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What camera to buy?

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Offline martos

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What camera to buy?
« on: 23 / December / 2010, 12:06:02 »
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Hi all,

This is my first time here do please excuse me if this one is not the right forum.

I am looking for some advice. I am working in several 3D computer vision projects for which it would be nice to have inexpensive and lightweight cameras enhanced using CHDK.

One of these project uses more than thirty A590 cameras, prepared for remote control and image download the 'hard' way.
Each camera has a few narrow wires installed, carefully soldered inside the body for external control of on/off button, shutter button, and mode selection switch (play/record). They also have external power and an USB cable to download images through PTP protocol.

The cameras are manually prepared with the same settings. A computer controlled sequencer turns the cameras on, sets 'record' mode, shoot each camera in sequence, sets 'play' mode, and images are downloaded via PTP.
Obviously I think this would be greatly improved using CHDK, but so far I am not sure if it is possible to switch modes remotely. Can someone give me some hint about how to do this using CHDK?
If not possible, do you know any other camera that can achieve that (switching between record and play mode remotely)

Thank you very much
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Offline reyalp

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Re: What camera to buy?
« Reply #1 on: 24 / December / 2010, 16:08:06 »
CHDKs experimental PTP interface is implemented on the a590 and some other cameras. This would allow you to change modes and shoot over PTP control.

You can check out the PTP interface thread for some information:
http://chdk.setepontos.com/index.php?topic=4338.0
and wiki page http://chdk.wikia.com/wiki/PTP_Extension

Note that this feature is experimental and still under development. You should *not* it expect it to work cleanly out of the box in every situation. I wouldn't suggest relying on it unless your fairly comfortable with hacking stuff (sounds like you are, based on your existing setup).

Some canon cameras can be controlled with canons SDK, but AFAIK none of the new low end cameras support this. See http://www.usa.canon.com/cusa/consumer/standard_display/sdk_homepage
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Offline martos

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Re: What camera to buy?
« Reply #2 on: 25 / December / 2010, 10:44:51 »
Thanks you for your reply.
I still need to find time to carefully read that threads and test CHDK's PTP support, but seems exactly what I was looking for.
 
Meanwhile I made some tests with the standard build. The latest one has a test script to change mode and it works!. Apparently I am able to shoot, switch mode via script, and then download using original camera PTP. It is nice to realize that it is possible to do this with this camera without wires.

Two smaller concerns arise however:

To switch back from play to record mode apparently I must unplug the USB cable. The camera gets stuck in PTP mode and I guess it would not react to a remote script or even to a timed script. Am I right? I wonder if this would be different using CHDK's PTP. It is no big problem anyway, since this can be hacked externally with a relay, but would be great if could be avoided. I will try.

The second problem is that the camera will not turn on when powered first time unless power button is pressed. I can disable power saving options and keep all cameras on all the time, but it is still a bit annoying to have to turn on so many cameras manually if power is lost, since some of them are not easily accessible. Unfortunately this will force me to keep at least a couple of the internal wires, which is disappointing...

Still, seems that CHDK it is going to help a lot.
Thank you.


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Offline reyalp

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Re: What camera to buy?
« Reply #3 on: 25 / December / 2010, 13:55:35 »
Quote from: martos on 25 / December / 2010, 10:44:51
To switch back from play to record mode apparently I must unplug the USB cable. The camera gets stuck in PTP mode and I guess it would not react to a remote script or even to a timed script. Am I right? I wonder if this would be different using CHDK's PTP. It is no big problem anyway, since this can be hacked externally with a relay, but would be great if could be avoided. I will try.
In the PTP builds, there is special code in some ports for switching play/rec while USB is connected. These currently use a special lua function switch_mode_usb to do this. I believe a590 is has this implemented.

Many older cameras (mostly vxworks ones) don't need special code, so you can use regular set_record. Many cameras do not have this feature implemented yet, so you'll want to check before you commit to buying a bunch of cameras.

Some people who wanted auto power-on have found the camera works if the power button is pressed all the time, so you can just make something to mechanically hold it down, and it will boot whenever power is applied. If this caused a problem on yours, you could probably mask the power switch in CHDK, as we do for the USB.
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