[550D] Very long exposures in Bulb mode

[Alex]

I've just discovered how to trigger bulb mode from ML. Here is a test
build which allows long exposures up to 1 hour (not tested).

I've only tested exposures up to 80 seconds. For longer exposures, I
don't think it's necessary to disable power saving (camera already
does this while shutter is open). Not sure if extremely long exposure
times will have negative effects, so try this at your own risk.

To use, put the camera in Manual + Bulb mode, configure the timer
(between 1 and 3600 seconds) and use a remote trigger (either LCD
sensor or audio). It should also work with the intervalometer.

You can stop the long exposure at any time by half-pressing the shutter button.

[Carlos]

That's awesome Alex

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[Alex]

Fixed a small bug: changing the time with SET did not wrap around.

Also I've tried to implement trap focus without having to hold the
shutter; seems to work... sort of.

[Fernando Freire]

Wow!!!!. Genial, and intervalometer too. Astrophoto users are very glad, sure!!!

[Alex]

Now the question is: what's the resolution of the bulb timer? If it's
good enough, it could be used for timelapse with variable brightness,
with less flicker (less than 1/8EV).

On Wed, Jan 26, 2011 at 9:55 PM, Fernando Freire <nang...@gmail.com> wrote:
> Wow!!!!. Genial, and intervalometer too. Astrophoto users are very glad,
> sure!!!
>
>
>
>

[Fernando Freire]

Yes, I was precissely thinking about it. But suposse the favorable situation that we have a 1/32 resolution, on a range of exposures, not necesarilly all (perhaps between 1" and 5").

How I expect to use them to get a better timelapse?   The cam measurement is only 1/8 resolution, ...

perhaps if we done a subttle bracket of {-3/32, -2/32, -1/32, 0 1/32, 2/32, 3/32} EV for each timelapse shot and one external program chooses the right one to make a videoframe, based on minimize the variation of some parameter(s) (brightness?) of the previous images, or extrapolating it for the 3 or 4 previous frames...

... or choose the right one on cam an delete the remaining.

I don't know.


But I have some information, that could be useful: the mathematical relation between Tv and raw_shutter is

log2(1 / Tv) = ( raw_shutter-56 ) / 8

so, for raw_shutter = 56, we got 1/Tv= 2e0 = 1 => Tv = 1"

for raw_shutter = 32, we got 1/Tv = 2e-3 (exp base 2) = -1/8 => Tv = 8"

This will let us to assign raw values to bulb times at the same scale than other exposures of the cam

¿But if we have 1/32 resolution?

We need to extend by 4 the range of the cam and define

(1) ml_raw_shutter = canon_raw_shutter*4

so for 1":  ml_raw_shutter = 56*4 = 224, and


(2) log2(1 / Tv) = ( ml_raw_shutter - 224 ) / 32

and we have a method to operate (add, substract)  exposures 1/32 (bulb) and 1/8 (canon). Perhaps it could be also useful  to make HDR with bulb exposures.
 


 

[gart...@hotmail.com]

Hi Alex, I'm a newbie to the forums here, but man I have been awaiting
the D550 firmware for quite some time and after spending 4 hours
reading online threw all the build's last night I decided to give it a
go with the firmware on my camera, I found the latest build "jan26th"
and gave it a try because I was very interested in the BULB feature
and I saw you can go up to 1 hour (Very excited!)

I noticed one thing which was when you went to set the bulb time from
1 to 3600 seconds once you got to 3600 if you pressed the center
button to go back to 1 second it wouldn't let you. I'm at work so
cant try the "timer-2" build but did the "set wrap around" fix this
issue?

I have been dying to try some long exposures!

Thanks again for all your hard work, I'll for sure be donating to the
cause sometime soon here!!!!

THANKS! - Shawn M.

>  magiclantern-2011Jan26.550d.fw109.NoAudioMon.bulb-timer-2.alex.zip
> 1147KViewDownload
>
>  magiclantern-2011Jan26.550d.fw109.AudioMon.bulb-timer-2.alex.zip
> 1147KViewDownload

[Alex]

Yes, the timer-2 build fixes this issue.

Can you post some pictures taken in this mode? I wasn't able to test
it with the stars, as there's a lot of light pollution here. Thanks.

[gart...@hotmail.com]

Yeah, I was going to try it tonight, I will do a variety of different
times and post the results. Thanks again for all the hard work.

P.S. is there going to be any way in video mode for the camera to auto
focus while recording say if the camera is in focus on something and I
move it closer to the object it will be out of focus. Any way this
camera will be capable to keep the item in focus?

On Jan 27, 3:33 pm, Alex <broscutama...@gmail.com> wrote:
> Yes, the timer-2 build fixes this issue.
>
> Can you post some pictures taken in this mode? I wasn't able to test
> it with the stars, as there's a lot of light pollution here. Thanks.
>

> On Thu, Jan 27, 2011 at 9:58 PM, garth...@hotmail.com

[Shawn Malanaphy]

That's going to be something to advanced for me to give thought upon I can tell you that lol.

I'm really not familiar with what actually goes inside the firmware so I sorta don't have a clue on how that works :-(

Hoping a Genius like your self would be able to figure that out hahaha.

P.S. while I have you here, can you recommend any good add on mic's for this camera? I do more of motorsports shooting.

> From: broscu...@gmail.com
> Date: Thu, 27 Jan 2011 22:46:05 +0200
> Subject: Re: [ML] Re: [550D] Very long exposures in Bulb mode
> To: ml-d...@googlegroups.com
>
> With contrast detection AF, there's no way to know in which direction
> should the lens be rotated, or how much.
>
> Phase detection AF (which only works with mirror down) can tell
> (almost) exactly the direction and the amount of rotation needed.
>
> Focus peaking data can be used for a custom AF algorithm. I don't
> think it will be much better than Canon's, but at least it can be made
> not to hunt (i.e. just use a gradient descent).
>
> Thoughts?

[Ba...@aol.com]

 

P.S. while I have you here, can you recommend any good add on mic's for this camera? I do more of motorsports shooting.

 

Word is:  Even with Magic Lantern,   you still need to keep the level adjustments at the camera fairly low because the preamp in the camera is not considered very good.   As an early adopter of Magic Lantern,  I used the Juiced Link CX231,  which has its own preamp.   It also provide phantom power for mics that need it,  namely mics like the Rode NTG 3.     Coupled with a decent mic and low camera setting,   you can get pretty good sound.   Typically,   depending on the mic,  the recommendation was to put the left and right digital gains on the camera at 0,  and the analog gain around 10 or less,  if you can.

[gart...@hotmail.com]

Thanks for the reply, I have been looking at a Rode Videomic, since
they are somewhat smaller that some others and decently affordable and
have some good reviews.

[JaKoB]

wait for the new one coming out here soon 

http://www.rodemic.com/vmp/

[Alex]

I don't use any external mic, but I think I'll get one (to be mounted
on the flash hot-shoe).

Look around vimeo or youtube for audio tests with various microphones.
One of them is in the ML user guide.

[gart...@hotmail.com]

Nice, I couldn't find a expected release date, have you seen one?

[Ba...@aol.com]

Nice thing about motor sports is you don't really have to be concerned about getting enough sound.  Its usually,  how do you prevent clipping.  Last year I shot at the starting line of a drag strip,  and ended up hearing and feeling some the loudest sound I had ever heard. 

 

 

 

In a message dated 1/27/2011 1:17:41 P.M. Pacific Standard Time, gart...@hotmail.com writes:

Thanks for the reply, I have been looking at a Rode Videomic, since
they are somewhat smaller that some others and decently affordable and
have some good reviews.

On Jan 27, 4:14 pm, Ba...@aol.com wrote:
> P.S. while I have you here, can you recommend any good add on mic's  for
> this camera? I do more of motorsports shooting.
>

> Word is:  Even with Magic Lantern,    you still need to keep the level
> adjustments at the camera fairly low  because the preamp in the camera is not
> considered very good.   As an  early adopter of Magic Lantern,  I used the
> Juiced Link CX231,  which  has its own preamp.   It also provide phantom power
> for mics that need  it,  namely mics like the Rode NTG 3.     Coupled with a
>  decent mic and low camera setting,   you can get pretty good  sound.  
> Typically,   depending on the mic,  the  recommendation was to put the left and
> right digital gains on the camera at  0,  and the analog gain around 10 or
> less,  if you can.

[Lostfootage]

the Sennheiser shotgun mke 400 is a great shotgun mic for DSLR.


On Jan 27, 4:17 pm, "garth...@hotmail.com" <garth...@hotmail.com>
wrote:

[Alex]

With contrast detection AF, there's no way to know in which direction
should the lens be rotated, or how much.

Phase detection AF (which only works with mirror down) can tell
(almost) exactly the direction and the amount of rotation needed.

Focus peaking data can be used for a custom AF algorithm. I don't
think it will be much better than Canon's, but at least it can be made
not to hunt (i.e. just use a gradient descent).

Thoughts?

On Thu, Jan 27, 2011 at 10:38 PM, gart...@hotmail.com
<gart...@hotmail.com> wrote: