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Max shutter time only 60 sec for A720

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Offline dvip

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Re: Max shutter time only 60 sec for A720
« Reply #10 on: 16 / December / 2012, 00:06:09 »
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>I decided to check the G1X (ported by philmoz). The exposure
>lasted the full 2 minutes. It works on the G1X (thanks philmoz!)

I hope it is working on the SX40HS and I can get 2 minutes or more.
I'm not sure if I can get 2 minutes on the A590IS either.


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Offline reyalp

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Re: Max shutter time only 60 sec for A720
« Reply #11 on: 16 / December / 2012, 00:06:47 »
Let me see if I understand this:

There is a limit of 64 seconds in the camera firmware.

You can get  64 seconds maximum with set_tv96_direct(-576)
Something like that, I'm not sure what the exact limit is.
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There is an extra long exposure patch in CHDK that removes the Canon 64 second firmware limitation by patching the machine code in the firmware that sets the limit.
It sets the override much later, in a different place.
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Activating extra long exposure depends on the patch being entered correctly, specifically for each camera and firmware version.
There's a large chunk of exp_drv_task that needs to be implemented.

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I checked my sx260 by setting long exposure over-ride to 2 minutes. I only got 64 seconds. I also get a maximum of 64 seconds with set_tv96_direct(...). But after reading this, I decided to check the G1X (ported by philmoz). The exposure lasted the full 2 minutes. It works on the G1X (thanks philmoz!)
So the patch doesn't seem to be installed correctly on the sx260. I'll check with nafraf to see if he can fix it.
The exp_drv_task is implemented on sx260, so it "should" work.

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I'm assuming that I can also set longer tv values on the G1X with set_tv96_direct(...) ?
Yes, any form of shutter override should work. Except setting propcases directly... edit: not correct, see following post.
« Last Edit: 16 / December / 2012, 17:25:45 by reyalp »
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Offline dvip

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Re: Max shutter time only 60 sec for A720
« Reply #12 on: 16 / December / 2012, 00:26:44 »
Using the A590IS got 2 minutes from chdk's menu [LongExp].

Re: Max shutter time only 60 sec for A720
« Reply #13 on: 16 / December / 2012, 02:04:27 »
>I decided to check the G1X (ported by philmoz). The exposure
>lasted the full 2 minutes. It works on the G1X (thanks philmoz!)

I hope it is working on the SX40HS and I can get 2 minutes or more.
I'm not sure if I can get 2 minutes on the A590IS either.

I have the SX40 as well as the A590.  On the A590, I have done 256 seconds.  I did a 512 seconds once but the battery was running out and in the end (camera did not shut down though) I just got a plain black image for that shot.  So I cannot say if the camera gave up because of the low power remaining, or if processing that much of an exposure was beyond it's capacity.



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Offline dvip

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Re: Max shutter time only 60 sec for A720
« Reply #14 on: 16 / December / 2012, 10:46:17 »
>I did a 512 seconds once but the battery was running out and in
>the end (camera did not shut down though) I just got a plain
>black image for that shot.

With the A590IS-101b, I got 2 minutes and a good image (JPG and DNG) from
chdk's menu [LongExp]. I have not tested the SX40SH-100i.


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Offline lapser

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Re: Max shutter time only 60 sec for A720
« Reply #15 on: 16 / December / 2012, 11:15:47 »
I'm assuming that I can also set longer tv values on the G1X with set_tv96_direct(...) ?
Yes, any form of shutter override should work. Except setting propcases directly...
Thanks for all the great info. You and the other chdk programmers have created an incredible piece of software.

I'm testing a new modification to set_tv96_direct(value) that uses the "SET_NOW" flag in half_shoot instead of "SET_LATER". It look like this sets propcases directly, and misses the long exposure override?

How about if you set a long exposure before pressing half_shoot, and then took a series of shots with shoot_full_only? Do you think it would hold the long exposure?

Why would I want to do that?

Shooting multiple long exposures with shoot_full_only minimizes the time between shots. If you also disabled dark frames, and maybe added a wide angle lens attachment, you'd have an optimum meteor catching technique.
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos

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Offline reyalp

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Re: Max shutter time only 60 sec for A720
« Reply #16 on: 16 / December / 2012, 17:25:08 »
I'm testing a new modification to set_tv96_direct(value) that uses the "SET_NOW" flag in half_shoot instead of "SET_LATER". It look like this sets propcases directly, and misses the long exposure override?
Apologies, I misremembered, so my answer wasn't correct. bad reyalp, ALWAY CHECK THE CODE! :-X

The "extra long exposure" override is done platform/generic/wrappers.c apex2us, which replaces the call to apex2us in the canon native firmwares exp_drv_task. It uses shooting_get_tv96 to get the value, which just reads the propcase, so setting the propcase directly should work, as long as it happens before that point is reached in exp_drv_task. When exactly that happens is not well specified, but it's probably after shoot_full starts.

edit: Note that this means if any canon firmware enforces the propcase value when it's set, this method will not work as is. I have a vague memory that something like this might have been encountered on some recent cameras?
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Why would I want to do that?

Shooting multiple long exposures with shoot_full_only minimizes the time between shots. If you also disabled dark frames, and maybe added a wide angle lens attachment, you'd have an optimum meteor catching technique.
The value of this seems dubious to me. If you are taking > 60 sec exposures, the effect of waiting 0.1 sec between exposures (without halfpress) or 0.5 sec (with half press) is not going to be very significant.
« Last Edit: 16 / December / 2012, 17:27:11 by reyalp »
Don't forget what the H stands for.

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Offline lapser

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Re: Max shutter time only 60 sec for A720
« Reply #17 on: 16 / December / 2012, 21:42:54 »
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Shooting multiple long exposures with shoot_full_only minimizes the time between shots. If you also disabled dark frames, and maybe added a wide angle lens attachment, you'd have an optimum meteor catching technique.
The value of this seems dubious to me. If you are taking > 60 sec exposures, the effect of waiting 0.1 sec between exposures (without halfpress) or 0.5 sec (with half press) is not going to be very significant.
True, but I'd hate to miss that big meteor that happened in that 0.4 seconds. I guess optimum is its own reward for me.

But there is a good reason to use continuous mode for long exposures, that I just discovered. When taking single shots, the display screen goes blank for the duration of the shot. But in continuous mode, holding the shutter down, the last picture is shown on the display for the duration of the next shot. You can actually see what your pictures look like. If you poll the set button during the shot, you can also toggle the back light off and on to save power.
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos


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Offline lapser

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Re: Max shutter time only 60 sec for A720
« Reply #18 on: 17 / December / 2012, 00:41:11 »
Nafraf sent me a patch for the long exposure bug on the sx260. It works great. Thanks Nafraf! I'm looking forward to seeing some really hot pixels.
EOS-M3_120f / SX50_100b / SX260_101a / G1X_100g / D20_100b
https://www.youtube.com/user/DrLapser/videos

 

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