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TV bracketing bug when using overrides

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Offline Atnas

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TV bracketing bug when using overrides
« on: 04 / October / 2009, 17:46:07 »
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When using TV overrides at the same time as TV bracketing, there is a bug.

If use CHDK overrides to set a 10 second shutter using EV step, TV bracketing uses the canon chosen shutter as seed for bracketing.
If I on the other hand set the 10 second shutter with factor instead of EV step, TV bracketing uses the CHDK overridden shutter speed as seed, as I would expect.

This sounds like a bug to me.
« Last Edit: 07 / October / 2009, 03:14:37 by Atnas »
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Offline reyalp

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Re: TV bracketing bug when using overrides
« Reply #1 on: 04 / October / 2009, 17:50:24 »
Which camera, what canon shooting modes ?
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Offline Atnas

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Re: TV bracketing bug when using overrides
« Reply #2 on: 04 / October / 2009, 17:54:54 »
SD1000 and A710
haven't thought about testing different shooting modes, did all my A710 tests in P and all my SD1000 tests in M
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Offline Atnas

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Re: TV bracketing bug when using overrides
« Reply #3 on: 04 / October / 2009, 18:12:16 »
More testing...

It is not mode dependent.

When using EV step it always uses a seed 5 stops below the correct seed. It is never related to the canon value, just always 5 stops below the actual seed.

Fx. if I set override of 1 second(with EV step), self timer with three shots, I get the exposures:
1"
1/15
1/60
« Last Edit: 04 / October / 2009, 18:16:01 by Atnas »
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Offline fe50

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Re: TV bracketing bug when using overrides
« Reply #4 on: 05 / October / 2009, 06:21:22 »
...solved for the A570 by fudgey here: http://chdk.kernreaktor.org/mantis/view.php?id=249
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Offline fudgey

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Re: TV bracketing bug when using overrides
« Reply #5 on: 06 / October / 2009, 15:12:21 »
Yes, a very similar bug was fixed for Tv bracketing since trunk 759 in May 2009, and universally affects all cameras (and a710 is very similar to a570).

That doesn't mean this isn't something new (I've probably never tested Tv override with anything but factor or Tv bracketing that would go anywhere near that slow), but logically the first question is....which CHDK version are you using?

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Offline Atnas

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Re: TV bracketing bug when using overrides
« Reply #6 on: 07 / October / 2009, 03:19:30 »
I am using latest autobuild of trunk, 813.

Problem summarized: When using shutterspeed override with EV step, and TV bracketing, the seed for bracketing is always 5 stops too low.

Not just affecting slow bracketing as I first thought
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Offline fudgey

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Re: TV bracketing bug when using overrides
« Reply #7 on: 07 / October / 2009, 13:39:20 »
Confirmed on my a570 too: Tv override combined with Tv bracketing only works properly if Tv override is set up using factor option, but not if it set up using the Ev step option.

By all likelihood the fault lies in the same place as before, i.e. platform/generic/shooting.c function shooting_tv_bracketing().


edit: I think adding extra long exposures to the enumerated list of Tv is what broke this (but the person who did that should not be blamed for it, he just ran into a trap :'(). If I'm not mistaken, this bug only exists on cameras that support extra long exposures (beyond 64 seconds). Anyway, I guess changing shooting.c line 1097 from
bracketing.tv96 = 32*(conf.tv_override_value-18);
to
bracketing.tv96 = 32*(conf.tv_override_value-tv_override_zero_shift);
will fix this.

I didn't test it yet.
« Last Edit: 07 / October / 2009, 14:06:19 by fudgey »
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Offline Atnas

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Re: TV bracketing bug when using overrides
« Reply #8 on: 07 / October / 2009, 14:18:34 »
Yes, that fixes the problem! :) Bracketing functioning as I'd expect it to. And I believe I even understand what was wrong :)
« Last Edit: 07 / October / 2009, 14:21:34 by Atnas »
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Offline Atnas

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Re: TV bracketing bug when using overrides
« Reply #9 on: 09 / October / 2009, 17:02:17 »
Shouldn't this be added to trunk somehow?

Not quite sure what to do, but attached a diff of it.
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