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USB remote: fast shooting

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Offline fabrizio.carraro

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USB remote: fast shooting
« on: 12 / August / 2015, 07:52:01 »
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Hi, I’m new on this forum, I hope this is the right place where to post a question. With my IXUS 230HS I need to shoot a long series of pictures. I don’t need refocusing so I use focus and exposure lock. The shoots have to be sync to an external trigger occurring about once a second. 
I’ve noticed that if I manually half press and then full press many times but without releasing the shoot button completely (so giving the sequence half - full - half -full etc) the camera can shoot a couple of frames/sec. If I release and full press every time the camera can only shoot a frame/sec. 
Now, using chdk:
Which is the right “switch type” and “control mode” to use in the “usb remote parameters” menu in order to simulate the half-full-half-full-half-full finger press? The pulse will be generated by a microcontroller. Can I just use the settings in the menu or should I use a script?
Thanks a lot
Fabrizio
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Offline waterwingz

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Re: USB remote: fast shooting
« Reply #1 on: 12 / August / 2015, 10:08:25 »
Quote from: fabrizio.carraro on 12 / August / 2015, 07:52:01
Can I just use the settings in the menu or should I use a script?
If you want to use the built-in settings then you probably need to try this : ]USB Remote : Burst Mode.

IIRC it might also be possible to do the equivalent of a held half press and then many full presses using the built-in CA-1 switch mode.

Be aware that getting shooting down to one frame per second or faster is difficult.  On some of the less expensive cameras its pertty much impossible.  So my suggestion would be that you use a  script.   You might  want to look at this wiki page KAP UAV Exposure Controller Script.  And there is a rather long ongoing thread about shooting at 1 fps rates sync'd to position over the ground by a flight controller starting approximately here : s110 shot interval under 1.5s
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline fabrizio.carraro

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Re: USB remote: fast shooting
« Reply #2 on: 12 / August / 2015, 12:15:11 »
Thank you waterwingz. Unfortunately I didn’t manage to simulate the manual half-full-half-full press. Burst mode sounds ok, but I don’t know how to put the camera in half press mode before using it. The CA-1 mode looked almost ok: after the first short pulse it beeps (without shooting) and on the second (long) one it shoots immediately without beeping. But at the next long pulse beeps again and then shoots. It looks like it needs the short pulse every time. It is useful in other applications because you can set focus and exposure in advance with the short pulse, then wait for the event you want to shoot. When the event arrives, send the long pulse and the shot is immediate. But it works only once. If the following pulse is long, it behaves like a normal shot (decide focus and exposure, then beeps and shot) which is too slow.
I’m really thinking something bad: avoiding using chdk and use a servo motor to mechanically push the button, calibrating it in a way it moves between half and full. Very bad, but in this way I can get 2 frames/sec!
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Offline waterwingz

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Re: USB remote: fast shooting
« Reply #3 on: 12 / August / 2015, 22:17:33 »
Quote from: fabrizio.carraro on 12 / August / 2015, 12:15:11
I’m really thinking something bad: avoiding using chdk and use a servo motor to mechanically push the button, calibrating it in a way it moves between half and full. Very bad, but in this way I can get 2 frames/sec!
If that works for you then you should consider it.  If it was me personally,  I'd use the kap_uav.lua script I linked above.  It gives you exposure control optimized for UAV operation,  startup and shutdown options,  logging of each shot, and the ability to shoot in continuous mode as fast as the camera can go.
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline fabrizio.carraro

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Re: USB remote: fast shooting
« Reply #4 on: 13 / August / 2015, 17:12:43 »
Ok waterwingz,
I'm new on scripts, this is the cause that made me decide to avoid them and look for another solution, but probably it is a good idea to spend some time and learn how to use them. Furthermore I imagine they will be the best way to set the presets I need about focus and exposure, avoiding to set them every time
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Offline waterwingz

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Re: USB remote: fast shooting
« Reply #5 on: 13 / August / 2015, 18:05:52 »
Like I said, take a look at the link I posted
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline fabrizio.carraro

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Re: USB remote: fast shooting
« Reply #6 on: 17 / August / 2015, 20:06:41 »
I learned a bit about scripts. They are really useful. Thanks waterwingz.
Anyway for some strange reason on my Ixus 230HS the fastest repetition rate is accomplished pressing half-full-half-full with a finger (or an actuator) without loading chdk. Maybe there are chdk extra functions still active that I'm not aware of, and they take some time to run. The fastest repetition rate with the following script is about 1,3 frames/sec. With the "finger" is about 0.5 seconds/frame. What can be the reason? Here is the script I use, triggered by a pulse on the usb:

press("shoot_half")
sleep(1000)
while 1 do  -- loop forever
   while get_usb_power(1) ~= 1 do   -- wait for usb pulse
      sleep(10) -- milliseconds
   end
   press("shoot_full_only")
   sleep(1) -- not necessary
   release("shoot_full_only")
end
release("shoot_half")
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Offline waterwingz

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Re: USB remote: fast shooting
« Reply #7 on: 17 / August / 2015, 20:29:16 »
Quote from: fabrizio.carraro on 17 / August / 2015, 20:06:41
What can be the reason?
The way that script is written, you don't check to see that the camera has actually finished the previous shot before trying to take the next one.

To see how this is supposed to be done, give this a try and see how fast it can shoot :  fastshot.lua
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Ported :   A1200    SD940   G10    Powershot N    G16
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