On Fri, Jul 10, 2009 at 07:11:20PM +0200, AlunFoto wrote: > 2009/7/10 Bruce Dayton <[email protected]>: > > How did you happen to notice this behavior? > > Many of the DA lenses will focus closer than the recommended minimum > distance for the flash. I was going through how my various lenses > performed with the flash at close focus. This experiment turned out > quite well, in the sense that P-TTL copes with the short distances. > However when playing with the DA*16-50 I decided to check if it was > consistent across the zoom range of the lens. The flash was set for > auto zoom to match the zoom setting on the lens. That's when I got > overexposure on the long end. Same thing with DA 16-45/4. That's when > I switched to manual zoom and compared the flash output at each > setting. > > Jostein
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.
