S110 AE-lock for still images - General Discussion and Assistance - CHDK Forum
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S110 AE-lock for still images

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Offline mr.burns

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S110 AE-lock for still images
« on: 23 / April / 2015, 02:59:33 »
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Hi,

the Canon Powershot S110 has a built-in function for AE-lock.
If the shutter is half pressed and the 'Up' key is pressed then the AE is locked. But this is not very comfortable.
Is there any command in CHDK which locks the AE as well?

What I want to have is AE-lock by pressing just one button.
Can I use CHDK and make e.g. the 'function' button working like AE-lock button?

Thanks...
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Offline msl

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Re: S110 AE-lock for still images
« Reply #1 on: 23 / April / 2015, 07:16:33 »
You need the half pressed shutter for the results of Tv & Av. After that you can lock AE.

The best way is a script with press/release ("shoot_half") and set_aelock() .

msl
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Offline mr.burns

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Re: S110 AE-lock for still images
« Reply #2 on: 23 / April / 2015, 11:22:58 »
Hi thanks msl,

can I do it in CHDK using C language as well?

Is it a precondition that I have to half press first? This would mean the focus is locked as well?
With digital DSLR (like e.g. Nikon D5500, Lumix GH3)  I can set AE lock without half pressing the shutter.
With those cameras I can pan the cam and aim at an object and press the AE-lock button, AE is locked now.
Now I can pan back and focus a different object, half press to focus and full press to take a picture.
This I want to copy for my S110. So focus is on a different object than AE lock.

Here is what I want/need for my S110 in steps:

1. Pan the cam to object A, press 'function' (or other) button --> AE gets locked
2. Pan the camera back, aim a different object B, half press the shutter to focus object B
3. Full press to take a picture of object B
4. AE lock should be unlocked now

I want to develop this using CHDK an C language, can it be done?
« Last Edit: 23 / April / 2015, 11:26:43 by mr.burns »
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Offline waterwingz

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Re: S110 AE-lock for still images
« Reply #3 on: 23 / April / 2015, 12:20:22 »
Quote from: mr.burns on 23 / April / 2015, 11:22:58
can I do it in CHDK using C language as well?
Yes.  If you want to build and maintain your own custom version.

Edit : if you wanted this to become a permanent part of CHDK, the "normal" process to add a feature is to :
  • start a forum thread to discuss the proposed feature
  • make a case for why the feature could not just be done with a script
  • propose how the new feature would be implemented
  • discuss any limitations about implementing the feature on all cameras or indicate an appropriate build option
  • write code to implement the feature, test,  and then post a patch file in your forum thread
  • seek feedback on the implementation
  • recode, rework, and provide updates until a consensus is reached
  • post the final patch file here : http://chdk.setepontos.com/index.php?topic=650.0
  • profit !

Quote
Is it a precondition that I have to half press first?
Half press just tells the camera to focus and set the exposure. You can probably find the underlying routines for both and do them separately but it will take some work.

Quote
This would mean the focus is locked as well?
That depends on how you implement it.  You can do the half-press, read the exposure, release the half press and then use the measured exposure values at the next shot.  That will allow a refocus.
« Last Edit: 23 / April / 2015, 12:49:56 by waterwingz »
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Offline mr.burns

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Re: S110 AE-lock for still images
« Reply #4 on: 24 / April / 2015, 02:45:19 »
Hi,

thanks msl and waterwingz that gives me a good starting point.
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