Helen Bach
(K=2331) - Comment Date 10/27/2005
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Hi Justin,
Remember that the flash synch speed for your shutter is not the equivalent 'shutter speed' of your flash. 1/250 is probably the shortest shutter speed for your camera that has the entire frame uncovered at once (ie the first curtain has fully opened and the second curtain has not begun to close.
The actual shutter speed can be much less than this - in fact few electronic flashes last as long as 1/250 sec. Most flash units control their output by controlling the duration of the flash. If you have a flashgun with a manual power setting, set it to the least power - the flash duration could be 1/10,000 sec. If your flash gun only has auto, then use it close to the subject with as wide an aperture and as fast a film as possible - taking image quality and the capability of your flashgun into account.
You may not need to trigger the shutter if you can take the photo in complete darkness - set a long shutter speed, then trigger the flash when you want the photo taken. That might be easier to arrange, and have a shorter lag, than triggering the camera.
Best,
Helen
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David Hofmann
(K=22223) - Comment Date 10/28/2005
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Hi Justin,
electronic flashes, the ones you get for todays cameras, have a very short flash time. The so called flash sync time of a camera doesn't say anthing. Its the time of the actual flash. The actual flash time is between 1/500 to aprox 1/25000. Unlike a light bulb, an electronic flash can't be dimmed. To get less intensity, the flash fires for a shorter time. If your flash allows to set its output power, try setting it to the lowest setting possible. That is the shortest flash time.
I did some experiments with bullets from an air gun, but could not freeze it. It works for bursting baloos, though.
To trigger the flash there are a couple of simple electronic triggers available. Just look through the catalog of some good photo stores.
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Justin Campbell
(K=1398) - Comment Date 10/28/2005
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Thank you letting me know helen. I had no idea that the shutter time had little relevance to my flash time. Do you know if it has always been this way? Where can i find out the actual time of the flash. This seems like an important thing to know in figuring out equations of the object being photograph's speed and the light speed.
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Justin Campbell
(K=1398) - Comment Date 10/28/2005
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Could you not freeze the bullet because your fingers weren't quick enough or the flash duration was too long?
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David Hofmann
(K=22223) - Comment Date 10/29/2005
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the bullet was too fast, it was blurred even though it was only an air gun. A real bullet is way faster.
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Timothy Yap
(K=997) - Comment Date 10/29/2005
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Justin, goodluck with this - seems like a big project. I think that to effectively catch a bullet a highly specialised (and therefore expensive) set up is required - not only with flash but also camera. Interested to see if you can pull it off, but fairly sure you will need big $$$. Goodluck.
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Timothy Yap
(K=997) - Comment Date 10/29/2005
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http://www.rit.edu/~andpph/text-agfa-1280-hs.html
is an interesting link documenting an attempt at capturing a .22 calibre bullet. (States the required exposure time to be ~1/1,000,000 second). Although his camera is well outdated, some of the problems he encounters could be useful to you. have fun...
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Helen Bach
(K=2331) - Comment Date 10/30/2005
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Justin,
The minimum flash duration will depend on your unit - for example the Vivitar 283 can be controlled so that it will give a 1/30,000 sec flash which won't freeze a bullet perfectly, but it will make it visible and a little blurred, depending on the bullet velocity. Try searching the web for info. In general flashes have a minimum duration between 1/10,000 and 1/30,000 sec, with most around the 1/25,000 mark.
The relationship between shutter speed and flash duration has always been like this for electronic flash. Flash bulbs (ie the ones filled with magnesium foil or wire that can only be used once) are different - they last much longer, particularly the 'FP' (focal plane) type.
Best,
Helen
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stuart kennedy
(K=172) - Comment Date 10/31/2005
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I was my understanding that you would need a shutter speed of 1/4000 to 1/5000 to freeze a bullet. I beleive thats what my photograhpy teacher told us. Mind you that was about 3 years ago, so, don't hold me to it.
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Bad Site
(K=979) - Comment Date 10/31/2005
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"....need a shutter speed of 1/4000 to 1/5000 to freeze a bullet"
Its not the shutter that freezes the bullet but the duration of the flash. The trick is triggering the flash as the bullet passes by, that is the key to high speed photography. There are lots of info on the web for HS photography, do a google search.
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