Video exposure control, modified to work on Digic 4 camera's

Stimpy

Video exposure control, modified to work on Digic 4 camera's

« on: 12 / February / 2011, 19:57:59 »

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The Following script requires that you find your camera's specific "ExpCtrlTool_StopContiAE" and ExpCtrlTool_StartContiAE" memory locations.

My IXUS 100IS settings were obtained here,
http://my-trac.assembla.com/chdkde/browser/trunk/platform/ixus100_sd780/sub/100c/stubs_entry_2.S?rev=455

They happen to be
NHSTUB(ExpCtrlTool_StopContiAE, 0xFF830084) //"StopContiAE"
NHSTUB(ExpCtrlTool_StartContiAE, 0xFF82FF40) //"StartContiAE"

Note, unless you're using an IXUS 100, they WILL be different.
Find you settings and substitue in the script below

-- go to manual exposure mode

I changed the script to have the "SET" button initiate and stop movie recording from within the script.
A big thanks to fudgey who created the initial script and all others who have helped along the way!

I'm sure this script can be culled back to the bare essentials, please offer suggestions.

Videxp.lua (8.4 kB - downloaded 385 times.)

« Last Edit: 07 / March / 2011, 06:58:33 by Stimpy »

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reyalp

13230

Re: Video exposure control, modified to work on Digic 4 camera's

« Reply #1 on: 12 / February / 2011, 20:54:17 »

Not really sure this belongs in "completed and working", it should be regarded as highly experimental.

It also requires a CHDK build with http://chdk.wikia.com/wiki/Lua/Lua_Reference/Native_Function_Calls

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Don't forget what the H stands for.

Stimpy

Re: Video exposure control, modified to work on Digic 4 camera's

« Reply #2 on: 14 / February / 2011, 07:33:50 »

Yes, perhaps this would've been better posted in the LUA section, due to the custom CHDK build requirements.

I've been testing this script thoroughly over the past few days, it does seem to be very reliable on an IXUS 100is. I lock the exposure as a first step before running the script, I've never had auto-exposure kick in yet using this method.
Having zero gain does seem to help the h.264 compression, as it's not trying to compress all that noise.

I'd be interested to know which other camera's this script works on? (particularly the S95 and G12 cams).
To the Devs, what's the likelihood this could be "hard-coded" into the CHDK main menu??? (once enough people have successfully test on their various camera's).

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emutier

Re: Video exposure control, modified to work on Digic 4 camera's

« Reply #3 on: 14 / March / 2011, 16:34:08 »

so... I have a S95, an I'm very interested, but I do NOT know, how to get this to work. What do I have to change in the script? thx

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matth

Re: Video exposure control, modified to work on Digic 4 camera's

« Reply #4 on: 12 / May / 2011, 20:07:08 »

Hi @emutier,

You'd need to change the memory addresses in the manualexp and autoexp functions.

If you have either the 100e or 100h firmware on your S95, you should change the manualexp and autoexp functions to the following (I'm using the Videxp.lua script from the first post as the starting point):

"
function manualexp()
ret=call_func_ptr(0xFF8474E4,0,0)
end
function autoexp()
ret=call_func_ptr(0xFF84734C,0,0)
end
"

And you'd need a build of CHDK with native function calls (see reyalp's post above).

I haven't tested this myself yet (don't have a working build environment to do a build with native function calls). It'd be great to hear if it works for you, and which firmware you're using.

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matth

Re: Video exposure control, modified to work on Digic 4 camera's

« Reply #5 on: 12 / May / 2011, 20:23:47 »

For those using this script, it's worth avoiding the case where the exposure time is greater than the interval between video frames. E.g. for a frame rate of 24fps, best not to try a shutter speed of 1/15sec.

Apart from the fact that it wouldn't make sense to use such settings, I have a hunch that it can contribute to crashes, based on some results in the original thread for this script, e.g. an attempt to set a 1/4sec shutter speed [1].

[1] http://chdk.setepontos.com/index.php?topic=5295.msg54071#msg54071

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emutier

Re: Video exposure control, modified to work on Digic 4 camera's

« Reply #6 on: 13 / May / 2011, 18:04:17 »

Quote from: matth on 12 / May / 2011, 20:07:08

I haven't tested this myself yet (don't have a working build environment to do a build with native function calls). It'd be great to hear if it works for you, and which firmware you're using.

thx, neither have I... maybe I will check how to do that stuff the next days

1/15 at 1/24 movie... nice idea ;-)
but 1/48 (= cinema) would be niiiiiice!!!

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curttard

Re: Video exposure control, modified to work on Digic 4 camera's

« Reply #7 on: 23 / August / 2011, 18:44:51 »

I'm attempting to try this out on an S95 using the script and script alteration posted here. It just tells me my firmware doesn't support native calls, despite the fact that I checked that option in CHDK-Shell when compiling. I also modified the buildconf.inc manually to un-comment out that line and then compiled, but I still get the error.

Also, assuming I ever get it to work, how would I go about setting a specific shutter speed? Like the poster above, my goal is 1/48 for a more film-like look.

« Last Edit: 23 / August / 2011, 18:50:45 by curttard »

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curttard

Re: Video exposure control, modified to work on Digic 4 camera's

« Reply #8 on: 24 / August / 2011, 11:16:26 »

Got it working. I will figure out what numbers = what shutters speeds, apertures, and ISOs and post them here if anyone is interested.

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peekay1977

Re: Video exposure control, modified to work on Digic 4 camera's

« Reply #9 on: 29 / September / 2011, 05:39:40 »

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