Flash exposure with short shutter?

As I mentioned in another thread, I just discovered that with ISO 400

film, my lens set to f/18 (as small as the Argoflex goes), and the

wimpiest flashbulb I'm aware of, an AG-1B, I have to stand back about

twelve feet to take a properly exposed picture (which is also to say,

I got the battery, and found a suitable replacement for the dead

capacitor -- forty years or so in the original box killed it -- which

means I'm pretty happy, given that I have 60-80 AG-1B bulbs on hand).

 

Question is: will using a higher shutter speed (with this Alphax

press-type shutter) have the same effect I'm used to in terms of

reducing exposure, or do things get funky when I try to chop a chunk

out of the bulb's light curve?

 

For that matter, even if the shutter speed works just the way it

should, 1/200 will still only get me down to about six feet on ISO 400

with this lens (though I have a couple others I might use with this

flash that stop down to f/32 and will thus get down to eight feet or

so even at 1/50). Any good rules of thumb on using bounce or bare

bulb instead of direct "flat flash" in the bowl?

Shutter speed sould not effect exposure as much as changing the F-stop. I assume you are useing the M syc. and not X . I belive that not using the reflector will cut the light down 2 stops,if its a polished reflector. Shooting with a bare bulb give a nice even light through out a whole room.You might put a heat proof difuser over the flash reflector. I seem to remember seeing photos of guys using handkerchiefs over flashes.

Yep, I've used a paper napkin over a flash once, when I was too young to shave. Worked pretty well, as I recall. Bare bulb at two stops should be a good start. And I recall ceiling bounce requiring me to use the combined distance, flash to ceiling and ceiling to subject, then add a factor for the reflectivity of the ceiling (which was always something of a fudge, since you never really knew what it should be). Fortunately, this flash has a tilt feature, all the way to vertical if needed, and I have an off-camera bracket (the side mounted hot shoe on the Argoflex would pretty well nullify the tilt, otherwise).

 

Then one gets into the subject of trying to focus on that dim ground glass in a dim interior, but it looks like I'll have plenty of DOF...

Shutter speed has zero effect on flash exposure. You must either adjust the aperture or the power of the flash. The latter may be done by using a white hankerchief over the flash or bouncing the flash off a white wall (also gives better modelling). You could also use a neutral density filter or use a slower film speed.

Interestingly, I also discovered today (in the process of replacing the dead capacitor) that this flash can swivel *past* vertical, to face almost directly backward. What do you suppose the exposure factor is for that flash position? ;)

Shutter speed does have a effect on exposure with flashbulbs, not with electronic flash. Flashbubs came in several burn speeds.Most cameras were made to shoot at 30th and 60th of a second. If your shutter fires too fast you will get less exposure as you will be cutting off part of the burn cycle.Fashbulbs boxes list different guide numbers for different shutter speeds. As to your question about bouncing the light behind you ,its the same as off the ceiling. You measure the distance from the flash to the surface you are bouncing off of, and then add the distance from the bounce to the subject. If you are bouncing off a white wall this number will be a higher F-stop than off a dark wall.

Michael, I'm with you. I remember the bad old days too. Or perhaps we've both read the same books.

 

Donald, I'm feeling a little too lazy to go upstairs, hunt for a copy, and verify that the directions you need are in the Kodak Master Photoguide, but they should be. Get a copy, the older the better.

 

Cheers,

 

Dan

I think a saw a copy of that book at the local photo supply store (there's a joke -- they're changing to digital as fast as they can, hoping one-time sales of cameras and the little film processing they do will offset the losses they've taken when all the local studios stopped bringing in dozens of rolls of film per day). I'll have to check how old it is.

 

Meantime, bounce is probably the way to go -- it provides a more normal looking light anyway, both softer (due to the larger reflection spot) and less flat (because not direct from the camera). Bare bulb is a good second option...

 

Cutting off part of the burn cycle is exactly what I had in mind with my original question, thinking I could shorten my minimum distance by shooting at 1/200 instead of 1/50. Unfortunately, the AG-1B box I have in front of me gives GN only for 2" polished (mine is a 4" textured, probably similar) and for "up to 1/30" or "1/60" and the exposure calculator wheel on the flash says for "1/60 or slower".

 

I shot a couple samples at 1/200, I'll have to see what they look like when I get that roll developed. Meantime, bounce is the way, I think, with bare bulb as a good backup.

 

And now I'm wondering how slow my film would have to be to need a P25 -- the exposure calculator on the flash shows #5, but not P25; looks like #5 has GN close to 500 with ISO 400. Let's see, every two stops reduced GN by 2x, so to get GN of, say, 64, I'd need ISO 6. Maybe I can load my camera with a roll of enlarging paper and use the flash at f/11.

 

Sure do wish I could buy a hot shoe adapter like the one I have (hot shoe to PC), only with a 20 millisecond delay built in, so I could use it to connect my strobe. Much, much cheaper to operate, and I can just set f/8 and let the flash handle the exposure. Of course, I can't bounce that one without adding some hardware...

Can you put a neutral density filter on the lens? That should do it to reduce the light from your bulbs.

 

Bill

You'll find a guide number chart for various bulbs here: http://www.flashbulbs.com/

flash_info.htm .1/200 should get you down to about 7 feet.

Bill, if I had a neutral, it would solve this problem, but I don't own one, much less one that will fit the Argoflex.

 

Thanks, Brandon, I knew about that chart, but hadn't recalled it having GN for faster shutters. That's exactly what I was after -- 1/200 works pretty much as I expected, gating 5 ms of the early part of the bulb's peak output (there's a 10 or 15 ms delay in the M synch to allow the bulb to ignite and put the peak output inside the shutter's open time). That at least lets me get down to 7-8 feet (I had calculated as 6 based on the flash's calculator and the assumption that 1/200 would have half the guide number of 1/50 -- probably not a significant difference). I also see guide numbers for X synch at speeds below 1/30, which is handy (though mostly, for X, I'll just use my little automatic xenon flash).

 

Ah, a quick Google prompted by something at the flashbulbs.com reference answered a question -- the "Class M" and "Class MF" on some of the bulbs. Apparently Class M ("Magnesium", the majority of non-FP types) are bulbs with 18-20 ms time to half peak output, while Class MF ("Magnesium, fast-peak", I'm guessing) have only about 10 ms until half peak. That means the MF bulbs (which include M2 and AG-1, probably AG-3 as well) give full output at 1/100 in a shutter that uses the shorter delay (which, AFAIK, includes only one model of Graphex, though any M synch leaf shutter could be converted, just as they can be converted to X synch), but also allows them to sync on X at up to 1/30, even with a 35 mm focal plane shutter.

 

Cool stuff! Imagine where flashbulbs would be today if they hadn't been killed, almost overnight (so rapidly as to leave a multi-decade stock of them in warehouses!) by consumer priced xenon flashes. Low-output bulbs suitable for high speed films, fast-burn bulbs that will stop action -- the possibilities are endless, and they'd still be rather cheap if they were being made in the quantities they were in 1970...<div></div>

I don't have specific tables but as I remember foil filled flash bulbs were very slow burn for focal plane shutters like Speed Graphics, wire filled (look like steel wool) were faster burn and gas filled bulbs were the fastest burn. So bulb type would determine the fastest shutter speed you could use (as well as the delay time).

Charles, that's mostly correct. All flashbulbs are filled with oxygen under pressure, in order for the magnesium (or aluminum, zirconium or hafnium, depending on the bulb type and manufacturer) to combust. None use gaseous fuel that I've ever heard of -- there isn't a gas that will let you pack enough in the bulb to get good light output and that burns brightly enough to be suitable.

 

You're 100% correct, however, in the foil filled type being long burn, primarily for FP use (there are even larger foil-filled types with a burn time of close to a second, and immense light output -- they're mainly used for large cavern photography, big-hall banquet shots and the like; a single one equals dozens of professional strobes); these long burn bulbs have also been used to allow multiple photographers to share a flash -- they stay bright long enough for a human's reaction time to trip a shutter after the bulb ignites and still catch full output (though flash sharing was much more commonly done with open flash technique). All smaller bulbs are filled with wire/wool, but I expect the main difference between the MF fast ignition type and the M standard burn is the ignition filament -- a smaller, higher temperature filament that will ignite more quickly (possibly coupled with the high current deliver of BC type flashguns) helps the MF bulbs come up to peak 25% faster than the M type.

There where also some bulbs (type SM or SF I believe)made with a very fast burn time

that IIRC would get up to full light output and then extinguish in about 1/100, what

made them special, is that they where filled with a light emitting gas that would be

ignited by a strand of magnesium, other than that there was nothing in them but gas

(I don't have any idea what gas that might be.) They where mainly for box an other

simple camera's, because of there short burn they could stop action reasonably well.

However they could be used with any shutter with an F sync. They where about the

size of a Press 5 bayonet bulb, but had IIRC considerately less light output.

Donald,<br><br>Hi. I had seen your post wishing there was a delay adapter to allow use of electronic flash in M sync shutters. There are several designs, here's one I found while surfing awhile back:<br><br><a href="http://www.rmm3d.com/3d.encyclopedia/repairs/flash.delay/flash.delay.html">Click here for flash delayer link</a><br><br>I hope this link works. Maybe you can whip up something similar for your Argoflex? I have a little box which I found for peanuts on that great auction site which supposedly fits atop flashcube (not Magicube) cameras and is secured with a little springy fabric strap. It provides a PC outlet (not hot shoe, alas) for using electronic flash on flashcube burners.<br><br>And yes, flashbulbs are neat! I love the look on people's faces when I pull out a huge flash reflector for, say, my Kodak Tourist...<br><br>--Micah in NC