SD1000/IXUS 70 ND Filter question/ allbest v 37. - AllBest's Builds - CHDK Forum
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SD1000/IXUS 70 ND Filter question/ allbest v 37.

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Offline icz

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SD1000/IXUS 70 ND Filter question/ allbest v 37.
« on: 27 / February / 2008, 23:42:12 »
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I'm using allbest latest v37 build.

I noticed that when switch nd filter to 'IN', the LCD screen looks darker, and shutter speed does not seem to change.
could there be a way to use larger apature when ND filter is 'IN',just like the Av mode?

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Offline pitquim

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Re: SD1000/IXUS 70 ND Filter question/ allbest v 37.
« Reply #1 on: 28 / February / 2008, 02:23:16 »
I'm not sure about this, but I believe that Ixus 70 doesn't have a real iris diafragm but only the ND filter: without filter f/2.8; with filter (like it was) f/8

if camera shows f/8, it's going to use the ND filter. You can avoid this with CHDK and use a higher shutter speed to compensate.
When camera shows f/2.8, you can force it to use the ND. As you said, screen go darker and camera won't cahnge the shutter speed. Do it yourself with Tv override.

When I had some spare time, I'll test these things.
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Offline icz

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Re: SD1000/IXUS 70 ND Filter question/ allbest v 37.
« Reply #2 on: 28 / February / 2008, 02:28:32 »
well, in that case, could the program 'auto' set a more reasonable shutter speed?
--Sounds like this is an enhancement request :)
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Offline ixus

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Re: SD1000/IXUS 70 ND Filter question/ allbest v 37.
« Reply #3 on: 28 / February / 2008, 11:01:55 »
The SD1000 has only 1 aperture, f/2.8.   f/8.0 is simulated by way of ND filter. This is the case in many low end cameras. If you point your camera from a dark scene to a light one, the click you hear is the ND filter kicking in.
See: IXUS800(SD700) inside the lens images. There is a ND filter!

If you set the ND filter in, and the cameras original firmware doesn't see the need for an ND filter, it will use shutter speeds as if there is no ND filter. The same thing happens when you set ISO settings manually in Allbest, you lose auto calculation of shutter speeds. I don't know if that is just the way CHDK/Allbest works or if its a bug. You need to triple (f/2.8->f/8.0=3 fstops, so multiply by 2^3=8) your shutter speed to compensate for ND filter.  So if your f/2.8 shutter speed is 0.5 seconds then your f/8.0 shutter speed would be 0.5*8=4 seconds. (I think, someone correct me if thats wrong)

And yes, there needs to be an AUTO setting in CHDK/Allbest for settings that you don't set manually.
« Last Edit: 28 / February / 2008, 11:10:31 by ixus »
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Offline pitquim

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Re: SD1000/IXUS 70 ND Filter question/ allbest v 37.
« Reply #4 on: 28 / February / 2008, 11:58:10 »
ixus: that's waht I described before... do you know if older Ixus-SD model works in the same way? I also own an Ixus55-SD450

thanks in advance
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Offline ixus

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Re: SD1000/IXUS 70 ND Filter question/ allbest v 37.
« Reply #5 on: 01 / March / 2008, 22:19:14 »
Who knows?
Take the camera from a dark scene to a light one and see if you hear the same clicking sound. I'm not exactly sure, but I don't think non-ND filter cameras with iris make the clicking sound. Maybe someone with an iris camera can tell us if it makes a clicking sound.
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Offline pitquim

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Re: SD1000/IXUS 70 ND Filter question/ allbest v 37.
« Reply #6 on: 02 / March / 2008, 02:55:28 »
I can hear exactly the same click :-)
thanks

...and I've made some test. Yes, the ND filter is in the Ixus55_SD450 too. And the CHDK's overrides work as expected
« Last Edit: 02 / March / 2008, 06:47:08 by pitquim »
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