If you're using P-TTL, then you're at the mercy of however the metering/exposure system in the camera is programmed. Unless you're taking test shots of a uniform subject (such as a plain white wall) you may find you're running foul of some heuristic that's trying to compensate for combined flash & ambient light.
It was rumoured that the PZ-1p made some use of focus distance in calculating flash exposure, and that was well before P-TTL came along. I would not be at all surprised to find that the algorithms used in the modern digital bodies can result in non- linear behaviour under certain circumstances. Or, of course, you may have a hardware problem; we'll see if others can reproduce your problem with similar gear setups. On Fri, Jul 10, 2009 at 10:10:23PM +0200, AlunFoto wrote: > John, > You describe how I would expect the flash to function. My observation > was that at _one_ particular zoom setting, 48mm, the output is two > stops brighter than any other zoom setting. This also includes 58mm > which, as you say, should produce a more concentrated beam. If there > was any logic to this the 58mm zoom setting should have been even > worse than 48mm, but the histogram at 58mm is perfect... :-( > > Jostein > > 2009/7/10 John Francis <[email protected]>: > > The flash doesn't have more power output when zoomed, but it does > > concentrate the flash output in a smaller field of illumination. > > This means that an object will receive more illumination when the > > flash is zoomed in. ?If you're getting close to being within the > > minimum distance, you may well find that the flash cannot quench > > fast enough to avoid blowing out the exposure. > > > > Notice that the Guide Number for the flash depends on the zoom > > setting - from the table on p82 of the manual you can see that > > the guide number varies significantly as the head is zoomed. > > > > > > -- > > PDML Pentax-Discuss Mail List > > [email protected] > > http://pdml.net/mailman/listinfo/pdml_pdml.net > > to UNSUBSCRIBE from the PDML, please visit the link directly above and > > follow the directions. > > > > > > -- > http://www.alunfoto.no/galleri/ > http://alunfoto.blogspot.com > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
