Wednesday, May 27, 2009

Cannon EOS 450D/Rebel XSi woes.

Lately, I have been fussing with the camera, trying to control the shutter release mechanism remotely via my MacBook Pro. Ideally, it would have been nice to use a single library/front-end utility to control the shutter as well as download images from the camera. But I have run into some problems...

It seems that gphoto2 has problems taking control of the camera. I get the following error:

*** Error ***
An error occurred in the io-library ('Could not claim the USB device'): Could not claim interface 0 (m). Make sure no other program or kernel module (such as sdc2xx, stv680, spca50x) is using the device and you have read/write access to the device.

*** Error (-53: 'Could not claim the USB device') ***

Rather than spending my time troubleshooting this problem (gphoto2 support documentation for the mac is virtually non-existent), I brought up my Ubuntu virtual machine and installed the latest and greatest version (2.4.6) of libgphoto2/gphoto2 from the debian unstable repository. gphoto2 (2.4.5) under Ubuntu worked like a charm; I was able to grab a summary of the Camera status, and and configure it. Unfortunately, it seems that libgphoto2, does not support many of the remotely configurable features of this camera. The only parameters I was able to change were the focus lock and storage location of remotely captured images (device RAM/SD). These limitations, however, do not really affect me because all I really need to with the camera is remotely capture images and then grab them from the cam.

Also of note: Although the gphoto2 libraries for the 450D/Rebel XSi claim that you can remotely capture images to device RAM and SD, this functionality doesnt seem to actually work. The only way that I was able to capture images remotely was by using the --capture-image-and-download command line flag.

Because of the difficulty associated with getting gphoto2 up and running with this particular camera, accompanied by the fact that none of the camera options are configurable remotely by gphoto2, I am inclined to create a serial controller for the entire scanner setup. This serial controller would not only interface to the camera's 3/32" tether port, but would also provide an interface to the VXM stepper motor controller that would allow for the operation of the rig without an attached computer. Also, the controller would likely be able to do shutter control across the entire line of Canon SLR cameras.

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