ISO Bracketing on SD630 (firmware 1.00a) - AllBest's Builds - CHDK Forum

ISO Bracketing on SD630 (firmware 1.00a)

  • 6 Replies
  • 5151 Views
ISO Bracketing on SD630 (firmware 1.00a)
« on: 21 / November / 2008, 20:06:09 »
Advertisements
So I've read lots about how the built in bracketing works with Allthebest (and in general), but I can't quite get things working right on my SD630. I'd really like to have it take 3 pictures in "+/-" mode. I'd like them to be ISO bracketed (duh), something like 400/200/800 (that general idea). I'd like the flash to automatically fire if necessary on any given exposure, but I don't want to have to change anything per-exposure (hence the "auto" =] ).

I guess what I really need is someone to explain exactly what settings I need to configure to make this happen. Let's pretend I start with a bone-stock Allthebest config on SD630 (digi II platform, of course). I'm not sure if my dreams are reasonable with respect to getting the flash into auto mode, so even just getting the ISO part to work would be great.

I've tried things like setting the "ISO bracketing value" to, say, "4", and then "Value Factor" to about "100", but I'm getting unexpected behavior, for example the first two shots have differing ISOs, but the third is the same as the second. I've actually tried lots of permutations of the aforementioned values, everything from 1 to 10 on the former, and 1, 10, 100 on the second one.

Ideas anyone?

Here are a few useful pages I've found:
hdr images?
CHDK firmware usage/AllBest - CHDK Wiki
UBASIC/Scripts/CanonA640: ISO Bracketing - CHDK Wiki *
KAP Discussion Page - Easy bracketing with CHDK and any intervalometer script or shutter press


*I tried this and it doesn't work. It seems to be mostly a "macro" of simulated button commands, as opposed to manual configuration changes for camera settings. Since the buttons on the A640 are different from the SD630, it doesn't work.

Thanks!
Canon SD630

*

Offline fudgey

  • *****
  • 1705
  • a570is
Re: ISO Bracketing on SD630 (firmware 1.00a)
« Reply #1 on: 22 / November / 2008, 03:05:27 »
You need to write a script to do this, the internal override bracketing in continuous mode can't do it.

Continuous mode bracketing overrides the parameter (here ISO) right before each shoot in the burst. There are two problems with your approach that aren't compatible with this mechanism:

1) your camera doesn't even autoexposure again for each burst shot, only the first
2) even if it did that, the override is set by CHDK after AE, not before.

So, that bracketing will always give you a set of images with different brightnesses (unless you exceed camera limits and end up with images with effectively the same ISO).

Re: ISO Bracketing on SD630 (firmware 1.00a)
« Reply #2 on: 24 / November / 2008, 16:39:47 »
Thanks for the reply, but I'm actually a bit confused now... With regard to #1 - don't I want exactly that? I would like the camera to attempt to auto-expose for the first image only. For the second image it should go up by a certain ISO amount, then down for the third image.

Further confusion... Seems like I want "a set of images with different brightnesses", don't I? Isn't that sort of what bracketing is? (obviously bracketing is a complex and careful way to do that, but to the lay-person I would think, "images with different brightnesses" is a pretty good description of the effect bracketing has on a set of shots).
Canon SD630

*

Offline fudgey

  • *****
  • 1705
  • a570is
Re: ISO Bracketing on SD630 (firmware 1.00a)
« Reply #3 on: 24 / November / 2008, 17:45:22 »
Hm I guess I misunderstood you.

Never really tried ISO bracketing, my camera is no good at high ISO and it makes no sense for post processing to use it when I can do Tv bracketing which will generate frames that appear equally noisy. Furthermore, if ISO is set AUTO, the camera may choose an ISO that can't be increased or decreased (enough), causing bracketing to fail (unless you figure out how to use custom auto ISO, I guess). Tv can always be increased and decreased a lot from Canon's autoexposure range so bracketing will always succeed.


Re: ISO Bracketing on SD630 (firmware 1.00a)
« Reply #4 on: 25 / November / 2008, 15:35:46 »
I found UBASIC - CHDK Wiki and eventually PropertyCase - CHDK Wiki . I'll try to use those to write a script that is as generic as possible to do some nice bracketing and post back here when I've got it working.
Canon SD630

Re: ISO Bracketing on SD630 (firmware 1.00a)
« Reply #5 on: 21 / December / 2008, 17:01:39 »
How is the script coming? I have the same camera and looking to do hdr on it as well. I haven't coded in a while and things are looking cryptic.

Re: ISO Bracketing on SD630 (firmware 1.00a)
« Reply #6 on: 21 / December / 2008, 17:24:23 »
How is the script coming? I have the same camera and looking to do hdr on it as well. I haven't coded in a while and things are looking cryptic.
I haven't had a chance to work on it since I last posted, but I'm hoping I can spend some of my free time around these holidays to take a peek. From what I've seen it won't be too hard (famous last words)...
Canon SD630

 

Related Topics