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 Bulb-ramping for the "Holy Grail" win? - Day to Night 
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Post Bulb-ramping for the "Holy Grail" win? - Day to Night
I finally decided to bring mediocrity to Vimeo in the form of two bulb-ramping timelapse tests. After that there is a (lengthy) video diary of the gadget and its basic operation, so don't feel obliged to watch beyond the first minute, unless you're a geek.

http://www.vimeo.com/7663437

Sadly I wasn't able to go any deeper than light pollution levels (some of which, shockingly, is probably from MILapse's house), nevertheless these tests span about 10 stops each. Seven or 8 stops of bulb ramping and another 2 or 3 stops from ISO ramping. The footage is straight-out-of-the-camera. Flicker is imperceptible except perhaps at the very shortest exposures, but even then...

I'm generally pleased with the technique/gadget, and I must say that it's a lot of fun. I don't know how you feel, but setting up a shot and 'hoping for the best' doesn't seem very satisfactory. Using bulb-ramping you actually participate in the time-lapse capturing process.

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Tue Nov 17, 2009 2:59 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
To use the Aussie vernacular -"that's bloody amazing" :-)

Is the < 33 in brackets> your total bulb/shoot time? ..... and not clear on what the < 0.3 with down pointing arrow> under the main time count represents...??

That's a sterling effort on the project.


Tue Nov 17, 2009 3:34 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
............ So, were you shooting 'batches' of 100 frames and adjusting you bulb ramp when you adjusted your ISO etc. ?
Does this mean you have to stop the shooting sequence when you do the previous adjustments or does the system keep shooting while all this is being processed?


Tue Nov 17, 2009 3:43 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
Do you see any post sunset light "bumps" yet? Where the amount of light perks up 10 minutes or so after sunset and then goes back down?

I thought it was my bulb ramping incorrectly (it ramped linearly and I had to guess a lot) that would cause a rise in the amount of blue light just after sunset - but now I even see it in a few of my shots where the exposure was fixed. I don't see it in your video. You can see it in the bay bridge day to night in "Another Cloud Reel" (ramped) and in the last shot in "the City Sleeps" (fixed).

Maybe it has something to do with the sun bouncing off the ocean/atmosphere after the sun drops below the horizon?

Ben

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Tue Nov 17, 2009 3:48 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
matt b wrote:
............ So, were you shooting 'batches' of 100 frames and adjusting you bulb ramp when you adjusted your ISO etc. ?
Does this mean you have to stop the shooting sequence when you do the previous adjustments or does the system keep shooting while all this is being processed?


Nothing has to stop, all changes can be done on-the-fly. This was very important, and actually tricky to achieve, since there's a lot of stuff going on. The gadget is now actually a dual microcontroller arrangement. One microcontroller (the master) does the user-interface (keypad+LCD), mathematics, keeps track of intervalometry etc. The other microcontroller (slave) receives instruction packets from the master (via I2C protocol), and its sole job is to do millisecond precision bulb-timing. Well, it also generates signals for the basic driving of stepper and servo motors. Up to 4 cameras can be independently controlled.

Code:
B=current_bulb_exposure_time  (33)       †3.0


The (33) is the shortest *controllable* bulb_exposure_time the camera can manage - measured in milliseconds. I'm using a 5DII here, the Rebel XT can't do shorter than 45ms bulb exposures. The good news is that the bulb mechanism can be timed to such high precision.

The †3.0 is the magical bulb ramp. The only reason I use 'per hundred' shots is because it's more intuitive/meaningful than saying '0.03 stops per shot'. Nothing has to stop, you can increase this bulb_ramp whenever you like. It can be changed in steps of 0.1 stops and you can also ramp the bulb_exposure_time down (the arrow becomes a down arrow). This is useful if you find that you're overexposing, or doing a nih-to-day time-lapse.

The rest is probably obvious.

Code:
I=Interval_remaining/Interval_set


and depending on whether you've set it to shoot unlimited shots or not

Code:
F=frames taken (up arrow) or frames left (down arrow)


The number that follows in parentheses is simply the length of timelapse footage accumulated thus far. A handy feature for the impatient.

Believe me, the menu system for this gadget is truly something to behold.

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Tue Nov 17, 2009 4:18 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
Delrious wrote:
Do you see any post sunset light "bumps" yet? Where the amount of light perks up 10 minutes or so after sunset and then goes back down?


I'm mostly seeing light pollution from the vicinity of MILapse's kitchen. I've only done seven tests, and six of the days were overcast. I'll keep a look out for the bump, though I don't think I'm seeing it. Perhaps you're capturing a high-altitude meteorological phenomenon.

I'm keeping a rudimentary log of the light-curves and at their fastest the light levels seem to drop at a rate of about 4 stops per 20 minutes. In case anyone's curious...

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Tue Nov 17, 2009 4:26 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
sorry bout that :oops: next time your shooting let me know so I can leave the light off for ya!

Looking great! Looking forward to seeing more...


Tue Nov 17, 2009 6:12 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
Very impressive. Thanks for sharing this.

So you are cutting the exposure time in half when you bump the ISO up by one stop? Couldn't this potentially be noticeable in the timelapse, as clouds and stars would change speed? Why not stick with, say, ISO 1600 to save yourself this trouble? Are the day exposures too fast for bulb?


Tue Nov 17, 2009 6:47 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
timescapes wrote:
So you are cutting the exposure time in half when you bump the ISO up by one stop? Couldn't this potentially be noticeable in the timelapse, as clouds and stars would change speed? Why not stick with, say, ISO 1600 to save yourself this trouble? Are the day exposures too fast for bulb?


In the first time-lapse I think I ramped the ISO from 100 to 800 and then back down to 200 - in one stop increments/decrements, and I didn't see any artifacts in the final image sequence. Of course, on the 5D you can do it with 1/3 stop increments, which would be even smoother, but more work. Things won't speed up because the interval is still the same, however the trail left by planes etc. will be longer/shorter. My greatest concern was having a sudden step in image noise, but the 5DII proved to be sufficiently noise-free.

Yes, if you want to end with deep night shots then the daylight exposures will be far too fast for bulb (if you kept ISO=1600). That's why I added the ISO ramping, so I could start earlier in the day at ISO=100. Ramp everything you can. You have roughly 12-14 stops to play with, and you can't go faster than 1/30s, that's the bottom line as far as bulb+ISO ramping is concerned. This is a very useful range, but not enough for mid-day to midnight.

Actually, because bulb exposures can be unlimited in length, bulb ramping can in principle give you endless stops; starting at 1/30s, after only 7stops you're talking about 3s exposures. If you can live with 30s exposures then bulb ramping can give you 10stops all by itself, and so on... If you want more stops (without ridiculously long exposures and intervals) then an additional aperture drive and/or vari-ND filter is still required. Another 7 or 8 stops would nail the Holy Grail problem. This may be a job for Tom Hanks.

The first table on this impressive page gives an idea of the stop-range required.
http://home.earthlink.net/~kitathome/LunarLight/moonlight_gallery/technique/LightAndCamera.htm

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Tue Nov 17, 2009 7:56 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
Wow, that's a great piece of work and really well thought out. Please keep us up-to-date on how you are getting along with this. I'm curious about the logs you are keeping of the light curves, do they follow the same curve from shoot to shoot, or do they vary depending on weather conditions? I'm guessing that if the light curves were consistant, then a formula for the curve could be applied to the bulb ramp.

Cheers - Andy

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Wed Nov 18, 2009 9:21 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
marshallarts wrote:
astronomerroyal wrote:
Its Achilles heel is the 1/30s shutter speed, which is what limits its useful range in stops.

It took me a few days to make it back to the forums. My apologies for the dumb question but could you explain this? Surely your camera can shoot faster than 1/30th. I must be missing something.

My one question on your design is: I assume you have to supervise the recording so that you can tell the machine to stop increasing exposure time, correct? This device wouldn't know to only increase exposure for a certain period of time as the sun goes down and then hold once it's dark would it? If not is there an explanation why that you've come to learn. For instance, when there is cloud cover along with light pollution would the exposure be different from a clear night so a device would need to adjust exposure in different amounts for these situations?


You have to use Bulb mode, which is really designed for ultra-long exposures. It's fundamentally different from other shooting modes, since it's the only mode in which the camera doesn't know beforehand when to close the shutter. Apparently there are timing overheads and reaction-times involved that limit the final exposure time to 1/30 - only Canon engineers can explain what's going on. To be honest I feel lucky that even 1/30s can be achieved.

As for automation, that's something Shutterdrone has covered with his 'external exposure control' project. Again, that's bulb mode, but he controls it with what is in effect an external light meter he built. That's my understanding at least. I believe Delrious has also done bulb ramping. Personally I'm not seeking full automation. Unless someone comes up with an amazing USB controller the best ramping timelapses will come from human supervision. For example, by looking at LCD I can easily tell when light pollution is starting to creep in - that's my cue to slow down the bulb ramping. It would require a very sophisticated controller to be able to make those sorts of predictive decisions.

There is a middle ground: building up a library of 'average light-curves' which can then be run again and again. By the way, the light-curves do change very much depending on the weather, light pollution, whether you're point East or West, and presumably time of year etc. Ultimately there will be some automation, but I suspect it won't be very satisfactory.

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Thu Nov 19, 2009 12:22 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
Hey Thomas,

reall well done!

That has soooo much potential!

Cheers

Murray


Fri Nov 20, 2009 12:04 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
Excellent results!

I notice that the manual shifting/linear ramping results in an interesting effect where during the transition period, you get a drop in overall exposure level, with a swift rise back up to roughly the same exposure level you had before the transition from day to night. Was that planned? Either way, it's a nice effect!

!c


Fri Nov 20, 2009 12:21 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
shutterdrone wrote:
I notice that the manual shifting/linear ramping results in an interesting effect where during the transition period, you get a drop in overall exposure level, with a swift rise back up to roughly the same exposure level you had before the transition from day to night. Was that planned? Either way, it's a nice effect!


No, that effect wasn't deliberate, just trying to change the ramp as little as possible, so as not to inject flicker. I have noticed that when you nail the bulb ramping so that the image is always normally exposed, you almost completely lose sense of the light levels changing. Not a very nice effect. It's currently overcast here in Ann Arbor - rather boring.

Murray Fredericks wrote:
Hey Thomas,
reall well done!
That has soooo much potential!


Thanks. When it comes to the mechanics of DSLR time-lapsing I think it's fair to say that there's a lot of room for improvement. I'm currently looking into molesting the camera via the USB socket, which might expand the possibilities a little.

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Fri Nov 20, 2009 12:59 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
Maybe we'll see the bulb/faster shutter speed capabilities in the future(faster than 1/30). I talked to one of Canon's head engineers about this problem and he said they might be able to address it in future cameras. No chance of getting a fix for the 5D2.


Thu Nov 26, 2009 12:42 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
I'd really like to see a built in "time lapse" priority mode on new cameras. Call it something different if they are concerned about people ruining shutters with doing too much time lapse. The camera has all it needs to do it's own metering and avoid harsh changes in exposure time similar to shutterdrones lightrails stuff, just a matter of them writing the software.

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Thu Nov 26, 2009 12:55 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
If we could find the right software engineer we could all get together and contract him/or her to write a software plug in. If we could contact a person who wrote code for the 5D2 that would be ideal. 20 of us could make it worth someones time.


Thu Nov 26, 2009 2:59 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
I bet my mom can write some software for it. she has been programming for 30 years. Not sure if I can get her to do it but it might be nice to come up with a list of things to include anyway.


Thu Nov 26, 2009 4:06 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
Would she be able to hack the canon software without turning it into a brick? That's the big question.


Thu Nov 26, 2009 4:56 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
Yes I'm sure she could but the company she works for owns everything she writes and at $100 an hour it might not be the best deal anyway. I just got off the phone with her. She told me I should learn to write in C but there is no way that is going to happen. I have another friend who spent a year reprogramming a dot matrix printer to play music so he might be up for it. As far as turning the camera into a brick goes I would think any responsible programmer would have a way to return it to its original state. How much do you think the person should be compensated? The cost may also include a 5d2 to play around with. Again it would be nice to have a list of things to add to this software.


Thu Nov 26, 2009 5:40 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
I'd be happy to chip in some dollars if it were possible. I assume you'd do a module within the Magic Lattern framework? http://magiclantern.wikia.com/wiki/Magi ... mware_Wiki

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Thu Nov 26, 2009 6:04 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
Thanks for that link, I passed it on to my friend. I also asked him what something like that might cost and I will let you all know. Ideally we would find an enthusiast with some time on their hands but it doesn't look like there are any in this forum.


Thu Nov 26, 2009 6:15 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
colinmlegg wrote:
I'd be happy to chip in some dollars if it were possible. I assume you'd do a module within the Magic Lattern framework? http://magiclantern.wikia.com/wiki/Magi ... mware_Wiki


that's crazy cool.

You could also petition Canon or Nikon for that matter for the usb sdk. They won't pass it over fast/easy but once your past that hurtle AND they decide to open more shutter speeds. Your in. I'm not holding my breath though.


Thu Nov 26, 2009 7:38 pm

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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
If enough people pitched in we could make it worth their time.

I'm seeing if I can find a canon guy to do it. For someone that knows the software it would probably be quite easy.


Thu Nov 26, 2009 8:51 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
My friend said he might be able to do it for 4000-10000. That estimate is just a guess though.

Ultimately having an intravalometer and some sort of bulb-ramping function is the goal? I was also thinking about the fact that my g10 has a ND filter function programed into it. It might be possible to put that function into the 5D2 and stop it down enough for midday to midnight.


Fri Nov 27, 2009 6:12 am
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
I'd want

ISO ramping
shutter ramping
Maybe a way to make the auto exposure settings only go one way. So it only goes up or down until reset

Both ISO and shutter with a way to control them through one of the ports or at the least have them work through the wheels on the camera.


Fri Nov 27, 2009 8:47 am
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
milapse wrote:
[You could also petition Canon or Nikon for that matter for the usb sdk. They won't pass it over fast/easy but once your past that hurtle AND they decide to open more shutter speeds. Your in. I'm not holding my breath though.


A couple of weeks ago I did this and (after some humiliation on their part) they sent me the download link. I didn't even have to lie. The SDK comes with sample code which compiled nicely in xcode (Mac). I'd say the SDK is moderately interesting, but doesn't obviously provide access to any camera functionality that addresses any big time-lapse issues.

Screenshot of the sample app, showing that the dork detection mode works quite well,

Attachment:
SDK_sample.jpg
SDK_sample.jpg [ 109.28 KiB | Viewed 14088 times ]


I opened up Interface Builder and messed around with the interface a bit to make it more time-lapse-esque. Didn't add any functional code though,

Attachment:
SDK_fantasy.jpg
SDK_fantasy.jpg [ 119.84 KiB | Viewed 14088 times ]


It might be quite handy to use as a tethered intervalometer for HDR shooting (something that bulb mode lacks the range for). I took a look at some of the source and in particular the shutter speeds. A snippet;

Code:
      @"125" , [NSNumber numberWithInt:0x70] ,
         @"160" , [NSNumber numberWithInt:0x73] ,
         @"180" , [NSNumber numberWithInt:0x74] ,
         @"200" , [NSNumber numberWithInt:0x75] ,
         @"250" , [NSNumber numberWithInt:0x78] ,
         @"320" , [NSNumber numberWithInt:0x7B] ,
         @"350" , [NSNumber numberWithInt:0x7C] ,


Not sure exactly what I'm looking at, but the "200" etc. are shutter speeds and the 0x75 etc. are hex code labels that the camera recognizes. Judging by the granularity of the hex values, and making some assumptions, it seems as though 1/8 stops is the finest shutter speed stepping you can get, although sometimes the steps are larger. Not exactly news. This suggests that the degree of flicker when using Av mode will be irregular. My guess is that the SDK doesn't reveal anything profoundly useful - that still requires the massive firmware attack.

That said, there might be something useful in there. For example, there's a DepthOfFieldPreviewOn/Off type command - perhaps it's possible to trap the lens in this mode, thus eliminating aperture flicker. Physically holding down the DOFpreview button on the camera doesn't work, but maybe software control is different ... There's also a BulbStart/Stop command (apropos to the subject of this thread), but I doubt it's an improvement over just doing it via the remote socket...

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Fri Nov 27, 2009 12:14 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
Dork detection...HA!

The ND filter on the g10 is a physical one :( so I guess that ruins my idea. I wonder with a little programming if someone could achieve lower ISOs. I don't understand why the ISOs can't go all the way down to 2, but I don't really understand much about this stuff in the first place. I know what happens at high ISOs but what happens at low ones?


Fri Nov 27, 2009 5:14 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
astronomerroyal wrote:
Judging by the granularity of the hex values, and making some assumptions, it seems as though 1/8 stops is the finest shutter speed stepping you can get, although sometimes the steps are larger.


1/8 would be quite an improvement over 1/3... If this stored the exif info as well you could implement the post filter pass we discussed yesterday ;)

Can you get a feeling for the ISO granularity as well?

Here's what might work:
-Standalone PTP controller (or laptop) that ramps 1/8 stops and coordinates iso. (the dof idea is interesting too)
-If the exif data is not stored there could be data models built or tracked/exported(?) based on iso,exp,F-stop
-Assuming raw there would be plenty of leeway to filter the steps out


Sat Nov 28, 2009 9:06 am
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
milapse wrote:
-Standalone controller (or laptop) that ramps 1/8 stops and coordinates iso.


Having given it some thought over the past few months I see three fairly distinct ways to attack the day-night issue:

1) Purely hardware. The bulb ramping as discussed in this thread = limited but smooth time-lapses achieved in-camera. Maybe supplement with other hardware like vari-ND and aperture drive.

2) A USB device using PTP control to squeeze the finest possible stepping performance out of camera (shutter,Aperture,ISO). This requires some hardware and some deflickering post-processing. I was under the impression that Canons already ramp in approx.1/8 stops when it's in Av mode, for example. The 1/3 stop granularity is just what the user is offered at the interface level. I think Flyvolm has demonstrated this in one of his videos. If this is true then there's no gain to be had from this option, and instead we consider option 3 ...

3) A purely post-processing method, 'exif extraction.' If I can resurrect my tests I'll start a separate thread about this method, but for now I'll just say that the camera is the controller, somewhat - if not totally - obviating option 2). No extra hardware is involved - it's pure software post-processing. Also, the method doesn't care about how big the exposure steps are - meaning that you can do staggered manual shoots and stitch them together later.

Then, of course, there's the option of rewriting the camera firmware, which only handful of people on this planet seem to be able to do.

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Sat Nov 28, 2009 11:41 am
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
According to canon the steppers in their lenses can only do a little less than a 1/3 of a stop. I thought about cutting open a lens and accessing the iris ring with an external stepper.


Sat Nov 28, 2009 6:49 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
Canon DSLRs do adjust both shutter speed and aperture in 1/8 EV steps. It's possible some lenses can only do ~1/3 EV steps, but the two lenses I happened to do the tests with - Canon 24mm f/1.4 and Sigma 20mm f/1.8 - both did 1/8 EV steps.

I thought of using exif for deflickering as well because MSU deflicker occasionally needed some help which I provided by adjusting exposure on individual frames in the sticky spots. I started writing a script to automate this in Perl, but could only find a rather poor tool for exposure adjustment (via ImageMagick) and figured that a Photoshop script would be the way to go. But now I'm using Graft deflicker which is more effective, and I'm getting the impression that what Graft can't fix it would probably be quite a challenge to write a script to fix.

Another issue with using exif is that it would work for Canons, but apparently not for Nikons. At least my D700 does not write accurate exposure data to exif: The exif data will stay constant when the exposure is clearly changing and vice versa. :evil: Other brands I don't know about.

What really needs to happen is that much smaller steps get implemented in firmware (shutter speed most importantly, possibly ISO too). I have written both Canon and Nikon to suggest this (along with suggestions for a practically useful in-camera intervalometer). Odds are that that was a waste of time, but you get nothing for not trying. I think that having a firmware hacker take a shot at it is more likely to bring about results. Frustrating considering how easy it would be for an inside firmware engineer to do it... :(

Until then, astronomerroyal's setup here is the most practical I have seen so far.

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Sat Nov 28, 2009 9:40 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
flyvholm wrote:
Canon DSLRs do adjust both shutter speed and aperture in 1/8 EV steps. It's possible some lenses can only do ~1/3 EV steps, but the two lenses I happened to do the tests with - Canon 24mm f/1.4 and Sigma 20mm f/1.8 - both did 1/8 EV steps.


Good, I was hoping you'd chip in. Do you think the steps are always 1/8 stops? I got the (admittedly weak) impression form the code that the steps are sometimes not as fine as 1/8stops.

flyvholm wrote:
I thought of using exif for deflickering as well because ...


Yes, I now remember you mentioning it. A time-lapse-friend of a time-lapse-friend apparently has written complete code (for 5D) that does exif deflickering from the bayer matrix. My very-trustworthy-and-not-easily-excited-time-lapse-friend said the results were 'quite impressive.' The code's being expanded to other RAW formats. This was also the case several months ago ...

flyvholm wrote:
Another issue with using exif is that it would work for Canons, but apparently not for Nikons. At least my D700 does not write accurate exposure data to exif: The exif data will stay constant when the exposure is clearly changing and vice versa. :evil: Other brands I don't know about.


Early on during my tests I saw something like this with my Canon 300D, but didn't understand what was going on. What I found that did work was using manual mode; one can only make steps that can be correctly reflected in exif. Touching the camera while shooting is not ideal, but I suppose it's another good excuse to (at least try to) put together a separate USB controller for changing T,A,ISO etc...

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Sun Nov 29, 2009 8:43 am
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
So we got a winner for timelapse novel prize, huh? :o

Pardon my ignorance but I wonder how you ramp ISO because I don't see ISO on your display pannel. Do you change ISO on camera? (Or I guess I have language problem, obviously... :( )

I keep coming back to see this thread again and again.... It is trully amazing.



[EDIT]

OK, I now found that you change ISO on camera between shots.
But now I wonder why you didn't control ISO and shutter speed together from your gadget?

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Fri Dec 04, 2009 12:34 am
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
astronomerroyal wrote:
Do you think the steps are always 1/8 stops? I got the (admittedly weak) impression form the code that the steps are sometimes not as fine as 1/8stops.

Yes, some of the steps are bigger than 1/8 EV and some are correspondingly smaller. I am pretty clueless as to why they made it this way.

astronomerroyal wrote:
A time-lapse-friend of a time-lapse-friend apparently has written complete code (for 5D) that does exif deflickering from the bayer matrix. My very-trustworthy-and-not-easily-excited-time-lapse-friend said the results were 'quite impressive.'

Sounds good; if done right a filter like that should be able to take care of most of the flicker. There's still shutter/aperture flicker that can't be accounted for this way, so a second run with a histogram-based deflicker filter may still be necessary in some cases.

astronomerroyal wrote:
flyvholm wrote:
Another issue with using exif is that it would work for Canons, but apparently not for Nikons. At least my D700 does not write accurate exposure data to exif: The exif data will stay constant when the exposure is clearly changing and vice versa. :evil: Other brands I don't know about.

Early on during my tests I saw something like this with my Canon 300D, but didn't understand what was going on.

Shutter/aperture flicker could possibly create variations when exif is constant, but something else is going on with my Nikon. Another "trap" is that exif values are commonly rounded. For Exiftool which I've used you'll only get rounded values unless you specify otherwise. I also have a 300D which was one of the cameras I used when testing, and I didn't notice any inconsistencies for that (or the 350D, 40D).

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Fri Dec 04, 2009 5:12 am
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
choi wrote:
But now I wonder why you didn't control ISO and shutter speed together from your gadget?


I control the camera via the 'external remote socket' or whatever its proper name is, not the USB socket. Currently all I can do is control the camera's bulb mode. I would love to be able to combine this with USB control so that I could do the ISO ramping via the gadget. It's a lot more complicated. I have the appropriate Canon code that could do this from a laptop, but I don't know how to program a microcontroller to do it. The protocol is called PTP and some people have already worked out the precise commands you have to send... but my gut tells me there are more enjoyable things to be done.

I'm a little suspicious of ISO ramping; sometimes it doesn't seem to work perfectly. Not sure if it's human error.

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Fri Dec 04, 2009 9:18 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
flyvholm wrote:
Sounds good; if done right a filter like that should be able to take care of most of the flicker. There's still shutter/aperture flicker that can't be accounted for this way, so a second run with a histogram-based deflicker filter may still be necessary in some cases.


From the outset I didn't worry about aperture/shutter flicker. I just added a routine at the end for deflickering that fluff. What drove me to despair was dealing with saturated pixels. Even to this day I feel a bit sick just thinking about them.

I just wish I were a stronger computer coder - `exif extraction/renormalization' would make a great After Effects plug-in.

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Fri Dec 04, 2009 9:35 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
OK.

I can guess that it's a lot more complicated.
But I don't understand you are suspicious about ISO ramping. From daylight to night sky, we are talking about from BDE ±0 stop to BDE -20 stop and there's no way(I guess) doing it without ISO ramping.

I use Nikon and I found some free 3rd party tethering programs. They are all able to control camera setting including ISO as well as aperture, shutter speed and white balance from a computer.

I guess what you meant was your gadget has different socket and that's why your current gadget is able to control only bulb. :?

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Fri Dec 04, 2009 9:36 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
choi wrote:
But I don't understand you are suspicious about ISO ramping. From daylight to night sky, we are talking about from BDE ±0 stop to BDE -20 stop and there's no way(I guess) doing it without ISO ramping.

I use Nikon and I found some free 3rd party tethering programs. They are all able to control camera setting including ISO as well as aperture, shutter speed and white balance from a computer.

I guess what you meant was your gadget has different socket and that's why your current gadget is able to control only bulb. :?


You'd think that halving the exposure time and doubling the ISO gives you exactly the same exposure, but I sometimes (not always) see a nasty step in the final footage. It might be my error, or the camera might be lying. I'd have to do some careful testing (v. boring). My estimate is that bulb ramping gives you about 7 stops to play with. Bulb + ISO ramping gives you 12 stops. Bulb + ISO + aperture ramping gives you about 18 stops.

I too can control my cameras from a computer, using `EOS Utility' software, but it can't control any of the camera settings smoothly. It really doesn't solve anything. Technically the computer can control bulb exposures (the only thing you can control smoothly), but even if you wrote a nice software package you'd have to carry a computer with you. I'd love to get all this functionality into a microcontroller gadget (a time-lapse equivalent of the `Promote Controller') but it's currently too complicated for me. USB = no thank you, sir.

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Fri Dec 04, 2009 10:06 pm
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Post Re: Bulb-ramping for the "Holy Grail" win? - Day to Night
astronomerroyal wrote:
The protocol is called PTP and some people have already worked out the precise commands you have to send...


You couldn't drop a link to what your talking about could you?

I'm interested in this EXIF / renormalization thing you are talking about... not really sure where its going, could you explain further?

One solution to this might be the same approach HDR takes... using a camera response curve you can effectively get the "radiance value", i.e. how much light was actually in the scene, and then you could use a ramping curve to remap the pictures into 8bit colour space (because the data would be based of radiance values instead of exposure settings you could effectively eliminate the flickering). I might just be talking out of my bum because I haven't really thought it through yet.

Cheers,
Dave.


Sun Dec 13, 2009 12:36 pm
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