larry@kitty.UUCP (Larry Lippman) (01/16/89)
In article <4622@sfsup.UUCP>, dcm@sfsup.UUCP (David C. Miller, consultant) writes: > In article <13355@cup.portal.com> mmm@cup.portal.com (Mark Robert Thorson) writes: > > > >At the risk of enormous flames, both here and hereafter, the fine wire inside > >a flashbulb is magnesium wire. > > If I remember correctly, the wire is simply aluminum and the bulb is > filled with pure oxygen. That way if the bulb is broken (either by > accident or intent) it is rendered harmless. All of this recent speculation about the composition of flashbulbs is interesting, but it is incorrect. The most common filament wire used in current flashbulb production is an alloy of tungesten and rhenium. Pure tungsten has been used in the past. Aluminum or magnesium wire would never be suitable for a filament; such wire is too soft or brittle for use as a filament, in addition to having too high a resistsnce for a 3 volt firing circuit. The filament is coated with a small amount of "primer" material, generally a perchlorate mixture. The combustible "filler" material inside a flashbulb is generally finely-shredded zirconium. Magnesium and aluminum have been used in past years for the filler material, but they do not possess the spectral power distribution that is today ideal for color photography. During manufacture, a flashbulb is evacuated and heated to drive out moisture (which is the #1 killer for flashbulb failure). The bulb is then filled with pure oxygen under pressure - typically around 100 psi. The bulb is then coated with a protective lacquer to entrain any glass should the envelope burst. This lacquer is also used for color correction purposes, which is why it is blue in color. Following lacquer coating, the bulb is then coated with an anti-static material (yes, flashbulbs can be discharged by static electricity, and in early years people were injured when a flasbulb would fire after just being touched). When current is passed through a flashbulb, the filament heats and ignites the primer. Particles of the primer rapidly propagate through the flasbulb, igniting the zirconium filler material, which then combusts rapidly in the atmosphere of pure oxygen. Those of you with photographic expiernce probably know that a flashbulb (like an AG1) typically reaches peak illumination in about 15 milliseconds, with the effective photographic illumination being extinguished after an additional 25 or so milliseconds having elapsed. In case you are wondering, the Magicube flash lamp used in the Instamatic X cameras are fired _mechanically_ by means of a torsion spring which causes a striker arm to hit a percussion primer. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {att|hplabs|mtune|utzoo|uunet}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"
rjschw@hubcap.UUCP (Robert Schwartz) (01/16/89)
From article <2929@kitty.UUCP>, by larry@kitty.UUCP (Larry Lippman): > > In case you are wondering, the Magicube flash lamp used in the > Instamatic X cameras are fired _mechanically_ by means of a torsion spring > which causes a striker arm to hit a percussion primer. > Which of course makes it possible (although rare) for the cube to fire if it is dropped. That causes quite a reaction from the dropper and a bit of surprise to the people around. Of course, this generally will leave you with one less flash than pictures remaining on your roll. :-) -- Robert Schwartz UUCP: ...gatech!hubcap!rjschw Clemson University Internet: rjschw@hubcap.clemson.edu "The most valuable quotation will be the one for which you cannot determine the source." -- Who said that?
brian@sequent.UUCP (Brian Godfrey) (01/17/89)
I just read about an unusual "flashbulb" in the November National Geographic Magazine. Some explorers wanted to photograph a shipwreck at a depth of 800+ feet. They filled two glass fishing floats with 24 flash bulbs each and a remote triggering device. Then they suspended the floats out of view of the camera and fired. The picture was very well exposed, but was an eerie blue color. I think one of them failed to fire. I just wonder how they got 24 flash bulbs and a remote into a glass float in the first place. -- --Brian M. Godfrey Sequent Computer Systems Inc. !tektronix!sequent!brian
pfales@ttrde.UUCP (Peter Fales) (01/17/89)
In article <4104@hubcap.UUCP>, rjschw@hubcap.UUCP (Robert Schwartz) writes: > Which of course makes it possible (although rare) for the cube > to fire if it is dropped. That causes quite a reaction from the dropper > and a bit of surprise to the people around. Of course, this generally > will leave you with one less flash than pictures remaining on your roll. In my wilder and crazier days, we used to fashion darts out of straws and punch-cards and tape the bulb from a dis-assembled magicube to the end. When tossed against a hard surface they would go off almost every time. NOTE: For anyone attempting to duplicate this feat, it is dangerous (broken glass, etc.) Also note that these are the mechanically actuated "Magicubes" as opposed to the traditional electrical flashcubes. -- Peter Fales AT&T, Room 2F-217 200 Park Plaza UUCP: ...att!ttrde!pfales Naperville, IL 60566 Domain: pfales@ttrde.att.com work: (312) 416-5357
emartini%joey@Sun.COM (Ed Martini - Graphics Software) (01/17/89)
> 15 milliseconds, with the effective photographic illumination being > extinguished after an additional 25 or so milliseconds having elapsed. .015+.025 = 0.4 = 1/250 Much slower than most cameras are capable of? I thought flash sync was limited by the shutter action?? Ed???
emartini%joey@Sun.COM (Ed Martini - Graphics Software) (01/17/89)
In article <85595@sun.uucp>, emartini%joey@Sun.COM (Ed Martini - Graphics Software) writes: > > 15 milliseconds, with the effective photographic illumination being > > extinguished after an additional 25 or so milliseconds having elapsed. > > .015 + .025 = 0.04 = 1/25 > > Much slower than most cameras are capable of? > I thought flash sync was limited by the shutter action?? > > Ed??? oops, this is what I really meant.
awpaeth@watcgl.waterloo.edu (Alan Wm Paeth) (01/18/89)
In article <9776@sequent.UUCP> brian@crg1.UUCP (Brian Godfrey) writes: > > I just read about an unusual "flashbulb" in the November National >Geographic Magazine. Some explorers wanted to photograph a shipwreck at >a depth of 800+ feet. They filled two glass fishing floats with 24 flash >bulbs each and a remote triggering device. Then they suspended the floats... I had a chance to consult for the NGS in 1980 and spent not a small amount of time looking over their color and b/w darkroom facilities, with a lot of time spent talking with staff photographers (because the contract involved electronic color printing but also because the facilities and photographic staff were tremendous to visit). Their need for high illumination levels at very great depths led them to designs using spherical glass ampules filled with plastic explosives -- given the pressures involved (say, 10,000psi) they reasoned that most of the useful output would be in the form of light. They were essentially giant flashbulbs! An article on undersea phototography a year or so back led me to believe they'ed given up on the idea. Maybe no assistants could be found to hold the remotes :-). /Alan Paeth Computer Graphics Laboratory University of Waterloo BTW - Brian's interesting description of multiple flash tubes per enclosure reminded me to ask the net: is anyone else asking local photofinishers to save the discardable "Fuji Quick-step" flashes? Good either for a fully functional 1.5v flash circuit with tube and ready light, or for one rather large electrolytic + misc. if salvaged for parts.
brian@sequent.UUCP (Brian Godfrey) (01/18/89)
>> .015 + .025 = 0.04 = 1/25 >> Much slower than most cameras are capable of? >> I thought flash sync was limited by the shutter action?? To sync to a flash you must make sure the shutter is all the way open before the flash fires (begins emitting light.) To get reproducible exposures you must ensure that the flash is finished firing before the shutter closes. (Actually the filaments in flash bulbs glow for a while, but that doesn't count.) There are three basic syncing problems: electronic flash, bulbs & leaf shutters, and bulbs & focal plane shutters. Electronic flash is extremely fast, ranging generally from 1/5000 to 1/25000. With electronic flash you have to make sure and wait until the shutter is all the way open before triggering the flash. This takes from 1/250 sec on some cameras to 1/60 sec on others. The actual exposure happens very quickly. Then the shutter closes at its leisurely pace. With flash bulbs (the above equation is for flash bulbs) and leaf shutters you have to trigger the flash, then wait for a bit while its filament is heating up before tripping the shutter, the object being to have the shutter fully open at the same time as the light arrives from the bulb. In the above case, the bulb will be emitting light for 1/25 of a second. If you wanted truly accurate and reproducible exposures you would have to use 1/25 sec shutter speed. Actually, I think you can cut off some of the rise and fall time without affecting the exposure appreciably. Focal plane shutters and flash bulbs have a little bit different timing. Leaf shutters open very quickly, so you triggered the flash then waited for most of the 15 milliseconds before opening the shutter. Focal plane shutters open very slowly. If your sync speed on a focal plane camera is 1/60 sec, then that is how long it takes for the shutter to open. 1/60 sec is about 16 ms which is very close to the 15 ms it takes for the flash to warm up. In this case your camera will have to trip the shutter and trigger the flash at the same time in order for the light to begin striking the film at the same time as the shutter is fully open. But at 1/60 sec (16 ms) you will be closing the shutter long before the bulb has fully discharged (40 ms). Your sync speed for this bulb would still be 1/25 sec on a camera with a focal plane shutter, though you would probably have no problem with 1/30 sec which is more common on focal plane shutters. With different bulbs you will probably have different sync speeds. Cameras and shutters before electronic flash probably didn't have to worry about these different syncing schemes (although they may have had flash powder to worry about.) Modern cameras probably don't have provision to sync to bulbs. Cameras in the transition period (1950s to 1980s) did make provision for both schemes while applied to them. My old OM-1 (1975) has a switch for "FP" or "X". "FP" is for bulbs (stands for Flash Powder??) and "X" is for electronic flash. My old Linhoff (I think it is 1950s vintage) has settings on the shutter for "M" and "X" sync. "M" is also for bulbs, though I have no idea what it means. Maybe a loremaster knows the meanings of the abbreviations. I have never looked to see if there is a special setting on my OM-4 for bulbs. I vaguely remember reading some- thing about it in the manual, but it may have just said to use an extremely slow shutter speed to give the bulb time to warm up while the shutter is open. Hope this was helpful. -- --Brian M. Godfrey Sequent Computer Systems Inc. !tektronix!sequent!brian
beyer@houxs.ATT.COM (J.BEYER) (01/18/89)
In article <85595@sun.uucp>, emartini%joey@Sun.COM (Ed Martini - Graphics Software) writes: > > 15 milliseconds, with the effective photographic illumination being > > extinguished after an additional 25 or so milliseconds having elapsed. > > .015+.025 = 0.4 = 1/250 > > Much slower than most cameras are capable of? > I thought flash sync was limited by the shutter action?? For those cameras equipped with M flash contacts, there is a delay that I believe is around 17 milliseconds between when the contacts close and the shutter opens. At least, that delay for most flash bulbs. For focal plain shutters, there is an FP type flashbulb (or there was, I don't know if you can get them any more) that started burning before the shutter curtain started to move, and burned at a 'constant' rate until the shutter closed again. I find it hard to believe that they were constant enough (I never used any), but maybe they were. On most 35mm SLR cameras a focal plane shutter is used. Only an X (instantaneous) contact is provided on many of these. Even my new Copal #1 shutters have only X contacts. My old one can selece X or M. OK with me because I do not use flash bulbs. For these, only very long exposures can be used with flash bulbs because you want the entire shutter to be open for the entire useful burn time of the bulb. -- Jean-David Beyer A.T.&T., Holmdel, New Jersey, 07733 houxs!beyer
donl@glass.SGI.COM (donl mathis) (01/19/89)
In article <9844@sequent.UUCP>, brian@sequent.UUCP (Brian Godfrey) writes: > >> .015 + .025 = 0.04 = 1/25 > >> Much slower than most cameras are capable of? > >> I thought flash sync was limited by the shutter action?? > > To sync to a flash you must make sure the shutter is all the way open > before the flash fires (begins emitting light.) To get reproducible > .. > Electronic flash is extremely fast, ranging generally from 1/5000 to > 1/25000. With electronic flash you have to make sure and wait until the Many electronic flashes fire much slower, often less than a 1/1000, particularly larger studio flashes. On-camera flashes shut down much faster when less light is required. > Leaf shutters open very quickly, so you triggered the flash then waited > for most of the 15 milliseconds before opening the shutter. Focal plane It's my understanding that leaf shutters trigger the flash when they are fully open, at least on X-sync (which is the only option on my Copal shutters, and on my dad's Seiko shutters). The time spent opening and closing is therefore irrelevent, as far as the flash is concerned. -- - donl mathis at Silicon Graphics Computer Systems, Mountain View, CA {sun,pyramid,adobe,decwrl,ucbvax,allegra}!sgi!donl donl@sgi.com
larry@kitty.UUCP (Larry Lippman) (01/19/89)
In article <85625@sun.uucp>, emartini%joey@Sun.COM (Ed Martini - Graphics Software) writes: > > > 15 milliseconds, with the effective photographic illumination being > > > extinguished after an additional 25 or so milliseconds having elapsed. > > > > .015 + .025 = 0.04 = 1/25 > > > > Much slower than most cameras are capable of? > > I thought flash sync was limited by the shutter action?? I am looking at a book which has light output curves of various flashbulbs. There seems to be three timing parameters: (1) half-peak time; (2) peak time; and (3) effective duration. Looking at the curve for an AG1B, there is essentially zero light output for the first 5 milliseconds. The half-peak time (i.e., elapsed time from firing) is around 8 milliseconds where light output reaches about 225,000 lumens. The peak time (i.e., elapsed from firing) is around 14 milliseconds, where light output reaches about 450,000 lumens. The effective duration time is around 20 milliseconds (i.e., from beginning half-peak time to ending half-peak time). So far, we have elapsed about 28 milliseconds. At 40 milliseconds total elapsed time, there is still around 50,000 lumens of light - no where near peak, but not insignificant either. Total light extinction occurs at an elapsed time of around 46 milliseconds. With X-synchronization there is virtually no shutter delay, and the spec says the shutter must be at least 80% open 1 millisecond after firing. With M-synchronization there is a shutter delay, and the spec says that the shutter must be fully open by 15 +/- 2 milliseconds. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {att|hplabs|mtune|utzoo|uunet}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"
dr@skivs.UUCP (David Robins) (01/20/89)
In article <9844@sequent.UUCP> brian@crg1.UUCP (Brian Godfrey) writes: > > To sync to a flash you must make sure the shutter is all the way open >before the flash fires (begins emitting light.) To get reproducible >exposures you must ensure that the flash is finished firing before the >shutter closes. (Actually the filaments in flash bulbs glow for a while, >but that doesn't count.) > ... >a switch for "FP" or "X". "FP" is for bulbs (stands for Flash Powder??) >and "X" is for electronic flash. My old Linhoff (I think it is 1950s >vintage) has settings on the shutter for "M" and "X" sync. "M" is also >for bulbs, though I have no idea what it means. Maybe a loremaster knows Actually, I recall that "FP" stood for focal plane type bulbs. M synch was for standard flashbulbs. I don't recall the exact heat-up times, but they were somewhat different for FP & M lamps, so the flash contact lead times were different. Type M lamps had a strong peak in the output. FP lamps had more of a plateau. The reason was the M lamps were for leaf shutter cameras, where the shutter is fully open during the exposure, except for the rapid lead open/close period. Thus, a peak would not cause exposure non-uniformity across the film. Focal plane shutters, when in speeds higher than the X-synch speed where it is fully open, are actually a slit moving across the film at a steady speed. The exposure for these higher speeds is varied by changing the width of the slit. This is whey, if you use a strobe flash at a speed higher than the X-synch speed, it cuts of part of the picture where the slit has not uncovered the film. For focal plane shutters to get uniform flash exposures with higher speeds, with the moving slit, the plateau light output of FP lamps is needed. The plateau must be longer than the focal plane travel time. You don't have to have the shutter stay open until the lamp goes out to get reproducible results. As long as the illumination is stable from lamp to lamp, you can use any shutter speed. As an example, my old leaf-shutter camera used M bulbs (the Honeywell capacitor flash took AG-1's, M-2's, and 25's.) The most exposure happens of course if you use the whole illumination curve of the lamp, using shutter durations of ~ 1/30 sec. But you could use faster speeds, but you needed bigger f-stops to get the exposure, since you used only part of the light. The table on the back of the AG-1 and M-2 boxes had tables for shutter speed vs. f-stop. My Nikon F (circa 1968) has 4 flash synch settings - X, FP, green dot, and red dot. The X is strobe flash; no pre-opening lead time. FP was for FP lamps. The red and green dots were for M lamps, as I recall, and were different lead times for the synch closure. The instruction manual had a complex table of lamp type, shutter speed, and synch type. -- David Robins, M.D. (ophthalmologist / electronics engineer) The Smith-Kettlewell Institute of Visual Science, *** net: uunet!skivs!dr 2232 Webster St, San Francisco CA 94115 *** 415/561-1705 (voice) The opinions expressed herein do not reflect the opinion of the Institute!
consult@osiris.UUCP (Unix Consultation Mailbox ) (01/20/89)
In article <9844@sequent.UUCP> brian@crg1.UUCP (Brian Godfrey) writes: >Modern cameras probably don't have provision >to sync to bulbs. Cameras in the transition period (1950s to 1980s) did make >provision for both schemes while applied to them. My old OM-1 (1975) has >a switch for "FP" or "X". "FP" is for bulbs (stands for Flash Powder??) >and "X" is for electronic flash. My old Linhoff (I think it is 1950s >vintage) has settings on the shutter for "M" and "X" sync. "M" is also >for bulbs, though I have no idea what it means. And then there's the more common but no less mysterious "B" setting, which I've always heard "translated" as "bulb", which holds the shutter open as long as you hold the shutter release button. Is this intended for syncing to flash bulbs? (I always used it for exposures longer than the camera wanted to time itself, like those pictures of the full moon shot with long f >= 8 lenses for ~30 seconds with Tri-X that we then pushed to about 1600ASA...) Phil Kos
nusip@maccs.McMaster.CA (Mike Borza) (01/20/89)
In article <9844@sequent.UUCP> brian@crg1.UUCP (Brian Godfrey) writes: > There are three basic syncing problems: electronic flash, bulbs & leaf >shutters, and bulbs & focal plane shutters. > Electronic flash is extremely fast, ranging generally from 1/5000 to >1/25000. With electronic flash you have to make sure and wait until the >shutter is all the way open before triggering the flash. This takes from >1/250 sec on some cameras to 1/60 sec on others. The actual exposure >happens very quickly. Then the shutter closes at its leisurely pace. Pardon my ignorance, but... doesn't this mean that shutter speed is essentially irrelevant for a flash picture taken using an electronic flash? If so, how does one control the exposure? (sci.photography what?) mike borza <nusip@maccs.uucp>
davef@brspyr1.BRS.Com (Dave Fiske) (01/20/89)
In article <4104@hubcap.UUCP>, rjschw@hubcap.UUCP (Robert Schwartz) writes: > From article <2929@kitty.UUCP>, by larry@kitty.UUCP (Larry Lippman): > > In case you are wondering, the Magicube flash lamp used in the > > Instamatic X cameras are fired _mechanically_ by means of a torsion spring > > which causes a striker arm to hit a percussion primer. > Which of course makes it possible (although rare) for the cube > to fire if it is dropped. That causes quite a reaction from the dropper > and a bit of surprise to the people around. Of course, this generally Or, just use a small screwdriver to trip the little lever--making sure your hand is not touching the side which will fire. Someone in my family once bought some Magic cubes instead of regular flashcubes, and rather than see them go to waste, I played around with them. It does startle people, since they don't see any camera. They don't understand where the sudden lightning flash came from. -- "FLYING ELEPHANTS DROP COW Dave Fiske (davef@brspyr1.BRS.COM) PIES ON HORRIFIED CROWD!" Home: David_A_Fiske@cup.portal.com Headline from Weekly World News CIS: 75415,163 GEnie: davef
brian@sequent.UUCP (Brian Godfrey) (01/20/89)
>> Leaf shutters open very quickly, so you triggered the flash then waited >> for most of the 15 milliseconds before opening the shutter. Focal plane > >It's my understanding that leaf shutters trigger the flash when they >are fully open, at least on X-sync (which is the only option on my Copal >shutters, and on my dad's Seiko shutters). The time spent opening and closing >is therefore irrelevent, as far as the flash is concerned. I mentioned this, but it was probably lost in all verbage. :-) X-sync does trigger the flash when the shutter is fully open. But the paragraph above is in relation to bulbs. You would not have flash sync all the way up to 1/500 sec if the flash was triggered when the shutter was fully open. My Compur shutters are pretty old and still have "M" and "X" sync. "M" is for bulbs, "X" is for electronic flash. The timing is different. -- --Brian M. Godfrey Sequent Computer Systems Inc. !tektronix!sequent!brian
beyer@houxs.ATT.COM (J.BEYER) (01/20/89)
In article <2818@osiris.UUCP>, consult@osiris.UUCP (Unix Consultation Mailbox ) writes: > In article <9844@sequent.UUCP> brian@crg1.UUCP (Brian Godfrey) writes: > >Modern cameras probably don't have provision > >to sync to bulbs. Cameras in the transition period (1950s to 1980s) did make > >provision for both schemes while applied to them. My old OM-1 (1975) has > >a switch for "FP" or "X". "FP" is for bulbs (stands for Flash Powder??) > >and "X" is for electronic flash. My old Linhoff (I think it is 1950s > >vintage) has settings on the shutter for "M" and "X" sync. "M" is also > >for bulbs, though I have no idea what it means. > FP stands for bulbs designed for focal plane shutters. They have a long burn time, at least as long as the shutter curtain travel time. M was for medium delay bulbs. There were also short and long delay bulbs, but I do not remember (from my reading, I never used any flash bulbs except some #25B's with a Brownie Hawkeye) their codes. > And then there's the more common but no less mysterious "B" setting, > which I've always heard "translated" as "bulb", which holds the shutter > open as long as you hold the shutter release button. Is this intended > for syncing to flash bulbs? (I always used it for exposures longer than > B does stand for BULB, but it refers to the squeeze bulb at the end of a long rubber (in those days, mine is plastic tubing) that can be used for remote control of a shutter. The shutter stayed open for as long as the bulb was squeezed so you could adjust exposure time without going to the camera. In the old days, film was slow enough that this made sense. In fact some manufacturers had "controlled" leaks so that you could make a fixed time exposure by seeting the leak rate. I bet the reliability was not very good. On my shutters there is both B and T positions. On B, the shutter remains open for as long as I hold the bulb. On T, the shutter opens on the first squeeze and closes on the second. On some old German shutters, T is called Z (I believe Zeit is German for Time, but I only took one year of it 30 years ago.) > Phil Kos -- Jean-David Beyer A.T.&T., Holmdel, New Jersey, 07733 houxs!beyer
jad@dayton.UUCP (John A. Deters) (01/20/89)
In article <2818@osiris.UUCP> consult@osiris.UUCP (Unix Consultation Mailbox (Phil)) writes: > >And then there's the more common but no less mysterious "B" setting, >which I've always heard "translated" as "bulb", which holds the shutter >open as long as you hold the shutter release button. Is this intended >for syncing to flash bulbs? (I always used it for exposures longer than >the camera wanted to time itself, like those pictures of the full moon >shot with long f >= 8 lenses for ~30 seconds with Tri-X that we then >pushed to about 1600ASA...) > >Phil Kos The B does stand for Bulb, but not 'flashbulb'. The bulb they are talking about comes from the old cameras that were triggered by a pneumatic squeeze bulb. There was a piston that screwed into the trigger assembly, an air hose, and a squeeze bulb on the end of the hose with a hole in it. The photographer would cover the hole with his thumb, squeeze the bulb for as long as he wanted to expose the picture, then release his thumb to close the shutter. -john
brian@sequent.UUCP (Brian Godfrey) (01/21/89)
>And then there's the more common but no less mysterious "B" setting, >which I've always heard "translated" as "bulb", which holds the shutter >open as long as you hold the shutter release button. Is this intended >for syncing to flash bulbs? (I always used it for exposures longer than No, the "B" setting is on the shutter speed dial and is translated just as you did - "bulb". It comes from the old kind of shutter releases which were made of a tube and an air bulb which, when squeezed, released the shutter. Most people use cable releases, now, but you can still get the bulb releases. In a way, "B" can be used as yet another sync method. You can open the shutter on the "B" setting and lock it open, then go around and flash a strobe where you want light to appear. (This must, obviously, be done in the dark or the film will quickly overexpose.) -- --Brian M. Godfrey Sequent Computer Systems Inc. !tektronix!sequent!brian
hofbauer@csri.toronto.edu (John Hofbauer) (01/21/89)
>Pardon my ignorance, but... doesn't this mean that shutter speed is >essentially irrelevant for a flash picture taken using an electronic >flash? If so, how does one control the exposure? > Yup. Exposure is controlled by the aperture selected. It's the old inverse square law in action.
ark@alice.UUCP (Andrew Koenig) (01/21/89)
In article <1818@maccs.McMaster.CA>, nusip@maccs.McMaster.CA (Mike Borza) writes: > Pardon my ignorance, but... doesn't this mean that shutter speed is > essentially irrelevant for a flash picture taken using an electronic > flash? If so, how does one control the exposure? Correct -- shutter speed is irrelevant for pictures taken with electronic flash. You can vary three things to control exposure: aperture, distance from flash to subject, and flash intensity. Some flash units do not allow the intensity to be varied. Others have sensors that measure the amount of light reflected from the subject and adjust the intensity appropriately. -- --Andrew Koenig ark@europa.att.com
chip@vaxwaller.UUCP (Chip Kozy) (01/21/89)
In article <25113@sgi.SGI.COM>, donl@glass.SGI.COM (donl mathis) writes:
.
. It's my understanding that leaf shutters trigger the flash when they
. are fully open, at least on X-sync (which is the only option on my Copal
. shutters, and on my dad's Seiko shutters). The time spent opening and closing
. is therefore irrelevent, as far as the flash is concerned.
That's the story I get, too. With the flash held off until the
shutter is completely open shutter speed itself becomes irrelevant to a
greater degree. That's why my Mamiyas will sync at any speed up to 1/500th
sec...the max the lenses will do. (BTW they also have another setting for
flashbulbs, but, since it's after coffee break, I'll have to look at it
again before I can remember what it's called.)
Sto lat;
Chip
,,
*** SOLIDARNOSC ***
"Take only pictures, leave only footprints." J. Muir
--
Chip Kozy (415) 939-2400 @ Varian 2700 Mitchell Dr. Walnut Creek, Cal. 94598
...!pacbell!varian!vaxwaller!chipgbell@pnet12.cts.com (Greg Bell) (01/22/89)
Can we PLEASE get all NON electronics related conversation OFF THIS
NEWSGROUP???????????? This is VERY inconsiderate.
Greg Bell_________________________________________________________
Hardware hacker |
Electronics hobbyist | UUCP: uunet!serene!pnet12!gbell
EE major at UC San Diego |sukenick@ccnysci.UUCP (SYG) (01/23/89)
>> Pardon my ignorance, but... doesn't this mean that shutter speed is >> essentially irrelevant for a flash picture taken using an electronic >> flash? If so, how does one control the exposure? >Correct -- shutter speed is irrelevant for pictures taken >with electronic flash. True, for purposes of exposure (unless your shutter speed is faster than 1/10,000 :-) ), but the shutter curtain has to be wide open when the flash goes off. For faster speeds, the curtain will be a slit moving across the negative and you will get a perfectly exposed column or row of the scene. Usually, the curtain will be wide open at speeds equal or slower than 1/60 or 1/125, depending on the camera. The fastest speed usable with a flash is usually the flash position on the shutter speed dial; although you can use a slower speed. You can see the effect if you're willing to waste a frame; just turn to 1/1000 take a pic with a flash. Never mind if you have leaf shutters as on many 120 film cameras : you can use any shutter speed since there is no shutter curtain.
brian@sequent.UUCP (Brian Godfrey) (01/23/89)
>Pardon my ignorance, but... doesn't this mean that shutter speed is >essentially irrelevant for a flash picture taken using an electronic >flash? If so, how does one control the exposure? Shutter speed is relevent to the extent that the shutter must be all the way open before the flash is triggered. (The question was in respect to electronic flash, contrary to the subject line, above.) You can control the exposure with the aperture setting. Some flash units allow you to control the flash power. You can change the distance the light from the flash has to travel (inverse square law). Autoflash and TTL autoflash control exposure by limiting flash duration. -- --Brian M. Godfrey Sequent Computer Systems Inc. !tektronix!sequent!brian
brian@sequent.UUCP (Brian Godfrey) (01/23/89)
>FP stands for bulbs designed for focal plane shutters. They have a long >burn time, at least as long as the shutter curtain travel time. Yeah, by the strangest coincidence Shutterbug has an article on flash bulbs this month and I just read the same thing. >M was for medium delay bulbs. There were also short and long delay bulbs, >but I do not remember (from my reading, I never used any flash bulbs >except some #25B's with a Brownie Hawkeye) their codes. According to the article there were "SM" bulbs with 1/200 flash durations. They didn't give durations for other types. There are probably lots of old photography books running around with that kind of info if anyone wanted to know it. By the way, they mentioned a guy who takes large (12X20 inch negatives) group portraits. He uses flash bulbs because he gets more light for the dollar. Equivalent electronic flash would cost him $70,000 in equipment, result in massive tangles of cabling, would weigh half a ton, and would consume 15,000 watts of electricity. His flash equipment cost him $500, weighs 200 lbs, and uses trivial amount of electricity. -- --Brian M. Godfrey Sequent Computer Systems Inc. !tektronix!sequent!brian
beyer@houxs.ATT.COM (J.BEYER) (01/23/89)
In article <1818@maccs.McMaster.CA>, nusip@maccs.McMaster.CA (Mike Borza) writes: > In article <9844@sequent.UUCP> brian@crg1.UUCP (Brian Godfrey) writes: > > Electronic flash is extremely fast, ranging generally from 1/5000 to > >1/25000. With electronic flash you have to make sure and wait until the > >shutter is all the way open before triggering the flash. This takes from > >1/250 sec on some cameras to 1/60 sec on others. The actual exposure > >happens very quickly. Then the shutter closes at its leisurely pace. > My electronic flash units last 1/300 second at maximum power. > Pardon my ignorance, but... doesn't this mean that shutter speed is > essentially irrelevant for a flash picture taken using an electronic > flash? If so, how does one control the exposure? Shutter speed, in a dark room does not matter when taking electronic flash pictures. In a lighted room, or outdoors, if the shutter is open long enough, the available light will also participate in making the image, and many techniques may be used for special effects. In those cases where the electronic flash unit provides most of the light, the exposure is determined by the light output of the flash and the aperture of the lens. -- Jean-David Beyer A.T.&T., Holmdel, New Jersey, 07733 houxs!beyer
beyer@houxs.ATT.COM (J.BEYER) (01/24/89)
In article <10096@sequent.UUCP>, brian@sequent.UUCP (Brian Godfrey) writes: > By the way, they mentioned a guy who takes large (12X20 inch negatives) > group portraits. He uses flash bulbs because he gets more light for the > dollar. Equivalent electronic flash would cost him $70,000 in equipment, > result in massive tangles of cabling, would weigh half a ton, and would > consume 15,000 watts of electricity. His flash equipment cost him $500, > weighs 200 lbs, and uses trivial amount of electricity. While there is probably more light per dollar, per pound, and per cubic inch, in flashbulbs, provided that only one exposure is desired, I cannot believe it would require 15 kilowatts of electricity to run a lot of electronic flash units unless extremely fast recycling is desired. My White Lightning units, for example, draw at most 2 amperes from the AC line. This could be cut at least in half by removing the 100 watt modelling lamps. Rounding off the numbers, if each WL unit drew 100 watts, I could use 150 of the things to come up with 15KW. That would be a lot of light. You can always use more flashbulb power than what 150 WL units would provide, but for the second exposure, you must replace all the flashbulbs. Think of the poor guy that used to photograph entire 150 car railroad trains at night with flashbulbs. Bet you he only made one exposure per night. The really big studio flash units contain transformers that increase the weight, and many put out more than the 250 joules that the WL10000's do. But much of the increased power is so they recycle faster than the 3 seconds the WLs require, and to power the 600watt quartz-halogen modelling lamps. How many flashbulbs did whoever need to replace 15Kw of electronic flash? -- Jean-David Beyer A.T.&T., Holmdel, New Jersey, 07733 houxs!beyer
brian@sequent.UUCP (Brian Godfrey) (01/26/89)
>> By the way, they mentioned a guy who takes large (12X20 inch negatives) >> group portraits. He uses flash bulbs because he gets more light for the... Mr. Beyer is surprised at the power draw of equivalent electronic flash. Actually, the point in telling about this particular photographer was to point out how much more light you can get out of simple flash bulbs. He used 30 of the large bulbs (the kind with house-hold light socket bases.) I doubt if he used a motor drive in his 12X20 camera, so changing bulbs probably was not such a big deal. :-) >Think of the poor guy that used to photograph entire 150 car railroad trains >at night with flashbulbs. Bet you he only made one exposure per night. Actually they mentioned "him" as well. (Actually, there were a number of people who did that and train freaks still do. They like flash bulbs because you get more light per "pop" and so do not have to wait for so many recharges.) >How many flashbulbs did whoever need to replace 15Kw of electronic flash? 30. -- --Brian M. Godfrey Sequent Computer Systems Inc. !tektronix!sequent!brian