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"Automatic" exposure override possible?

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"Automatic" exposure override possible?
« on: 23 / September / 2008, 21:50:01 »
I have the S3 and SX100, and unfortunately Canon decided to cripple these cameras by implementing a maximum exposure time of 1 second when on automatic settings. The result is that time lapses go black once it gets dark even though the metering is still accurate and could be used to set the correct exposure. See here:

CHDK is capable of both accessing the metering values and overriding the exposure parameters. In principle this allows for an "extended automatic mode" where correct exposure parameters are calculated (or fetched from a table, whichever works) based on the metering value and then used instead of Canon's crippled exposure parameters. This would allow these cameras to do smooth day/night transitions which is a bit of a "holy grail" for time lapse shooters (because DSLRs give flicker; compacts go black).

I read in the CHDK manual about overriding settings, but I am not sure I understand quite how it works. I tried playing with it on my S3, but I could only manage to override the shutter speed with one specific value; not one that changes based on the metering. Is CHDK capable of doing this? If so, can someone guide me a little? If not, is it something that could be implemented and should be put on the wish list?

On a side note, can anybody confirm whether the main CCDs are used for metering on these cameras? Many DSLR users think that metering on DSLRs must be better, but DSLRs have to use secondary sensors which may just be good enough for metering, but still not as sensitive as the main CCD in a compact (note how the DSLR in the test video above only does 1/8 ev exposure steps while the S3 does 1/32 ev steps).
SX100, S3


Offline Hacki

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Re: "Automatic" exposure override possible?
« Reply #1 on: 23 / September / 2008, 21:56:37 »
Hm.. there's a script around, which does exactly what you want, i blieve.

Maybe this: Night-time time-lapse

If not, just search for 'night time lapse'

Re: "Automatic" exposure override possible?
« Reply #2 on: 24 / September / 2008, 07:00:25 »
All I can say is: Thanks a lot. You people are my heros. :-)
SX100, S3


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