Considerations

After some thousands pictures taken as described above resulted in TWO broken cameras, a few considerations are in order. Apparently, (cheap) digital photo cameras are not built to sustain heavy usage such as taking picture continuously. My PowerShot A40 broke first, resulting in "washed out" images. Then I got a PowerShot A80, which worked fine for a while until it broke down as well. The A80 started producing very dark (almost black) images, with occasional violet stripes and other artifacts. I suspect that it got affected by the issue described in this Canon advisory (see also a longer explanation). Unfortunately, the Canon repair center I contacted did not recognize the issue and was not willing to repair the camera for free, so I have thrown the camera away.

If should be observed that I may have been unluky: I know of a PowerShot A70 which is happily taking pictures every 5 minutes since many years without any issue, so YMMV. As far as I'm concerned, I'm going to experiment a bit more with cheap UVC-compatible webcams, as they don't have moving parts, the USB communication with the host PC is more reliable, and recent models have a sufficient image quality.

Resources

  • fswebcam is a very nice program to capture snapshots from a USB camera.
  • Canon SDK Documentation page. Contains a comprehensive list of remote capture capabilities of many Canon digital cameras; note that the page refers to Canon official SDK only, so cameras listed there are not necessarily supported by gphoto2. Nevertheless, if a camera is reported not to support remote control with the Canon SDK, it won't be supported by gphoto2 as well.
This page was last updated on January 11 2017 informativa sulla privacy