rjans Posted November 21, 2010 Share #1 Posted November 21, 2010 Advertisement (gone after registration) My CM is default sett to flash off but from time to time I need the flash. At this moment I am using a 400 ISO film. The SF-24 D flash indicates a flash range of 16 meters at f 2.4. I have been thinking of using a Portra 800 ISO in the near future. The question regards the flash range: can I double the distance so I end up somewhere at 32 meters? Thanks Best Roger Link to post Share on other sites More sharing options...
Advertisement Posted November 21, 2010 Posted November 21, 2010 Hi rjans, Take a look here CM plus SF-24 D flash range at ISO 800?. I'm sure you'll find what you were looking for!
masjah Posted November 21, 2010 Share #2 Posted November 21, 2010 My CM is default sett to flash off but from time to time I need the flash. At this moment I am using a 400 ISO film. The SF-24 D flash indicates a flash range of 16 meters at f 2.4.I have been thinking of using a Portra 800 ISO in the near future. The question regards the flash range: can I double the distance so I end up somewhere at 32 meters? Thanks Best Roger No, you would get 1.4 times the distance (square root of 2 actually). Link to post Share on other sites More sharing options...
rjans Posted November 21, 2010 Author Share #3 Posted November 21, 2010 Thanks John, I was not aware of the formula. So it will be around 22-23 meters. That's far enough. Best Roger Link to post Share on other sites More sharing options...
pico Posted November 21, 2010 Share #4 Posted November 21, 2010 Thanks John, I was not aware of the formula. So it will be around 22-23 meters. That's far enough. I wonder if the original specification presumes the flash's Fresnel lens is in place. Flash can seem counter-intuitive at first. Here's a question. Let's presume flash-bulbs here so we don't have to buy a bunch of electronic units. If one bulb gives an adequate exposure, but you want to stop down four more stops and maintain adequate exposure, then how many bulbs will you have to pop? 2? 4? 8? 16? (I am using multiple flashes rather than one flash multiple times to avoid the arguments regarding iterative exposure.) Oh, if you want to REALLY light up an area, use the unit above. It uses Mazda/Edison-base flash bulbs. I have four than all be lit at once. Link to post Share on other sites More sharing options...
masjah Posted November 21, 2010 Share #5 Posted November 21, 2010 16 I should think? Link to post Share on other sites More sharing options...
rob_x2004 Posted November 21, 2010 Share #6 Posted November 21, 2010 Stand closer. The bulb only has the power it has. Link to post Share on other sites More sharing options...
pico Posted November 22, 2010 Share #7 Posted November 22, 2010 Advertisement (gone after registration) Stand closer. The bulb only has the power it has. Tell that to O. Winston Link. See his lighting kit here. I will leave it to the reader to surf out his work. Answer is 8. Link to post Share on other sites More sharing options...
budrichard Posted November 22, 2010 Share #8 Posted November 22, 2010 16. Work it out. Each f stop is 1/2 the light and that is 1/2 to the 4th power or 1/16. Or starting with one bulb, one stop requires twice the light or 2 bulbs, Another stop requires twice the light or 4 bulbs. Another stop requires twice the light or 8 bubs and finally 16 bulbs.-Dick BTW just set the ASA you want with the appropriate reflector on the SF24D, f stop and the flash will tell you the range in either feet or meters. Link to post Share on other sites More sharing options...
pico Posted November 22, 2010 Share #9 Posted November 22, 2010 16 bulbs I forgot to count to four. Me Gosh, a fractional underexposure! Is my face red! There's an outfit online that wants $5USD per bulb (Mazda/Edison based). What's he smoking? Link to post Share on other sites More sharing options...
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