pensive tomato said:
1) Do you see any benefits of using the omni-bounce on the MT-24EX? I think it's there in your setup, but I wonder about its effectiveness taking into account the suggested use of the omni-bounce versus the nature of macro lighting.
2) I really like the idea of the extension bracket for background light. Have you experienced any problems with line-of-sight contact getting the flash to fire?
3) I've been tempted by the MP-E 65mm for a while. Do you use the use Canon's hood on it? If so, what's your experience, particularly if attaching the MT-24 EX directly to the lens with the ring adapter?
1) Benefits are probably minor in terms of direct light on the subject. Relative to the size of the subject at the distance from the flash heads, even the small heads of the MT-24EX as bare flash are like taking a portrait of a person with a 6-foot softbox - you're going to get soft light regardless. But the diffusers do throw a little but of that light in other directions, which can be helpful.
2) I haven't had any issues triggering the slave 600 using the MT-24EX as an optical master. You do need to make sure the slave sensor (the black 'window' above red panel for the AF assist lamp on the flash) is not pointed completely away from the twin flash. I wonder if having the StoFen diffusers throwing some light around from the twin flash heads actually helps there, particularly with non-reflective subjects?
3) I have Canon's little hood for it…I use it when I've got the twin flash heads on the Wimberley F-2 brackets, but not when I'm mounting the flash directly to the lens. The reason for that is that I use a filter (B+W MRC) on the lens. Without getting into a whole debate on protection value vs. IQ of filters, I'll say that with the extremely short working distance of the MP-E 65 at high mag, with that lens in particular things are likely to come into contact with the front element (despite it's small size). I'm often shoving the front of the lens into bushes, so the hood wouldn't offer too much protection. As you may be aware, the twin flash can mount directly onto the lens barrel, and the hood can be screwed into the filter threads at the end of the barrel. But, if you put a clear/UV filter on the threads, you can no longer mount the twin flash holder ring directly to the barrel. Instead, I use a Macrolite 58C adapter (normally used to mount the twin flash to a 58mm-threaded lens without the ridge for it, like the old 100mm non-USM macro or a PowerShot G-series). The adapter screws onto the front threads of the UV filter, and the flash mounts to that. However, the Macrolite adapter doesn't have threads for the little hood. So, given the choice between the limited protection offered by the hood but direct flash mounting vs. good protection with a filter but no hood with direct flash mounting, I chose the latter.
Hope that helps...