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Daytime long exposure - problems with over exposure - IXUS 70 (SD1000)

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Offline Bellsy1000

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Daytime long exposure - problems with over exposure - IXUS 70 (SD1000)
« on: 12 / August / 2008, 03:15:29 »
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Offline fbonomi

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Re: Daytime long exposure - problems with over exposure - IXUS 70 (SD1000)
« Reply #1 on: 12 / August / 2008, 03:27:58 »
My camera does not have an ND-filter, but as far as I know the bult-in ND has a limited range, and is used just to bring exposure within a "reasonable" range (i.e. a range useful to the standard usage a user would do of a point-and-shoot camera).

A 5 seconds daytime exposure is not within a "reasonable"  range, so in a certain way you are trying to do too much for your particular camera?

A partial workaround could be to have multiple exposures and then to average them out. If you take 40 shots of a waterfall and then you average them out you will have an effect that is similar to a long exposure.

Similar, but not identical, though.... It should b ok for a waterfall, but surely not fo a long exposure of people moving: in this case you won't have a single, motion blurred image of a person, but rather several still images of faded-away persons, like some ghosts.

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Offline frank

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Re: Daytime long exposure - problems with over exposure - IXUS 70 (SD1000)
« Reply #2 on: 12 / August / 2008, 05:32:39 »
Maybe you just put a black paper with a small whole in front of the lens?
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Offline fbonomi

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Re: Daytime long exposure - problems with over exposure - IXUS 70 (SD1000)
« Reply #3 on: 12 / August / 2008, 06:27:07 »
mhh.  interesting.. that would give you an extreme depth of field :-)
but maybe interferences would disturb the image
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Offline Hacki

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Re: Daytime long exposure - problems with over exposure - IXUS 70 (SD1000)
« Reply #4 on: 12 / August / 2008, 07:52:39 »
Quote from: fbonomi on 12 / August / 2008, 06:27:07
mhh.  interesting.. that would give you an extreme depth of field :-)

Unfortunately not. It would give you a black image with a white spot in the middle. To simulate a pinhole camera, you either have to build one which can be attached to the lens, so you can photograph the image projected to a 'canvas', or you'd have to remove the lens assembly entirely.

To topic: I can confirm that its not possible to take a 5" exposure in daylight. Even with aperture override set to f/16 (which my camera can actually do, i think) its overexposued. Although, its possible to take 5" exposures in dimmed areas. Inside rooms, in a forest, and so on. Although, if its really that important to you - you could try to get your hands on a ND filter made for SLR's, and hold it in front of your lens.

regards,
hacki
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Offline fudgey

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Re: Daytime long exposure - problems with over exposure - IXUS 70 (SD1000)
« Reply #5 on: 12 / August / 2008, 08:34:15 »
Also zoom in fully to get rid of some light (and on cameras with aperture, I believe you need to do that to achieve the F/16 override for real).
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Offline LjL

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Re: Daytime long exposure - problems with over exposure - IXUS 70 (SD1000)
« Reply #6 on: 12 / August / 2008, 10:06:08 »
I wonder if it might be possible to perform a CCD readout while keeping the shutter open for further light gathering (not unlike what the camera does when taking movies)... that way it would be possible to take seamless long exposures without the CCD clipping, by averaging multiple readouts in real-time (although, of course, you'd have the disadvantages of an "electronic shutter").
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Offline RaduP

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Re: Daytime long exposure - problems with over exposure - IXUS 70 (SD1000)
« Reply #7 on: 12 / August / 2008, 11:37:16 »
Do you really need 5 seconds for waterfalls? I just took some waterfall picturees a week ago, and it seems that even 1/20" shows nice, smooth water.
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Offline Bellsy1000

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Re: Daytime long exposure - problems with over exposure - IXUS 70 (SD1000)
« Reply #8 on: 13 / August / 2008, 02:52:44 »
Thank you for your help everyone. 

I realise that I am probably asking too much from my "point and shoot", but I've been inspired to try and do as much as i can with it since being introduced to CHDK a couple of months ago.  It seems that I'm just not satisfied with not being able to do something now :) - if that makes sense.

I've found improved results by zooming all the way in, cutting out a lot of light - thanks Fudgey.

I'm also toying with the idea of buying a Cokin ND Filter that can be attached to point and shoot digital cameras, but that might be a project for another day.

Cheers and thanks everyone.

A big thankyou to everyone who has contributed to CHDK and made it what it is.  I have virtually no understanding of the programming and behind the scenes work that has gone on, but it has breathed new life into my canon and it is (as we all know) an amazing program.

Cheers
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