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Minimum safe distance for flashbulbs without a safety shield

 
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Stephen Furley



Joined: 11 May 2001
Posts: 79
Location: London, England

PostPosted: Sun Nov 23, 2008 8:08 pm    Post subject: Minimum safe distance for flashbulbs without a safety shield Reply with quote

I haven't had a lot of experience of larger flash bulbs, never dared to fire anything bigger than a No.5, and mainly used smaller ones. I have both 5 and 7 graflex reflectors, but have never used the 7. I've been trying to find something that would justify using flash, and think I've got a possible event coming up, a large group of people on stage at the Widescreen Festival at Bradford in March. This takes place in the Pictureville Cinema, part of the National Media Museum, previously the National Museum of Photography, Film and Television. On the Sunday morning everyone gathers on stage, and several people take photographs. It's mainly digital, with one or two 35mm, but since it's a photographic mueum I thought it might be appropriate to take the Speed Graphic next year. If I were to use the 7 reflector what is the minimum safe distance at whish itcould be used? Or should I just stick with the 5 reflector with it's safety shield? Distance will be about 20 metres from the stage. I'll have to write to the venue in advance to ask permission to use flashbulbs, and it might be easier to get if I can say that I'll be using a flash fitted with a safety shield.
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Les



Joined: 09 May 2001
Posts: 2682
Location: Detroit, MI

PostPosted: Sun Nov 23, 2008 10:16 pm    Post subject: Reply with quote

In all of my years using flash bulbs I've never had one shatter. the lacquer coating works very well. That said, I'd stick to name brand bulbs--sylvania, wabash, GE, etc rather than store brand.

Rather than the miniscule risk of fly glass, the bigger risk would be blinding people with a large bulb at close distances, for PRess 40s and No 11s I usually stick to 15 to 20 feet.

Now your situation (60ft) is at the ragged edge of single bulb photography.

Bill Cress's website shows with B&W 200 speed film, one press 40 will give about an f5.6. If I were restricted to on camera flash I'd want two of em to give me f8.

Even better would be a pair of No 2s or No3s in a largish reflector (smith victor type ) set off a couple of feet left and right of the camera.

No 2 would give about an F11.5 No 3s would be f16.
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glennfromwy



Joined: 29 Nov 2001
Posts: 903
Location: S.W. Wyoming

PostPosted: Tue Nov 25, 2008 1:21 am    Post subject: Reply with quote

At 60 feet from the subjects, I don't think there's any risk of injury from exploding bulbs. As stated, though, you're gong to need more than one to do the job. For remote reflectors you can use those clip on lights with the aluminum reflectors from the hardware store and use the extension plug(s) on your on camera flash. Regular household extension cords work for your off camera lights. You need to file the plug prong(s) down to fit the outlet on your flash gun, though. One, or both of the prongs will be smaller than modern cords.
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"Wyoming - Where everybody is somebody else's weirdo"
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Henry



Joined: 09 May 2001
Posts: 1443
Location: Allentown, Pennsylvania

PostPosted: Tue Nov 25, 2008 4:13 am    Post subject: Reply with quote

I agree with Les: not to worry! Never had a bulb shatter, ever. I think this was fear-mongering by Kodak to encourage purchase of their plastic baggy flash protector gizmo. Mind you, I speak only of the no. 5 (clear) and 5B (blue) flashbulbs in 5-inch reflector. YRMV.
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C. Henry



Joined: 13 Dec 2005
Posts: 359
Location: North East Georgia, USA

PostPosted: Tue Nov 25, 2008 3:20 pm    Post subject: Reply with quote

The only time I had any incident where the shield helped was with a #5/25 bulb of some brand other than Sylvania Blue Dot! The bulb did not shatter but it shot a stream of hot wire fragments out of a small hole that opened up in the bulb. This was instead of the expected flash of light.
For several years after that I would only use the Blue Dot bulbs and them only when the dot had not turned pink or purple.
I realize that this is no help with the question concerning big bulbs.

C. Henry
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robcruickshank



Joined: 25 Feb 2008
Posts: 19
Location: toronto, canada

PostPosted: Mon Dec 08, 2008 9:24 pm    Post subject: Reply with quote

I've never had a bulb burst either, but have found, based on a suggestion in the flashbulb group on Flickr, that the that the clear bags sold for roasting turkeys in, while a terrible idea for turkey, make good flash shields- they are completely transparent, very tough, and heat resistant. They tear easily, though, so you have to be a bit careful once you cut them.
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