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Shutter speed

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Offline jojo99

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Shutter speed
« on: 10 / June / 2008, 01:05:55 »
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I was experimenting with higher shutter speeds that CHDK enables this weekend.  It didn't work very well.  Seems the higher I bump the shutter speed, the darker the photo becomes (almost black in many cases).  I can bump the level a lot to see the actual photo image though.  I suspect that this effect is due to either the CCD or the lower quality lens on point and shoot cameras (can't get enough light in quick enough).  True? (btw: the lens was at F4 during these experiments.  I could go down to F2.8, which would let in some more light at the expense of depth of field).

Also, looking in the EXIF info for these higher shutter speed photo's, they all say 1/2004.12 in the shutter speed field.  Is CHDK able to communicate ITS shutter speed setting into the EXIF info?  If not, is there any way to tell what I had the CHDK shutter speed set to from the photo itself, or do I have to physically write this info down when shooting the photo?
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Offline dzsemx

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Re: Shutter speed
« Reply #1 on: 10 / June / 2008, 02:41:50 »
so...images becomes darker because you use higher shutter speed...(strange huh?)
have you ever tried Manual mode?
the exif info is made by camera firmware and the shutter speed is limited within 15- 1/2000(depends on camera) range by firmware
we override this
so the original firmware handles this situation by setting exif info to the nearest normal limits

btw feel free to modify sources for your own needs  :P:
https://tools.assembla.com/chdk/browser
« Last Edit: 10 / June / 2008, 02:48:17 by dzsemx »
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Offline jojo99

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Re: Shutter speed
« Reply #2 on: 10 / June / 2008, 04:08:30 »
Quote from: dzsemx on 10 / June / 2008, 02:41:50
so...images becomes darker because you use higher shutter speed...(strange huh?)
have you ever tried Manual mode?
What would you suggest I do in manual mode that would make a difference?

Quote from: dzsemx on 10 / June / 2008, 02:41:50
the exif info is made by camera firmware and the shutter speed is limited within 15- 1/2000(depends on camera) range by firmware
we override this
so the original firmware handles this situation by setting exif info to the nearest normal limits
So there is no way to find out the actual shutter speed used via CHDK from the photo only?

Quote from: dzsemx on 10 / June / 2008, 02:41:50
btw feel free to modify sources for your own needs  :P:
https://tools.assembla.com/chdk/browser
First I would have to learn to program :)
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Offline DataGhost

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Re: Shutter speed
« Reply #3 on: 10 / June / 2008, 04:55:20 »
Exiftool can read it from the Makernotes, it should be recorded in there. There is some tool around here (search) which copies the 'CHDK EXIF' into 'normal EXIF' using exiftool, so you don't have to worry about syntax. If you want to do it manually, you'll have to explicitly add -MakerNotes:ExposureTime -MakerNotes:FNumber -MakerNotes:ISO (or others) to the command line, you won't get them with -MakerNotes:All (in my experience).
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Offline fe50

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Re: Shutter speed
« Reply #4 on: 10 / June / 2008, 05:11:57 »
The "Auto CHDK to EXIF" utility (and the information for downloading) is in the wikia here. (ignore the raw/DNG things).

(from wikia: "...A small utility was created that allows you to process your JPG files to update appropriate EXIF fields with these non-standard CHDK override shutter-speed, aperture, and ISO values...."
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Offline jojo99

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Re: Shutter speed
« Reply #5 on: 10 / June / 2008, 06:01:31 »
OK, thanks for the EXIF pointer.  I will read up on this.

So back to the shutter speed issue.  Where would shutter speeds like 1/10000 be useful since it seems like my camera (at least) can't get enough light in for proper exposure?  It even has problems on a brightl sunny day at 1/2000 sec!  I was hoping to capture some tennis photo's of friends serving.  But given the light capture problem and the [overlooked] fact that the camera can only capture maybe 2 or 3 photos per second (if that), this doesn't look possible.

I think I need to look at real DLSR's.  Is there a CHDK for DSLR's (any brand)?  Is something like CHDK even needed with DSLR's?
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Offline fe50

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Re: Shutter speed
« Reply #6 on: 10 / June / 2008, 06:43:19 »
Quote
Where would shutter speeds like 1/10000 be useful since it seems like my camera (at least) can't get enough light in for proper exposure?

Look at the great pictures at Samples: High-Speed Shutter.. on the wikia and you'll see it  :)
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