55D / T2i - disable preflash

[ghostgeek]

I saw a thread about this subject from a few years back, but the thread died.

http://www.magiclantern.fm/forum/index.php?topic=1299.0

To recap, others had requested a feature to disable the "preflash" that the 550D / T2i fires from it's built-in popup flash.

This is a problem for those of us that use inexpensive optical strobes that are triggered by another camera flash.   The camera's built-in flash is stuck in E-TTL, which produces a "preflash" prior to the image being exposed.  This preflash triggers dumb optical slaves, rendering them useless.  This feature is apparently impossible to override in the default camera settings, and has thus far not appeared in ML. 

The only practical way to trigger optical slaves  is to use the lock exposure FEL.  In other words, manually fire the pre flash using the * button in advance of the main flash.  Then give the slaves (and of course the built-in camera flash) 10 seconds or so to recharge before taking the photo.  It WORKS, but is not ideal as it requires the photographer to wait for the strobes to recharge.

On the other thread, some users remarked that the preflash is "impossible" to override - even in ML.  But why?  ML is able to take photos in "video" mode, but I note that the built in flash does not fire in this mode.  Could the built in flash not be triggered to fire when taking a photo in live view video mode in ML?