5D2 Bulb Exposure - Shutter Press to Start and again to Stop

[cempey]

Is there a way on the 5D2 to have a shutter press start and exposure then a second shutter press stop the exposure.    I am trying to do some long exposure light painting where I will not be at the camera and will be triggering the camera with a set of pocket wizards.    This is traditionally called T Mode I believe but not available on the 5D2 stock firmware. I have not been able to find an option for the at in the latest nightly build of ML and haven't found an answer when searching the forums.

[reddeercity]

Have you check in to Dual ISO FRSP (Full Res Silent Picture) , not sure if that's what your after . I'm not a photographer , I'm a Video Guy .
You set dual iso to a base of e.g. 100 iso & then the second iso or (recovery ISO) to 800 iso
which end up as a 20bit HDR 14+ stops on the 5D2 .

But it's not really lengthening the exposure , One last thing
You can try my crop_rec  FLV (1:1 pixel 5632x3124 @ 3.8fps)
I can also make a special super low frame rate .5-1fps in full res (5632x3752) if there's enough interest .

I'm not even sure if dual exposure is possible on 5D2
Edit: found this
can-you-do-multiple-exposures-with-the-5d-mark-ii
hjoseph7, Jun 19, 2009 wrote

Actually you can do double exposure with any Digital camera, but there is a trick to it.
It must be done in complete darkness and the shutter must be left open using the bulb function.
Once that is set up, you can use flash to illuminate a subject, move the subject around and use flash to illuminate it again.
When you close the shutter. Two different images will be recorded on the sensor.

Never tried it myself so not sure on the results

Canon CPN says multiple_exposure_shooting

However, the Canon EOS-1D X Mark II, EOS 6D and EOS 5D Mark III DSLRs feature multiple exposure stacking of between two and nine frames.

Ok after reading this have you tried Bracketing

HDR Bracketing
Exposure bracketing for HDR images and timelapses.
• In M mode, this function does shutter and/or ISO bracketing. In the other modes it does
exposure compensation bracketing.
• To start bracketing, take only the first picture and ML will continue the sequence.
• To preview HDR images in camera, set SET+MainDial: ExposureFusion from Prefs menu,
Image review settings, then go to playback mode, hold SET and turn the main dial
(wheel).
• For each HDR picture set, Magic Lantern may also write a bash script for stacking the
exposures with enfuse (version 4.x), with optional alignment (align_image_stack).

[cempey]

Thanks but I am not looking for HDR or Bracketing.  I need to be able to control exposure start and stop remotely.  Exposure times are variable based upon however long my light painting takes.  May be 30 seconds, or it may be 2 minutes.    With a Pocket wizard in hand, I want to be able to trigger the camera to start the exposure (a 2nd Pocket Wizard with a camera remote cord connected to the camera is the receiver). Once I have completed my exposure, a 2nd press of the shutter through the Pocket Wizard should stop the exposure.

[Walter Schulz]

Don't own a PocketWizard and therefore unable to test it.
Is your device able to actuate shutter trigger for about 1.5 seconds?

[cempey]

Yes it can.  The PW is acting like a wired remote without the locking mechanism.

[Walter Schulz]

Fine! All you have to do is to use an adapter. Can be done by taking a cheapo wired trigger with an N3 connector + some solid wires + Sugru. Create a N3 male connector using wires and sugru. Now connect Shutter output to Focus input.
Now your trigger will actuate Half-Shutter (=Focus) which will start bulb exposure after 1 second.
By triggering Half-Shutter again bulb exposure will be stopped.

[cempey]

Thanks.  I found out that the Canon RC1 and the newer RC6 remote shutter releases can both operate in this mode when using bulb.