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Custom AutoISO

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Offline mkmenuts

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  • SD700 (1.01b)
Custom AutoISO
« on: 24 / January / 2008, 15:01:29 »
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Is it possible to add this to CHDK:

Custom Auto ISO (selectable maximum ISO, minimum shutter speed)?

I tried it with a script but it was very cumbersome. This would allow choosing the max ISO you feel is useful (considering noise and print size, for example).

I believe this is available on SD870, and might prove useful on other cams.

mkmenuts

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Offline mkmenuts

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  • SD700 (1.01b)
Re: Custom AutoISO
« Reply #1 on: 31 / January / 2008, 07:55:16 »
I'd like to post some more info to get comments (I'm implementing it myself, as there was no real excitement...).

This is, BTW, an improvement on a very useful feature available in DSLR Nikons and SD870.

Custom AutoISO feature:
This will allow the camera to choose the right ISO automatically from user-defined range (for example: expand the SD700 AutoISO from 80-200 to 50-400).
The camera will try to maintain lowest ISO as long as shutter speed is no-slower than user defined.
AutoISO will kick-in whenever ISO HI is chosen, to allow quick override by user to any ISO including the "old" Auto ISO. If you want the "old" ISO HI, just disable AutoISO in the CHDK menu.

Example: Camera set ISO 100 at 1/8s. AutoISO configured to ISO50-400 at 1/15s:
AutoISO will shift to ISO200 to maintain 1/15s shutter speed.
This feature should be available in all modes except for S(hutter priority) and M(anual).

The feature is enabled in menu, where the user enter ISO range and minimal shutter.

Support different min shutter values depending on IS mode and focal length:

   1. The Auto ISO minimum shutter speed to include user adjustable aperture multiplier and include

      The min_shutter value would be calculated from user=1/aperture/X
      X is user settable as 0.5 or 1.5 or 2 (I guess 0.5-4 range in 0.5 increments)
   
   2. IS (image stabilizer) factor which changes the min_shutter. Example:
      min_shutter = 1/30s, IS factor = 4 (default=1, 1-4 range in 0.5 increments)
      turning IS on will change min_shutter to 1/8 (1/30*4)

Do you prefer to go by focal length (35mm equivalent?) instead of aperture? Other comments?

mkmenuts

Re: Custom AutoISO
« Reply #2 on: 31 / January / 2008, 16:49:58 »
Hi mkmenuts,

worked out very well.

AutoISO will kick-in whenever ISO HI is chosen...

Ingenious!

Do you prefer to go by focal length (35mm equivalent?) instead of aperture?

The average IXUS/SD user would probably prefer zoom point or focal length, since there is no aperture drive.

Why not using the already present menu entry 'OSD/Misc/Zoom value: X, FL, EFL' a second time to let the user choose it's preference ?



Please upload any IXUS800/SD700 preliminary build when available.

nirschi

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Offline mkmenuts

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  • SD700 (1.01b)
Re: Custom AutoISO
« Reply #3 on: 05 / February / 2008, 08:16:58 »
I put the feature here: http://chdk.wikia.com/wiki/SD700_CHDK_Porting

EDIT: Beware. alpha software! My camera hangs occasionally.

Please put comments in this thread.

mkmenuts
« Last Edit: 05 / February / 2008, 13:48:17 by mkmenuts »


Re: Custom AutoISO
« Reply #4 on: 06 / February / 2008, 05:25:18 »
Hi mkmenuts,
it will be very useful functionality!!!  :o
I have a SD700 fw 1.00b camera, for which CHDK port already exists, too. Using SVN client I've just checked out current CHDK release (svn checkout https:// tools.assembla.com/svn/chdk/trunk) but there is no Custom AutoISO option. I think, it is due to your release is not at stable stage yet and what I am downloading is some last stable release.
Please, tell me, what I should enter as a SVN parameters to get your "Custom Auto ISO (alpha) release" (branch)?
I'd like to compile it for my 1.00b firmware version and test it.
Thanks in advance!

Re: Custom AutoISO
« Reply #5 on: 06 / February / 2008, 09:41:15 »

Hi mkmenuts,

had the camera with me one evening and yet missed the easy access to "old" ISO HI badly (for social snaps without flash).
A slight change and it would be perfect:

Let AutoISO kick-in whenever 'ISO AUTO' or  'ISO HI'  is choosen and allow 'Max ISO AUTO' and 'Max ISO HI' set independendly in the config menu (default 400 vs. 800). That's all!

And User Factor (1/FL/factor) is not really intuitive.

Cheers nirschi

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Offline mkmenuts

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  • SD700 (1.01b)
Re: Custom AutoISO
« Reply #6 on: 09 / February / 2008, 07:57:47 »
Quote
had the camera with me one evening and yet missed the easy access to "old" ISO HI badly (for social snaps without flash).
A slight change and it would be perfect:

Let AutoISO kick-in whenever 'ISO AUTO' or  'ISO HI'  is choosen and allow 'Max ISO AUTO' and 'Max ISO HI' set independendly in the config menu (default 400 vs. 800). That's all!

Good suggestion, will do it soon. Glad to hear this is working for you in general.

Quote
And User Factor (1/FL/factor) is not really intuitive.

Actually, the user mode has a different goal. Here's the logic behind it:

1. If you choose a specific speed, then you are referring to subject type (e.g Kids 1/60, Sports 1/250)
2. If you Choose User mode, then you're shooting still-life (e.g. Landscapes) and want to get sharp photos at minimal shutter speed & ISO, regardless of focal point (the bigger the focal point, the faster the shutter speed needed). This assumes you are shooting handheld with or w/o IS. If you use a tripod, it has not meaning

I hope that clears it up, people need to make sure to switch to a specific ISO (e.g. 80) when putting the camera on a tripod, and disabe IS.

An idea I had was to automatically turn off IS whenever specific ISO is chosen (and custom AutoISO in On, of course), what do you think?

mkmentus

Re: Custom AutoISO
« Reply #7 on: 09 / February / 2008, 12:15:40 »
Quote
I hope that clears it up, people need to make sure to switch to a specific ISO (e.g. 80) when putting the camera on a tripod, and disabe IS. An idea I had was to automatically turn off IS whenever specific ISO is chosen (and custom AutoISO in On, of course), what do you think?

I understand. But I never studied negative side effects of IS using the camera on tripod.
Are there any? ???



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Offline mkmenuts

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  • SD700 (1.01b)
Re: Custom AutoISO
« Reply #8 on: 09 / February / 2008, 13:27:18 »
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I never studied negative side effects of IS using the camera on tripod.
Are there any?

On some cameras, the IS detects the tripod and shuts-off. From my SD700 tests, it is better to manually turn off IS for long (over 1 second) exposures.

mkmenuts

Re: Custom AutoISO
« Reply #9 on: 09 / February / 2008, 14:14:20 »
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« Last Edit: 22 / April / 2008, 11:23:11 by Barney Fife »
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