Continuous shooting repeat bracketing

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    Continuous shooting repeat bracketing
    « on: 07 / July / 2011, 14:54:38 »
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    I'm new to CHDK and can't believe how awesome it is!  I love doing timelapse videos and CHDK really opens the possibilities for timelapse on canon point and shoots.

    What would be perfect is a script that shoots timelapse in continuous mode like this one

    http://chdk.wikia.com/wiki/UBASIC/Scripts:_A_fast_%22intervalometer%22

    but also repeats a bracketing function over and over.  The idea is for it to never leave the continuous mode.  I would personally use it to shoot one long exposure followed directly by one very short exposure (to capture the highlights of the scene).  Is there anything out there that can do this.  Again, I want it to continuously shoot one long then one short exposure repeatedly for as long as I run the script.

    Using ultra intervalometer script and CHDK bracketing in continuous mode in TV set to 3 or 4 EV and my self timer set to delay=0 Shots=2 gets me the result I want except it is slower than shooting in continuous mode and is not as consistent in the interval because sometimes the camera isn't ready for the next shot.

    Any tips or ideas would be very much appreciated.  Thanks.

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    Offline fudgey

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    Re: Continuous shooting repeat bracketing
    « Reply #1 on: 07 / July / 2011, 18:14:22 »
    This is something that would IMO be best and easiest done in CHDK C code, adding yet another continuous mode bracketing parameter to control after how many shots to reset the bracketing to its original value. I think I've once suggested/requested this feature (from myself, at least :P).

    It may be possible to do this in scripts even without modifications to CHDK (continuous mode bracketing disabled), by fiddling with propcases while monitoring the shooting process in a tight loop but it sounds more complicated and less reliable/portable to me.


    But do note that continuous mode interval is not consistent. For example with my camera SD card write slows down when enough files appear on the card. To fix that I once thought about adding a scriptable delay feature somewhere in the shooting code already tapped by CHDK, to slow down continuous mode down to a frame rate that the camera can keep up with eternally.

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    Re: Continuous shooting repeat bracketing
    « Reply #2 on: 08 / July / 2011, 04:13:13 »
    Thanks for the reply.  I would be very interested to see a bracketing reset feature like you mentioned.  Maybe I should learn to program :)

    I understand that continuous mode interval is not consistent, but depending on my shutter speed and interval it seems to be a better option for me than ultra intervalometer.  A "normal" shutter speed for a film camera is half the time of the interval between frames.  24fps is the standard film format (each frame is 1/24th of a second long) and the typical shutter speed is 1/48 of a second.  When I shoot timelapses with a long interval (e.g. 3-5 seconds) and a short shutter speed (let's say 1/120), motion appears jumpy and there is no motion blur that we're used to seeing in films.  My goal when shooting timelapse is to get close to the 180 degree shutter standard that they use in film.  I go for longer exposure like 2 seconds for an interval of 4 seconds.  This generally requires additional ND filters, but gives a more natural, less strobic feel and doesn't seem to require much if any deflicker in post because your exposures are more of an average of the light in the scene instead of a 1/1000 of a second sample.  Anyways, long story short the continuous mode seems to be very consistent when I use longer shutter speeds.  I do not experience a slow down when the buffer fills because it seems to have enough time to keep up.

    I have decent control over the interval by setting the shutter, though if anyone knows an intervalometer script that can consistently shoot a 1 1/3 second exposure with a 3 second interval on the g12, I'd be very happy with that.

    I'm sure nobody's actually read this far into my post, but I'm just excited about the possibilities of CDHK and the idea behind quickly and consistently shooting one long exposure followed by one fast exposure is to expand the dynamic range of these cameras while also maintaining the smooth motion blur that we are used to seeing in most films.  The new Red Epic cameras have an HDRx mode that cleverly takes one normal speed exposure (e.g. 1/48 for 24p) and one fast exposure (3-6 stops faster) at the exact same time.  Later in post you can combine these into one video with 3-6 stops more dynamic range than the native sensor is capable of.  They do this less for extreme tone-mapping and more for a natural blend of the 2 images that preserves the highlights.  I doubt it's possible to get 2 different exposures from the same image in a Canon point and shoot (for now), but having a way to shoot one normal exposure and one fast for highlights would be the next best thing to Red's HDRx mode.  For timelapse it would basically be as good.  Again, sorry for the long post but realizing your $450 Canon camera has more potential for professional use than it has any right to is a pretty exciting thing.

    Full on HDR timelapses are really cool and have their place, but when you need a smooth look with a more filmic motion blur you really need an exposure that's around half of your interval time.

    What do you think?  Have I just not found the right intervalometer script yet?

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    Offline fudgey

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    Re: Continuous shooting repeat bracketing
    « Reply #3 on: 09 / July / 2011, 04:54:28 »
    I do not experience a slow down when the buffer fills because it seems to have enough time to keep up.

    Just to clarify this a bit: these cameras don't have buffers like DSLRs. The slowdown I was referring to doesn't happen until ...umm... let's say 2000 frames have been shot (I don't remember exactly but 2000 is where each new xxxCANON directory is created after numbering reset). It probably has something to do with how the camera handles the SD card file system, photo indexing or whatever.

    What do you think?  Have I just not found the right intervalometer script yet?

    Any decent intervalometer script uses get_tick_count to allow (near) exactly correct frame rate and of course allow you to use manual Tv. But they can't make the camera go faster when preparing for the next shot. So if your camera needs (always or in some lighting conditions) more time to write a JPEG, enable sensor, go through focus & exposure (even if all set in manual it takes more time than in continuous mode as you've noticed), then there's nothing a script can do to help.

    Except for one thing... you can achieve continuous mode shooting speed (or at least go near that) in scripts by simulating keypresses according to the camera's feature where you can use the same focus & exposure settings for several shots in your own rythm by repeatedly pressing the shutter without releasing half-shutter in between shots:

    - press "shoot_half"
    - wait for exposure, set overrides or whatever necessary

    repeat
    - click "shoot_full"
    - wait for the shot
    - optionally adjust exposure
    until until you want to stop the timelapse, then

    - release "shoot_half"


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    Offline fudgey

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    Re: Continuous shooting repeat bracketing
    « Reply #4 on: 10 / July / 2011, 13:23:38 »
    Except for one thing... you can achieve continuous mode shooting speed (or at least go near that) in scripts by simulating keypresses according to the camera's feature where you can use the same focus & exposure settings for several shots in your own rythm by repeatedly pressing the shutter without releasing half-shutter in between shots:
    Oops, turns out you actually can't because of http://chdk.setepontos.com/index.php?topic=1444.msg13111#msg13111 (unless it's been fixed since the older build I had in my cam when I tried it).

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    Re: Continuous shooting repeat bracketing
    « Reply #5 on: 10 / July / 2011, 14:09:20 »

    What would be perfect is a script that shoots timelapse in continuous mode like this one

    http://chdk.wikia.com/wiki/UBASIC/Scripts:_A_fast_%22intervalometer%22

    but also repeats a bracketing function over and over. 

    Check the following and see if it does what you want :-

    http://stereo.jpn.org/eng/sdm/tlapse.htm
    http://stereo.jpn.org/eng/sdm/tlapse2.htm

    You can do TV bracketing, focus bracketing from current focus to infinity and even focus bracketing combined with Tv bracketing.

    You can bracket continuously if you set a suitable interval.
    Because of many factors you can never force a bracketing rate similar to the cameras continuous-shooting speed.
    You will have to settle for less but the above will certainly do it.

    All the 'heavy lifting' is in the 'C' code.


    David

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    Re: Continuous shooting repeat bracketing
    « Reply #6 on: 14 / July / 2011, 04:36:51 »
    I haven't been on here in a few days.  Thanks for the responses.  Fudgey, I didn't realize these cameras don't actually have dslr style buffers.  I know sometimes my camera skips a beat while shooting in continuous mode with a slower SD card.  I'll watch out for the slow-down that you described.  Sounds like it shouldn't affect too many of my timelapses.

    Microfunguy,  thanks for the links.  Very useful information.  I have found that nothing is as fast as the continuous shooting mode, and because of my style of shooting timelapse photography, I'll be shooting in continuous for most of my shots.  I would love to be able to shoot a quick extra frame inbetween each longer exposure for my highlights, but the overall motion of the finished film is more important to me.  So for now, I don't think I'll bracket most scenes, unless there is little to no motion happening, e.g. a timelapse of a shadow changing throughout the day.

    I'm really loving CHDK.  It's opened up so much in these little cameras!

    Here's some TL footage from my first evening out with the G12.  Click through and watch in HD.

    http://www.youtube.com/watch?v=NIk8XCk79iA#
    « Last Edit: 14 / July / 2011, 04:38:49 by andy_chdk »

     

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