Very odd issue with a Hassy 500C/M and an NPC polaroid back

[digic]

Hi all.

I'm currently experiencing a very strange issue:

I'm using a Hasselblad 500 C/M, an NPC polaroid back with Fuji FP-3000B, Pocketwizard TT1 and TT5 radios and Canon Speedlites.

I am fairly confident that I expose and meter properly, as this exposes correctly on roll film.

However; when using the polaback and the FP-3000B film, I get horribly underexposed shots. No idea why.
It's as if the flash isnt there at all. But this only happens with the polaroid film... Any thoughts?

Could the emulsion of the polaroid film be less suseptible to flash, or something (strange as it may sound)?

Thanks.

Realized this might be the wrong place for this, so if a mod would like to move this to the polaroid section that would be fine.

 

[johnielvis]

mystery--not enough light gets to the film..so you're obviously choking off light and don't see where--start opening up the lens maybe and see if the exposure improves....them speedlights I know nothing about but I'm pretty sure they are happiest with the camera that they're designed for...maybe they're choking off the light way faster than you think or are set wrong??? put a flash meter and check what light is actually getting out of them flashes--maybe one of the flashes is reflecting right in a flash metering senson--short circuiting the flashes??? pic of setup and pics may help

so an experiment--shoot in daylight or regular light--that film is fast enough for that type of regular room light--flash is way overkill unless you want teeny tiny apertures

I have used strobes with the 3000 speed and it works just fine for me by the way---regular ones and only after metering actual light output...no speed lights