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Video exposure control, modified to work on Digic 4 camera's

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Offline srsa_4c

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Re: Video exposure control, modified to work on Digic 4 camera's
« Reply #20 on: 09 / April / 2013, 18:57:14 »
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Quote from: Davo on 09 / April / 2013, 10:30:35
I tried looking there for my A810 settings but no luck. Anyone know where I should be looking?
If your camera has the 1.00e firmware, see https://trac.assembla.com/chdk/browser/trunk/platform/a810/sub/100e/stubs_entry.S
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Offline Davo

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Re: Video exposure control, modified to work on Digic 4 camera's
« Reply #21 on: 10 / April / 2013, 04:35:36 »
Many thanks for that link - I can see where the 2 entries are.

I want to try locking the video parameters for astro work such as planetary animations and mosaics. If I try to record Jupiter, the auto exposure kicks in because of the dark night sky and Jupiter washes out. With lunar mosaics, I record a set of video tiles at high magnification to cover the whole surface. I then stack all the frames to give very sharp image tiles that I can merge just like a panorama. It is important that all tiles are recorded with the same exposure settings to give an accurate final image.
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Offline Davo

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Re: Video exposure control, modified to work on Digic 4 camera's
« Reply #22 on: 10 / April / 2013, 09:09:56 »
It works  :D

I had to load the German stable version just to try it out quickly but I can now adjust and lock shutter speed and ISO (or gain) for videos. I managed to record 2 sequences of 10s clips - first 65 clips and then 140 before it crashed. The crash cause was the same each time - I pointed it out the window at a very bright sky. Pointing it at a darker scene caused no problems.

I am now going to try to incorporate it into CHDKPTP for remote control astro work.

Thanks to the coders for this work.
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Offline Davo

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Re: Video exposure control, modified to work on Digic 4 camera's
« Reply #23 on: 11 / April / 2013, 07:54:16 »
My bad - I didn't need to load the German CHDK. I just needed to enable Lua native calls in the development version.

More experiments seem to indicate that the crash is caused at the start of a subsequent video clip if the exposure is much lighter or darker. Maybe I need to reset the parameters before each clip? I will give it a go.

Someone suggested that the Fast Ev switch does something similar and it does indeed seem to work. Does anyone know what this switch changes - shutter speed or gain or both?
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Offline Davo

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Re: Video exposure control, modified to work on Digic 4 camera's
« Reply #24 on: 13 / April / 2013, 09:40:44 »
A couple of other video hints that I found while experimenting.

You can use the Canon Live mode to alter brightness, saturation and color temperature which are then applied to the video record mode.

The Canon iFrame mode records 720p video where every frame is a key frame. (The normal 720p mode has a key frame every 12 frames or so which means that the camera estimates the intermediate or I-frames.) iFrame is great for astronomy because it means that every single frame is like a single snapshot. The downside is that iFrame videos have 50% bigger files.

I am hoping that iFrame with the CHDK video quality set at maximum will produce some superb results.
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Offline Microfunguy

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Re: Video exposure control, modified to work on Digic 4 camera's
« Reply #25 on: 13 / April / 2013, 10:38:23 »
Quote from: Davo on 13 / April / 2013, 09:40:44
iFrame is great for astronomy because it means that every single frame is like a single snapshot.

That is very interesting.

I have created stereo panoramas from the 640x480 MJPEG frames from an A620.
See the first panorama here http://www.stereomaker.net/panorama/panoramae.htm

The results have been better than trying to extract frames from so-called HD movies.
iFrames may be the answer for higher resolution panoramas.

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Offline bill.sikes.7

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Re: Video exposure control, modified to work on Digic 4 camera's
« Reply #26 on: 13 / April / 2013, 15:18:29 »
Beautiful work!  How large of a file is a full 360 degree pan?  Or, if it is a combination of files, what is the sum total of megabytes or gigabytes for one full cycle?  I'm sure they are not all the same size file(s) but what would be an average?  Just wondering what size card I would need to use to capture a panoramic view like this.
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Offline Davo

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Re: Video exposure control, modified to work on Digic 4 camera's
« Reply #27 on: 14 / April / 2013, 06:42:55 »
I would love to see details of how you produced that panorama. I have a motorised tripod head that might be perfect for it.

Update on increasing iFrame video quality - I can't. When I try to use the CHDK video quality option the video stutters and stops recording by itself. Also, there is a yellow exclamation box just to the left of the Canon time elapsed display. There is no mention of this in the manual. I guess iMatch is just on the limit of my camera/card (10speed) data transmit rate.
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Offline Microfunguy

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Re: Video exposure control, modified to work on Digic 4 camera's
« Reply #28 on: 14 / April / 2013, 08:28:42 »
Quote from: bill.sikes.7 on 13 / April / 2013, 15:18:29
How large of a file is a full 360 degree pan?

This is just a simple, old-fashioned 640x480 movie.
Don't know the size, not much, no big SD card needed.
The unusual thing is that this is a stereo panorama taken with a single camera.
The camera is rotated around a point that is behind it !
In effect, this creates a viewing circle of a certain diameter, for normal scenes that should be 65 to 75mm, the same as your eye-spacing.
For every narrow 'strip' in the scene, there will be two locations on the viewing circle from where it will be seen.
That means the strip is in stereo !
We extract lots of such strips and stitch into left and right panoramas which can be viewed in stereo, for example on a 3D TV.

I describe the procedure here http://stereo.jpn.org/eng/stphmkr/help/file_27.htm

The movie frames are extracted using VirtualDub.

In a moment of madness, in order to get an image height of 640, I mounted the camera vertically for the movie.

That will not work  .... of course   :)
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Offline danistuta

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Re: Video exposure control, modified to work on Digic 4 camera's
« Reply #29 on: 13 / May / 2013, 19:07:43 »
I've got sx240hs, is there a script to use for manual video settings? Let me know please. Thanks.
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