On Thu, May 30, 2013 at 7:03 PM, Walt <ldott...@gmail.com> wrote: > On 5/30/2013 5:46 PM, Bob W wrote: >> >> On 30 May 2013, at 18:53, Walt <ldott...@gmail.com> wrote: >> >>> So, I was wondering where I might be able to learn more about shooting >>> manual flash in the event the TTL function fails me -- something to give me >>> an idea of when to adjust the flash output power, at what distances, etc. I >>> know nothing about guide numbers, flash modes, or anything like that. >>> >>> Anybody got any suggestions to that end? Any guidance would be >>> appreciated. >> >> The guide number tells you how powerful the flash. It's of no real >> consequence in practical shooting. >> >> To use flash manually, >> >> 0. Set the flash to manual >> >> 1. Set the ISO value on the scale on the flash >> >> 2. set the shutter speed to the flash sync speed, or lower >> >> 3. Measure the flash to subject distance - you should be able read this >> off the focus scale, but if you're bouncing the flash use the distance from >> the flash to the point on the ceiling, and double it. >> >> 4. On the flash scale, read off the correct aperture for the flash-subject >> distance >> >> 5. Set that aperture on your camera >> >> 6. Focus and shoot >> >> You can vary the flash output, eg for fill flash, by lying to it about the >> ISO. >> >> Setting the shutter speed slower than the flash sync speed gives you a bit >> of ambient light and some motion blur against the flash-frozen bit. >> >> B > > Thanks, Bob. > > Although, strangely enough, there's no ISO scale on the flash as far as I > can tell. None of the function buttons on the back seems to bring up any > indicators. I'll have to do a little digging around to see if there's > something I'm missing. > > Hmmm.
Nothing's missing, Walt. Modern flashes don't come with the exposure guide Bob described. I don't know when they stopped adding that, but I suspect whenever the fancy *-TTL flash automation became standard. Neither the Pentax AF540 or AF360 have it. The guide is also a simple mechanical thing and couldn't take into account the zoom setting in the flash head. The Guide Number is always quoted at full power at one particular zoom, eg 50mm, and it reduces as you zoom the head wider. If you set the flash manually to the same setting as the Guide Nimber is quoted for, eg ISO 100, zoom 50mm, then you can determine the aperture for a given distance from the subject with this formula: aperture = GN / distance -- -bmw -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
