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Confused about flash bulbs

 
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JMP



Joined: 09 Oct 2006
Posts: 13
Location: London England

PostPosted: Mon May 14, 2007 8:52 pm    Post subject: Confused about flash bulbs Reply with quote

Hi,

I've just got my first Graflex - a Century Graphic. It came with a flashgun and the more I read about using flash bulbs the more confused I become.

It looks like I can get hold of #5, M2, M3, AG1 and AG3 bulbs.

The shutter on my lens is marked as M (10 and 25) F (50 and 100) and X (200).

I assume 1/200th can only be used with electronic flash but which of the bulbs would be used with M and which ones with F?

I'm thinking that if I'm stopping down to f16 I could shoot at 1/25 without worrying about ambient light creeping in - even in a normally lit room?

Finally, I read that Weegee used to use #5 bulbs at 1/200. Does the Speed Graphic synchronize with bulbs at a faster speed than the lens mounted leaf shutter? Also, I was under the impression that the bulb would burn for a lot longer than 1/200?

If anyone can give me some pointers, and clear up my confusion, I'd be grateful
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45PSS



Joined: 28 Sep 2001
Posts: 3209
Location: Mid Peninsula, Ca.

PostPosted: Mon May 14, 2007 10:58 pm    Post subject: Reply with quote

Have you read the Flashbulbs section located under the Technical Information heading on the home page?
Quote:
It looks like I can get hold of #5, M2, M3, AG1 and AG3 bulbs.

The numbers refer to the physical characteristics of the bulb. Which one you can use depends on the flash and adaptors that you have.
Quote:
The shutter on my lens is marked as M (10 and 25) F (50 and 100) and X (200).

M and F are types of flash bulbs, x is electronic flash. The numbers are suggested shutter speeds. As always slower shutter speeds can be used to include ambient light in the exposure, faster shutter speeds cut down the guide number of slower burning flash bulbs.
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Henry



Joined: 09 May 2001
Posts: 1439
Location: Allentown, Pennsylvania

PostPosted: Mon May 14, 2007 11:33 pm    Post subject: Reply with quote

The purpose of the M-F-X synch positions on your shutter is to match the shutter blades' wide open moment with the peak output moment of the bulb, each class of bulb having a different such moment. Forget about class F, they're for focal plane shutters which you don't have on your Century, nor are you likely to come across class F bulbs. You will be using M class bulbs (all those you listed plus some others, such as 5B, 25, 25B--B means blue, they're for use with color film), and they will all synch with the shutter speeds indicated for M class bulbs (1/10 and 1/25). The 5, the M2-M3, and the AG bulbs each have different bases, thus requiring different sockets in the flash unit. Chances are your flash will accept the 5, whose base/socket resembles an automotive bayonet-type although I think it's somewhat smaller, but without knowing exactly what flash you have I can't say for sure. There were flash units made with sockets that could be used for more than one type of bulb, and there were also adaptor sockets made that could be inserted into the flash to accommodate other bulb bases. Now you need to educate yourself about GUIDE NUMBERS in order to determine the proper f-stop, which is based on distance to your subject as well as the sensitivity of the film you're using (its ASA or ISO number, such as 64, 125, 200, etc.). Knowing the guide number for the bulb/film you're using, you divide it by the distance to your subject (in feet) to get the f-stop, e.g., with a guide number of 120 and a camera-to-subject distance of 8 feet, 8 into 120 = 15 (so f/16 would be close enough). It doesn't matter whether your shutter speed is set for 1/10 or 1/25 because it's really the duration of the flash that becomes your shutter speed, and this is mechanically synched to the shutter at its wide open moment, as explained before. Usually there was a table of guide numbers on the packaging that the bulb came in, or on the instruction sheet that came with the film (Kodak used to include such a sheet in each box of film, but that was in the good old days---sigh). Lacking those aids, the best source would be one of the Kodak Pocket Dataguides, which I own a couple of but these are long out of print. Let us know what film/bulb combo you're using and maybe we can come up with a guide number for you. HTH.
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JMP



Joined: 09 Oct 2006
Posts: 13
Location: London England

PostPosted: Tue May 15, 2007 5:06 am    Post subject: Reply with quote

Thanks guys for your help so far.,

The table under the #5 section (http://graflex.org/flash/ge-5.html) is incredibly useful and exactly what I need. Are there similar tables anywhere for M and AG bulbs?

However (and this is where I am confused) this table shows a GN of 240 for an EI of 80-125 at 1/50.

Whereas, the table printed on the back of a box of 5B bulbs says f8 at 20ft for 1/50 with Super Ansochrome Daylight film (which, according to info on the web was 100 ASA) so this gives a GN of 160.

Do different brands of the same bulb have different GNs?

My flash has a holder for #5 bulbs by default but also comes with the necessary adapters for M and AG bulbs. It also came with a package of M2 bulbs which give distance settings for different kinds of film but no aperture (do I assume f8?).

Lastly, much of the information I am finding is specific to different film types. Is there a handy table somewhere that shows all the various types of film with its speed?

Thanks again for your patience and any info you can give me.



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JMP



Joined: 09 Oct 2006
Posts: 13
Location: London England

PostPosted: Tue May 15, 2007 5:15 am    Post subject: Reply with quote

Henry wrote:
It doesn't matter whether your shutter speed is set for 1/10 or 1/25 because it's really the duration of the flash that becomes your shutter speed, and this is mechanically synched to the shutter at its wide open moment, as explained before.


This has also confused me a bit.

I know this is true for electronic flash but the table I was looking at here: http://graflex.org/flash/ge-5.html shows a different GN depending on your shutter speed.
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45PSS



Joined: 28 Sep 2001
Posts: 3209
Location: Mid Peninsula, Ca.

PostPosted: Tue May 15, 2007 8:00 am    Post subject: Reply with quote

Go back to the flashbulb technical page
http://www.graflex.org/flash/technical.html and try links flashbulbs http://www.graflex.org/flash/ then flash photography http://www.graflex.org/flash/navy/ then lastly from equipement recommendations http://www.graflex.org/flash/recommendations.html try the flashbulbs.com http://www.flashbulbs.com/index.shtml and look thru all the information provided there.

Quote:
Henry wrote:
It doesn't matter whether your shutter speed is set for 1/10 or 1/25 because it's really the duration of the flash that becomes your shutter speed, and this is mechanically synched to the shutter at its wide open moment, as explained before.


This has also confused me a bit.

I know this is true for electronic flash but the table I was looking at here: http://graflex.org/flash/ge-5.html shows a different GN depending on your shutter speed.


Flash bulbs work the same as electronic flash, only slower.
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Les



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

PostPosted: Tue May 15, 2007 11:14 am    Post subject: Reply with quote

There are two things different about flash bulbs over electronic flash. When it happens and how fast it happens.

If you looked at a time vs light output graph of most M class flash bulb you get a fairly gentle rise to a pretty broad peak with again a fairly gentle drop back to zero. The majority of light happens in around a 1/50 of a second. So if you set the shutter speed* to anything less, you'll get all of the light. Try to speed things up past 1/60 or 1/100 and things are going to look rather dim (thus, a lower guide number).

The same graph of electronic flash will have a a near vertical climb to a sharp peak and plumet back down. Most flash duration is shorter than the fastest shutter speed, so it really doesn't matter what speed you set your shutter, unless it's a focal plane shutter, but that's for a different post.

The other difference is when the light comes. With flash bulbs you are playing with fire, and it takes a little time for the fire to get started, for M class bulbs it's around 20 miliseconds (or a 1/5 of a second). So you have to send the voltage to the flash bulb 20 miliseconds before the shutter reaches peak in order to be synchronized. For early shutters that meant a solenoid attached to the shutter and constant fiddling with how slack it is. Later we got "fully syncronized" shutters internal timing circuts that had an extra lever at the side for 0,5,or 20 mil delay.

The Century shutter is a bit of an oddity. It uses different shutter speeds to control the delay that's why you need to sync M class bulbs at 1/25 while others with a Graphex or Supermatic shutter can sync the same bulbs at 1/60.
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clnfrd



Joined: 26 Mar 2002
Posts: 616
Location: Western Kentucky Lakes Area

PostPosted: Tue May 15, 2007 11:40 am    Post subject: Reply with quote

I'm pretty sure that that particular Century shutter doesn't have adjustable flash sync internally. It actually is set up to sync electronic flash which has zero delay. In other words, the shutter's internal switch closes at the instant the shutter is wide open. Because at 1/25th of a second the shutter is open for 40 milliseconds, it will sync with class M bulbs which reach their peak of illumination at around 20-25 milliseconds. Class F lamps are the gas-filled lamps (not focal-plane lamps) which reach their peak at approx. 5 milliseconds, so they will sync at those intermediate speeds because the shutter stays open for at least 5 milliseconds. So use electronic flash at 1/200th (or any of the other speeds, for that matter) but magnesium-filled Class M lamps such as 5's, 25's, 11's, 22's, Press 40's can only be used at 1/25th. Those smaller lamps such as M2's and M3's, etc., can probably be used at the F settings if you have an adapter to use them. Fred.
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