In the old days, a tiny piece of "sun glass" would slide in in front of the flash sensor, when changing the aperture setting on the falsh unit to a smaller aperture (hole), thus indicating a different ISO value for a certain aperture (the one I wish to use, for instance) in order to delay cutting off the flash duration (changing the light out-put).
In advanced flash units, the "sun glass" has been replaced by an electronic adjustment of the flash sensor. Turning the disc on top of a Metz-45 or Metz-60 hammerhead unit actually changes the flash duration. I regret calling this changing ISO values, which is not exacly what it is, it's changing the suggested aperture - but if I stick to the aperture I will be using - I'll change the ISO setting acordingly. The result still remains the same: Less light for fill flash purposes, allowing me to expose the frame according to the ambient light rather than the (fill) flash. This is my suggestion for fill flash options, if your camera body doesn't offer this feature. Perhaps an other explanation is less complicated. Choose the apperture smaller (hole) than suggested by the flash unit. Set shutter according to the ambient light. Shoot! Enjoy the brilliant results of your photographs, that won't look much like flash photographs. BTW: I bougt my first Metz-45 in 1981 - and it still works exactly like the day I got it almos 25 years ago. Regards Jens Bladt Arkitekt MAA http://hjem.get2net.dk/bladt -----Oprindelig meddelelse----- Fra: P. J. Alling [mailto:[EMAIL PROTECTED] Sendt: 14. september 2005 17:09 Til: pentax-discuss@pdml.net Emne: Re: *ist D or DS & AF500FTZ for Weddings? The meter in the flash doesn't, with TTL flash the camera uses it's ISO information to decided when to quench the flash, and the flash, when using the flashes internal meter you set the proper aperture for the ISO and the flash just uses a formula. Jens Bladt wrote: >Well, if the ISO setting on the back doesn't have any effect on the >adjustments in the flash unit (if it's just a visual memory indication, as >suggested by you) the flash meter will not know when to cut off the flash >duration, will it? >Regards >Jens > >Jens Bladt >Arkitekt MAA >http://hjem.get2net.dk/bladt > > >-----Oprindelig meddelelse----- >Fra: Kostas Kavoussanakis [mailto:[EMAIL PROTECTED] >Sendt: 14. september 2005 12:18 >Til: pentax-discuss@pdml.net >Emne: RE: *ist D or DS & AF500FTZ for Weddings? > > >On Wed, 14 Sep 2005, Jens Bladt wrote: > > > >>I wonder how the flash actually DOES work, if the light output is >>indifferent to the ASA setting? >> >> > >The flash quenches when its sensor is happy. If your lens aperture and >distance were correct (indicated by the slider and thus affected by >the ISO setting), you are OK, if not, you are not OK :-) > >Or so I think. From Boj: > ><http://kmp.bdimitrov.de/technology/hot-shoe/index.html> > >"Automatic Flash > --------------- >An automatic flash is one that can limit the flash duration and >therefore the amount of light that it outputs. The control function >is performed by electronics contained inside the flash and guided by >a light-sensitive sensor located on the front of the flash. When the >sensor detects that enough light has returned back to the flash, the >control electronics terminate the flash discharge. In the simplest >flashes, the flash capacitor is shorted (so the extra charge is >lost), but in more advanced ones (those labeled thyristor), the >charge is preserved for the next flash discharge. > >An automatic flash achieves proper exposure not only when GN = d * F, >but also when GN > d * F. > >Automatic flash operation achieves correct exposures not only in >"straight-on" applications, but also when the flash head is tilted, >swiveled or covered with various gels and reflectors. To perform its >calculations, the flash assumes that some F (usually f/4 or f/5.6) is >selected on the lens. Failure to match F results in under- or >over-exposure. > >Program Flash >------------- >Pentax did not make any purely automatic flashes. Instead, they added >another feature, called "program flash," and gave the flashes in this >category the SA designation. > >Program flashes solve the problem of the photographer forgetting to >set the correct F before every flash exposure. When used in program >exposure mode, the flash and the body work together to set F. This >capability requires an extra contact, mode, so the flash can "tell" >the body what brightness it will produce. Knowing the film speed, the >body calculates and sets F. > >Some SA flashes have the extra functionality of signaling when proper >exposure was achieved. This is done either by lighting up a lamp on >the back of the flash or communicating with the body (via the ready >contact) and letting it make the flash symbol in the view-finder >blink." > > > >>For the reasons mentioned earlier, I harly ever use a flash in bright >>daylight. I know PJ's do it all the time. I never understood why. >> >> > >Contrast control. You get even illumination and remove the shadows >under the eyes. > > > >>I believe light looks better comming from above. >> >> > >I agree, it is softer and more diffused, but requires some direct >flash as well to eliminate the shadows. Thus the common "white card" >(or diffuser) trick. > >Kostas > > > > > -- When you're worried or in doubt, Run in circles, (scream and shout).
