Tv bracketing starting point?

Psychokitty

121

Tv bracketing starting point?

« on: 11 / May / 2008, 07:58:33 »

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Hey folks,

I've searched the wiki and forum and Willy Lorenzo's recent PDF manual, to no avail. (-Just so you know...)

When I begin a shooting sequence using CHDK Tv bracketing in continuous mode, with the bracketing advance set to 1/3 Ev and "+", I would expect that I should be able to set the starting shutter speed somehow. Not having shutter priority on my camera, I'm not sure how to do this in CHDK.
The problem is that I wish to squeeze off a few quick shots but CHDK decides to start at a severely over-exposed speed like 1.6 seconds, for example. At 1/3 EV steps, I'm waiting several seconds to get the few shots in the exposure bracket I'm really interested in.
The start exposure is not always the same, but it's usually quite low.

-Is this aperture or ISO evaluation dependent?
I see no one else here complaining, so I'm certain I must be doing something wrong.

Thanks for your time.

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Jucifer

251
[A710IS]

Re: Tv bracketing starting point?

« Reply #1 on: 11 / May / 2008, 08:05:24 »

Try setting shutter speed override in extra photo operations.

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Psychokitty

121

Re: Tv bracketing starting point?

« Reply #2 on: 11 / May / 2008, 08:23:15 »

I set the override to 1/4 second, and the bracketing as explained above.
I made certain "Disable Overrides" was not checked.
It took the initial shot at 1/4 second, and then reverted to a 2.5 second exposure and went down from there.
(....also, shouldn't the bracketing for Tv be such that when it's set to "+" it climbs UP in exposure time? Just a little nit-picky thing.)

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Jucifer

251
[A710IS]

Re: Tv bracketing starting point?

« Reply #3 on: 11 / May / 2008, 11:44:32 »

Hm. Maybe some of the coders could help.

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fbonomi

469
A570IS SD1100/Ixus80

Re: Tv bracketing starting point?

« Reply #4 on: 12 / May / 2008, 05:41:42 »

Don't use override.

In my case (a570) it always starts from the current, standard settings of the camera,

So, you can set the camera in auto mode, and the first shot will be shot in auto mode, with default settings, with other shots being over (or under) exposed relative to the first one.

Alternatively, I go in manual mode, then manually set the desired Tv, then it brackets frm there.

Try disabling "Tv Bracketing in continuous mode" and just use the "plain" continuous mode. Do you get N identical exposures?

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Psychokitty

121

Re: Tv bracketing starting point?

« Reply #5 on: 12 / May / 2008, 07:56:30 »

I used "override" at Jucifer's suggestion. It makes no difference. The TX-1 doesn't have a manual Tv mode.

Quote

Do you get N identical exposures?

I don't understand... Are you asking if my Continuous mode is working correctly?
I do get the same speeds if I shoot something in continuous mode.

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Psychokitty

121

Re: Tv bracketing starting point?

« Reply #6 on: 12 / May / 2008, 08:06:21 »

I just tried setting Focus Lock on the camera, but that doesn't work either.
It still takes one shot at an appropriate speed, and then reverts to a slow shutter speed of 2.5 seconds, then decreases in speed in 1/3 Ev increments.
If I set the Ev to 2/3, the start speed is 2 seconds.
If I set the Ev to 1, the start speed is 1.6 seconds.
Ev = 1 1/3, starts at 1.3 seconds.
Etc...

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whoever

280
IXUS950

Re: Tv bracketing starting point?

« Reply #7 on: 13 / May / 2008, 03:07:36 »

Quote from: Psychokitty on 12 / May / 2008, 07:56:30

I used "override" at Jucifer's suggestion. It makes no difference. The TX-1 doesn't have a manual Tv mode.

That clarifies the things. The port to this cam was only recently made, it presented a lot of difficulties due to the hardware/software differences of TX-1 with respect to most other cams and due to the fact that none of the people that owned it were proficient in porting, and it is incomplete. Your observations, Kitty, suggest that the function in question just ain't working (yet?).

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Psychokitty

121

Re: Tv bracketing starting point?

« Reply #8 on: 13 / May / 2008, 06:30:10 »

Ahhh. I see...
Well, -How can I do my part to help?

...and I'm assuming this is a minor "calibration" type thing, correct? Or does this mean that when it says I'm shooting at 1/8000 sec, I'm really not?

« Last Edit: 13 / May / 2008, 06:33:11 by Psychokitty »

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whoever

280
IXUS950

Re: Tv bracketing starting point?

« Reply #9 on: 13 / May / 2008, 06:46:24 »

Quote from: Psychokitty on 13 / May / 2008, 06:30:10

Ahhh. I see...
Well, -How can I do my part to help?

If you're a programmer, then get the firmware disassembly, get CHDK sourses, and find how to make it work. If you are not a programmer, try to find one that has TX-1 and ask him/her. I believe that Microfunguy coordinated the porting effort, so maybe ask him first. I also heard that there's a TX-1 dedicated forum somewhere.

Quote

...and I'm assuming this is a minor "calibration" type thing, correct? Or does this mean that when it says I'm shooting at 1/8000 sec, I'm really not?

Not sure what you mean. What it says and what it does are different things, especially when the darn thing ain't working.

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