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av bracketing on Canon PowerShot SX210IS???

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av bracketing on Canon PowerShot SX210IS???
« on: 09 / June / 2013, 20:45:53 »
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Hi, I use CHDK with my old Canon PowerShot A720IS and use AV bracketing to do HDR shots.  It works beautifully.  All the shots of varying exposures that I can load into PhotoMatix. 

However, my brother gave me a newer Canon PoweShot SX210IS.  I put on the latest stable CHDK and set up the AV bracketing options the same way as on the A720IS (set the camera to AV mode, set continuous 5 shots with a 1 second initial delay, set 1/3 EV in the bracketing section under AV).  However, with the SX210IS, all the pictures come out with the same exposure!  I can't figure out what I'm doing differently on the SX210IS versus the A720IS (well, the SX210IS shows me more options than the A720IS but I'm not touching those settings).

Can anyone offer some advice?

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Offline reyalp

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Re: av bracketing on Canon PowerShot SX210IS???
« Reply #1 on: 09 / June / 2013, 21:08:31 »
What Canon shooting mode do you have it in? Is it the same one you used on the a720?

If the cameras chosen AV was at one of the limits, that could also cause bracketing to fail, though assuming you are using +/- mode, at least one shot should be different.

It's possible there's something broken in this port. It might be clearer to test whether Av overriding is working at all. I'd suggest something like:
Put the camera in P mode
Make sure canon auto-iso is off
Set a shutter speed override to something that will give you a recognizable image.
Set Av override to different values and compare the shots.

The overrides menu is described in http://chdk.wikia.com/wiki/CHDK_User_Manual#Extra_Photo_Operations
Don't forget what the H stands for.

Re: av bracketing on Canon PowerShot SX210IS???
« Reply #2 on: 09 / June / 2013, 21:08:54 »
Generally speaking,  I believe that most people use TV bracketing for HDR to get a bigger exposure range with the same focus and depth of field. And as most PowerShots do not have a variable aperture anyway that works out pretty well for them.

Having said that,  I tested the current CHDK release on my G10 - following the steps you outlined - and the Av varies shot to shot as expected.

Did you set your shooting up using [+/-] bracketing type?  If not,  you might have hit the limit of AV range for your camera (it does have a variable aperture but the ranges is very small - (f3.1 - f5.9 according to the literature - so you are not going to see a big exposure variation anyway).
Ported :   A1200    SD940   G10    Powershot N    G16

Re: av bracketing on Canon PowerShot SX210IS???
« Reply #3 on: 09 / June / 2013, 21:51:04 »
What Canon shooting mode do you have it in? Is it the same one you used on the a720?

If the cameras chosen AV was at one of the limits, that could also cause bracketing to fail, though assuming you are using +/- mode, at least one shot should be different.

It's possible there's something broken in this port. It might be clearer to test whether Av overriding is working at all. I'd suggest something like:
Put the camera in P mode
Make sure canon auto-iso is off
Set a shutter speed override to something that will give you a recognizable image.
Set Av override to different values and compare the shots.

The overrides menu is described in http://chdk.wikia.com/wiki/CHDK_User_Manual#Extra_Photo_Operations

Thank you for the response!  The camera is set to Av like the A720IS.  When you say +/- mode, do you mean bracketing type?  Yes, bracketing type is set to +/-.

None of the shots are different.  they all look the same (looking through the LCD screen on the camera).

I tried to follow your steps that you listed and went to the link that you listed but I got a little lost at the shuttle speed override step as I had never done that before.


Re: av bracketing on Canon PowerShot SX210IS???
« Reply #4 on: 09 / June / 2013, 21:54:15 »
Generally speaking,  I believe that most people use TV bracketing for HDR to get a bigger exposure range with the same focus and depth of field. And as most PowerShots do not have a variable aperture anyway that works out pretty well for them.

Having said that,  I tested the current CHDK release on my G10 - following the steps you outlined - and the Av varies shot to shot as expected.

Did you set your shooting up using [+/-] bracketing type?  If not,  you might have hit the limit of AV range for your camera (it does have a variable aperture but the ranges is very small - (f3.1 - f5.9 according to the literature - so you are not going to see a big exposure variation anyway).

Thank you for the response.  Very much appreciated as well.

Yes, +/- bracketing type is set in CHDK.  As far as I know, all the settings were set the same between the two cameras (in fact, I turned on the A720IS to check and mirrored the settings).

I can't imagine that the feature would work on the older A720IS and not on a newer SX210IS or that the A720IS would have better variable aperture.

I will try the Tv bracketing.  I had never done that before on the A720IS because I was very happy with the results of Av bracketing and remember that I got started with an article that said that Av bracketing would give better results.

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Offline reyalp

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Re: av bracketing on Canon PowerShot SX210IS???
« Reply #5 on: 09 / June / 2013, 23:24:12 »
Some cameras need an additional workaround for Av overrides to function correctly. I've attached a build with this enabled.

Regarding setting tv in my instructions,
set "shutterspeed enum type" to Ev Step
set "value factor" to 1
set override shutter speed to something reasonable, like what the camera shows if you half press in P mode without any overrides engaged.
Don't forget what the H stands for.

Re: av bracketing on Canon PowerShot SX210IS???
« Reply #6 on: 10 / June / 2013, 00:44:15 »
Some cameras need an additional workaround for Av overrides to function correctly. I've attached a build with this enabled.

Regarding setting tv in my instructions,
set "shutterspeed enum type" to Ev Step
set "value factor" to 1
set override shutter speed to something reasonable, like what the camera shows if you half press in P mode without any overrides engaged.

I tried the attached build that you provided and it worked!  Av bracketing worked with the steps that I was accustomed to!  You guys were extremely helpful.

Is this build the same as the stable build otherwise and i can just use this as my stable build?   :D

I will still experiment with Tv bracketing so thanks for that advice as well.
« Last Edit: 10 / June / 2013, 00:46:45 by dirtyvu »

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Offline reyalp

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Re: av bracketing on Canon PowerShot SX210IS???
« Reply #7 on: 10 / June / 2013, 01:04:52 »
Is this build the same as the stable build otherwise and i can just use this as my stable build?   :D
It should be pretty close, there might be some minor differences in compile time options. Anyway, I've checked the change in, so it should be in autobuild 2855 and later.

Thanks reporting this problem and testing.
Don't forget what the H stands for.


Re: av bracketing on Canon PowerShot SX210IS???
« Reply #8 on: 10 / June / 2013, 14:04:12 »
I will still experiment with Tv bracketing

You really should not use Av bracketing for HDR.
Apart from the problems waterwingz mentioned, your images will suffer a loss of sharpness as you stop down.

Tv bracketing is the  recommended  method.


 

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