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Custom Auto ISO not consistent on Elph 110HS

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Offline PhiPi

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Custom Auto ISO not consistent on Elph 110HS
« on: 09 / June / 2015, 19:17:17 »
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I'm using a USB-triggered uBASIC program to take underwater photos from a floating ROV. A fast shutter is essential to eliminate motion blur. So I've enabled Auto ISO in the function settings and the following for CHDK's Custom Auto ISO:

Enable [•]
Min Shutter [1/250]
...
Min ISO [50]
Max ISO Auto [3200]
Fallback Min Shutter [1/125]
Fallback Max ISO [3200]
OverExp Comp [Off]
...

In some of the photos, the Min Shutter is honored; in others, not. For example, in one photo the shutter speed was 1/40, and the ISO 100. There was significant motion blur.

This is CHDK 1.3.0, rev 4019, FW ver. 101a.

Any ideas what's going on?

Thanks,
-Phil
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Offline waterwingz

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Re: Custom Auto ISO not consistent on Elph 110HS
« Reply #1 on: 09 / June / 2015, 19:24:57 »
Do you have the camera in P mode rather than Auto ?  See page 78 here : ELPH110 IXUS125 User Guide

I'm also not sure how well the CHDK Auto ISO function will work with a uBASIC script. There is another scripting option you could try with full autoISO / fastest shutter speeds capability and USB remote support : KAP UAV Exposure Control Script - disable the CHDK autoISO "feature" if you use this.
« Last Edit: 09 / June / 2015, 19:27:53 by waterwingz »
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline srsa_4c

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Re: Custom Auto ISO not consistent on Elph 110HS
« Reply #2 on: 09 / June / 2015, 19:30:09 »
Servo AF (and perhaps a few other features) can also have a bad influence on CHDK overrides.
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Offline PhiPi

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Re: Custom Auto ISO not consistent on Elph 110HS
« Reply #3 on: 09 / June / 2015, 19:40:44 »
I'm using P mode. Should I be using Auto instead? Also, I do have Servo AF enabled. Perhaps I should disable it.

-Phil
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Offline waterwingz

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Re: Custom Auto ISO not consistent on Elph 110HS
« Reply #4 on: 09 / June / 2015, 21:02:15 »
Quote from: PhiPi on 09 / June / 2015, 19:40:44
I'm using P mode. Should I be using Auto instead? Also, I do have Servo AF enabled. Perhaps I should disable it.
Stick with P mode. 

I wrote up some suggested Canon setting for one of my script.  But they probably apply to most scripts.   

The list is here : Camera Setup

Having said that,  the CHDK code for "Custom Auto ISO" is somewhat ... ummm .. interesting.  Not sure it would get added to the build today but it has been there for a while.  YMMV.

Edit :  Can you post your uBASIC script?  From the sounds of your application, you may not even need a script at all. But I'd like to see what you are doing.  For example. if you try to shoot too quickly you may "overrun" the custom Auto ISO function.
« Last Edit: 09 / June / 2015, 21:06:24 by waterwingz »
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline PhiPi

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Re: Custom Auto ISO not consistent on Elph 110HS
« Reply #5 on: 09 / June / 2015, 22:25:32 »
Here's my script:

@title ASV Cam
set_console_layout 0 0 20 6
sleep 1000
set_zoom_speed 25
set_zoom 15
sleep 1000
do
  do
    sleep 50
    a = get_usb_power(0)
  until a > 0
  if (a < 20) then shoot
  if (a > 50) then shut_down
until 0


In the external program that triggers the USB V+ pin, I'm allowing about four seconds between exposures. I hope that's enough.

BTW, I have noticed that when using the half press technique, if you wait too long before doing a full press, the camera takes over the exposure settings, regardless of what your programmed preferences are.

Thanks,
-Phil
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Offline waterwingz

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Re: Custom Auto ISO not consistent on Elph 110HS
« Reply #6 on: 09 / June / 2015, 23:02:50 »
Quote from: PhiPi on 09 / June / 2015, 22:25:32
Here's my script:
Thanks for posting that.  It looks okay.  Incidentally,  set_zoom_speed is reported to only work on a few cameras but using it probably does not hurt anything.

Quote
In the external program that triggers the USB V+ pin, I'm allowing about four seconds between exposures. I hope that's enough.
That should be fine.

Quote
BTW, I have noticed that when using the half press technique, if you wait too long before doing a full press, the camera takes over the exposure settings, regardless of what your programmed preferences are.
I'm not sure but that could be an effect of using continuous autofocus or tracking autofocus?
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline PhiPi

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Re: Custom Auto ISO not consistent on Elph 110HS
« Reply #7 on: 09 / June / 2015, 23:09:59 »
Quote
Incidentally,  set_zoom_speed is reported to only work on a few cameras but using it probably does not hurt anything.
My experience has been that it you don't do a set_zoom_speed first, set_zoom doesn't do anything.

Anyway, is my only recourse now to try it without ServoAF, or are there still other things to look for?

Thanks,
-Phil
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Offline waterwingz

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Re: Custom Auto ISO not consistent on Elph 110HS
« Reply #8 on: 09 / June / 2015, 23:30:29 »
Quote from: PhiPi on 09 / June / 2015, 23:09:59
Quote
Incidentally,  set_zoom_speed is reported to only work on a few cameras but using it probably does not hurt anything.
My experience has been that it you don't do a set_zoom_speed first, set_zoom doesn't do anything.
Strange.  I have written a few script that many people use that use set_zoom without a set_zoom_speed.  And tested them myself on six different camera models.

Quote
Anyway, is my only recourse now to try it without ServoAF, or are there still other things to look for?
That's all I have for you.   Someone else might have additional thoughts.

Still, there is the link I posted to a script that handles the auto ISO functionality in the script as well as remote shooting.  After more than 3000 downloads,  I'm pretty sure it works correctly.
« Last Edit: 09 / June / 2015, 23:37:18 by waterwingz »
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline PhiPi

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Re: Custom Auto ISO not consistent on Elph 110HS
« Reply #9 on: 10 / June / 2015, 00:13:34 »
Thanks for the help! I've changed my settings to correspond to your recommendations and will try that first. Failing that, it looks like what you've done in your auto ISO script will be have to be the next step.

-Phil
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