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Photo Forum / Digital Photography / DSLR Cameras / December 2005Is X-Sync speed a "big deal" anymore - now that we have High-speed synch on powerful flash units?
Hi all, I've been plowing through an online "book" on Canon EOS Flash Photography http://photonotes.org/articles/eos-flash/ (OK - it's really just a web page, but ran to 99 pages when I copied and pasted it into Word). In the past I've occasionally come up against the 20D's 1/250th X-Sync "limitation" - I knew that I could go faster if I used High Speed Sync, but for some reason I had it in my mind that High Speed Sync (or FP Mode) was vastly inferior, and was likely to get poorly metered results. How wrong can a mouse be? Having read through the article it appears that the only limitation is that it efectively reduces the output of the unit by around 1/3 - often a non-issue with big monsters like the 580EX (especially several of them). To "prove the point" I setup my 20D on manual and in a room with very subdued lighting I set it for 1/250 (and some at 1/500) - F2.8 - F5.6 - attached my remote transmitter, and let rip with a couple of 580EX's pointed at my victims. The result? EVERY one absolutely spot on - PERFECT exposure. The only limitation I hit was the 580EX not being able to cycle fast enough when I fired a burst of shots. With this in mind, it begs me to ask the question: "Is an X-Sync speed of "this" or "that" simply irrelivant in this day and age? Additionally, can anyone think of a reason why Canon couldn't even give us a custom function that says "Use FP Mode when >1/250 of a Sec"? Would be interested to hear peoples thoughts. > The only limitation I hit was the 580EX not being able to cycle fast enough > when I fired a burst of shots. > > With this in mind, it begs me to ask the question: "Is an X-Sync speed of > "this" or "that" simply irrelivant in this day and age? High-speed sync works differently from normal flash mode in that the flash actually becomes "slower" -- it fires multiple pulses instead of a single flash, and thus is not good for stopping motion -- the exposure time is actually controlled by the shutter speed, whereas the flash duration is much shorter in normal mode. Other disadvantages: the flash may use more battery power and recycle more slowly, and will give you less total exposure; you can't calculate flash exposure using flash power (guide number) and aperture any more; and it will only work with a dedicated electronic flash unit. Apart from that, there's no reason not to use it. As you discovered, it does work as advertised. It's just not a "real" flash sync mode.  SignatureJeremy | jeremy@exit109.com > High-speed sync works differently from normal flash mode in that the flash > actually becomes "slower" -- it fires multiple pulses instead of a single > flash, and thus is not good for stopping motion -- the exposure time is > actually controlled by the shutter speed, whereas the flash duration is > much shorter in normal mode. Then again, if you're shooting with a shutter speed of upwards of 1/250th, isn't that going to freeze most motion anyway? > Other disadvantages: the flash may use more battery power and recycle > more slowly, and will give you less total exposure; you can't calculate > flash exposure using flash power (guide number) and aperture any more; > and it will only work with a dedicated electronic flash unit. I've only ever tried it in Av and Tv and M modes, but left the camera to sort out the (foreground) exposure - so far it seems to be able to hit the nail on the head everytime. > Then again, if you're shooting with a shutter speed of upwards of 1/250th, > isn't that going to freeze most motion anyway? Not nearly as well as a flash that's at least an order of magnitude faster. > I've only ever tried it in Av and Tv and M modes, but left the camera to > sort out the (foreground) exposure - so far it seems to be able to hit the > nail on the head everytime. It should work fine, you just need to understand its limits. SignatureJeremy | jeremy@exit109.com >> High-speed sync works differently from normal flash mode in that the flash >> actually becomes "slower" -- it fires multiple pulses instead of a single >> flash, and thus is not good for stopping motion -- the exposure time is >> actually controlled by the shutter speed, whereas the flash duration is >> much shorter in normal mode. >Then again, if you're shooting with a shutter speed of upwards of 1/250th, >isn't that going to freeze most motion anyway? 1/320 is about 30x as long as the shortest normal sync flash possible, and will not stop a swung baseball bat, or the wing of a bird in motion (or even its head). In addition, the frame is exposed in vertical strips over a period slightly longer than the stated exposure time with high-speed (as is also true of ambient light exposures faster than the sync speed, as well). Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< C J Southern skrev: > Hi all, > [quoted text clipped - 6 lines] > for some reason I had it in my mind that High Speed Sync (or FP Mode) was > vastly inferior, and was likely to get poorly metered results. http://www.kenrockwell.com/tech/syncspeed.htm SignatureMed venlig hilsen, Ole Larsen. New Images And Design 2005-11-17 http://home.tiscali.dk/muggler > http://www.kenrockwell.com/tech/syncspeed.htm Interesting article, but from what I've read previously, his "limitations" don't appear to totally hold true in a Canon EOS Flash environment ... eg. "On every camera I own the FP mode reverts back to totally manual exposure calculation" - I guess he doesn't own a Canon 20D or above, because the metering works just fine in TV, AP, and M modes. "The flash always pops at full power on the flashes I've seen. Thus as above you lose battery life, have long recycle times, no high frame rates and all the other disadvantages above." - It probably does, but that doesn't mean it's on at full power for long - or any longer than it would have been at the X-Sync shutter speed. From what I've read it's pulsed at 50,000 times per second. "Since only a fraction of the light at any time is exposing the film or CCD you lose a lot of light, again getting you back to the problems of limited flash range" - Others have said "you lose about 1/3" (personally, I wouldn't know) - again, with multiple, powerful units like the 580EX I wondr how much of an issue this is? >"Since only a fraction of the light at any time is exposing the film or CCD >you lose a lot of light, again getting you back to the problems of limited >flash range" - Others have said "you lose about 1/3" (personally, I wouldn't >know) - again, with multiple, powerful units like the 580EX I wondr how much >of an issue this is? With the 20D and 550EX, normal-sync GN (at 105mm) is 55 (meters), and drops to 24.3 at 1/320. GN at 1/8000 is 4.9. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > Would be interested to hear peoples thoughts. I found this article: http://www.photozone.de/3Technology/flashtec5.htm B. > I found this article: http://www.photozone.de/3Technology/flashtec5.htm Thanks for that - it helped to plug up a few of the gaps in my FP knowledge. > Hi all, > [quoted text clipped - 35 lines] > > Would be interested to hear peoples thoughts. The relevance come in when you are working in the studio with strobes, and a faster shutter speed would allow you to lessen your depth of field. SignatureSkip Middleton http://www.shadowcatcherimagery.com > The relevance come in when you are working in the studio with strobes, and > a faster shutter speed would allow you to lessen your depth of field. I take it that this is because studio strobes put out a pre-set amount of light, whereas in an E-TTL (2) system the camera can just shut off the light source when it's had enough light? >> The relevance come in when you are working in the studio with strobes, >> and a faster shutter speed would allow you to lessen your depth of field. > > I take it that this is because studio strobes put out a pre-set amount of > light, whereas in an E-TTL (2) system the camera can just shut off the > light source when it's had enough light? Not necessarily preset, but limited. Some sets of strobes, like my cheap ones, have only a couple of stops of latitude in their settings others have considerably more, but a max synch speed of 1/250, or in my 5Ds case, 1/200, can lead you to shooting at f8 more than one would like. SignatureSkip Middleton http://www.shadowcatcherimagery.com > Not necessarily preset, but limited. Some sets of strobes, like my cheap > ones, have only a couple of stops of latitude in their settings others > have considerably more, but a max synch speed of 1/250, or in my 5Ds case, > 1/200, can lead you to shooting at f8 more than one would like. So in that situation you can't shoot at, say F4 @ 1/125 because it won't freeze any motion, and you can't shoot at F4 @ 1/200 because the strobes don't have enough grunt (or if they do they wash out skin tones etc)? >> Not necessarily preset, but limited. Some sets of strobes, like my cheap >> ones, have only a couple of stops of latitude in their settings others [quoted text clipped - 4 lines] > freeze any motion, and you can't shoot at F4 @ 1/200 because the strobes > don't have enough grunt (or if they do they wash out skin tones etc)? Something like that. Full power on my strobes results in a meter reading of f16 and 1/250. So, two stops either gets me f11 and 1/125, f8 and 1/250 or f22 and 1/60th. A shutter of 1/500 would get me to f5.6, large enough to get the backdrop nice and soft... SignatureSkip Middleton http://www.shadowcatcherimagery.com >>> Not necessarily preset, but limited. Some sets of strobes, like my >>> cheap ones, have only a couple of stops of latitude in their settings [quoted text clipped - 10 lines] > 1/250 or f22 and 1/60th. A shutter of 1/500 would get me to f5.6, large > enough to get the backdrop nice and soft... Outdoors or anywhere where ambient levels compete with flash, what you say is true. However, if you are shooting manual flash ( a studio strobe) in a studio, and keeping the ambient light real low (not dark, just tungsten lit room), you can use any shutter speed as long as the shutter speed and aperture combination do not allow ambient light in the exposure, or very little. And so flash is dominating and thus controlling the exposure, so shutter speed is much less relevant. This is why a flash meter only registers aperture when I pop the flash to meter it. So, shutter speed is irrelevant in a studio, and most certainly won't affect DOF, only the aperture on the lens will affect DOF in this environment. Patrick >>>> Not necessarily preset, but limited. Some sets of strobes, like my >>>> cheap ones, have only a couple of stops of latitude in their settings [quoted text clipped - 24 lines] > > Patrick ?? On my flash meter, I set the shutter speed required, the meter matches that with the appropriate aperture, since all it can measure is the amount of light, not the speed of the shutter. There is an interconnection between the shutter speed and the aperture, and, while shutter speed is less important in the studio than in the field, because of the ease of controlling the light, you still need to be able to change the shutter speed to compensate for the aperture. If the fastest available shutter speed is 1/200, it is hard to get to f2.8 with strobes that only have a range of 2 stops. SignatureSkip Middleton http://www.shadowcatcherimagery.com > ?? On my flash meter, I set the shutter speed required, the meter matches > that with the appropriate aperture, since all it can measure is the amount [quoted text clipped - 5 lines] > 1/200, it is hard to get to f2.8 with strobes that only have a range of 2 > stops. I'm sure this is not news to you Skip: In flash work, aperture controls both flash and ambient light, but shutter speed contols _only_ ambient light. This is why, for most flash photography where ambiient is not desired, that the max sync speed is used. (And the beauty of leaf shutters with studio strobes). If your studio strobes have limited control (like mine) then you sew extra softbox difusers, bounce the light off of white cardboard, use ND's or slower film to get those fat apertures... My flash meters (Minolta VF and Sekonic 508 and 558) have a "ratio" reading for flash v. ambient. For most studio work, the ratio is 100% flash, but if you reduce the shutter speed enough, then the flash content drops (of course). Cheers, Alan. Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. >> ?? On my flash meter, I set the shutter speed required, the meter >> matches that with the appropriate aperture, since all it can measure is [quoted text clipped - 26 lines] > Cheers, > Alan. One thing I forgot about was ISO 50 on the 5D, that would get me an extra stop on the aperture. I'll have to try that. Part of my problem, besides the limited control, is the size of my "studio." It's my 11'x14' family room. Not enough room for a lot of devices. That, and I'm learning on the run... SignatureSkip Middleton http://www.shadowcatcherimagery.com > One thing I forgot about was ISO 50 on the 5D, that would get me an extra > stop on the aperture. I'll have to try that. That's a great advantage. A year or so ago I was at one of the stores I frequent and a Nikon oriented pro was looking at the Canon 20D (IIRC) because he needed the ISO 100. He had a D70 but the ISO 200 was causing him aperture fits with fill light. I kept my yap shut about ND filters <g>. > Part of my problem, besides the limited control, is the size of my "studio." > It's my 11'x14' family room. Not enough room for a lot of devices. Hmm, my studio, 14x14x14 is being converted into a "living room" at the insistance of my SO ... Additional point: damping the light of an Auto or TTL flash (with say a white cloth) does not work (unless it is in manual mode) as the system will pump out more light to overcome the dampening. With manual strobes or studio strobes, it works perfectly, of course. Cheers, Alan Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. > ?? On my flash meter, I set the shutter speed required, the meter matches > that with the appropriate aperture, since all it can measure is the amount [quoted text clipped - 5 lines] > 1/200, it is hard to get to f2.8 with strobes that only have a range of 2 > stops. That doesn't make sense. For flash exposure the shutter speed is unimportant; exposure will be the same at 1/125 as at 1/250 or 1/60, with the same aperture, unless ambient light is also contributing. Getting f/2.8 with strobes has nothing whatever to do with the shutter speed. SignatureJeremy | jeremy@exit109.com >> ?? On my flash meter, I set the shutter speed required, the meter >> matches [quoted text clipped - 15 lines] > the same aperture, unless ambient light is also contributing. Getting > f/2.8 with strobes has nothing whatever to do with the shutter speed. Like I said earlier, I'm still learning this part, not real experienced with studio strobes. I'll try that, next time. SignatureSkip Middleton http://www.shadowcatcherimagery.com > Like I said earlier, I'm still learning this part, not real experienced with > studio strobes. I'll try that, next time. With strobes, the exposure time is irrelevant because the exposure time is determined by the flash, which is (necessarily) of shorter duration than the actual shutter speed. You can set any speed up to the camera's maximum sync speed, and it doesn't matter in terms of exposure; the reading on the light meter for aperture is all that matters. The meter has a shutter speed indication because it also measures ambient light and determines the amount of contribution it makes to the overall exposure. Shutter speed does matter for any ambient light, of course. In a typical studio setup, the ambient light contribution will be zero. My meter indicates this by saying "100%" for the flash contribution. Decent studio strobes will shut off the modeling light when they flash, so even those won't affect the image. (What's interesting about that is that it's too fast to see; I "know" mine shuts off the modeling light because it says it does, but I never actually noticed it. I'd imagine that you could use a slow enough shutter speed to catch the modeling lights on; obviously the power pack has no idea what your shutter speed is set for.) Older flash meters like the ones I learned with don't have any shutter speed setting or indication because they measured only the flash. SignatureJeremy | jeremy@exit109.com >> Like I said earlier, I'm still learning this part, not real experienced >> with [quoted text clipped - 6 lines] > sync speed, and it doesn't matter in terms of exposure; the reading on the > light meter for aperture is all that matters. Ok, I get that, now. I took a lighting class a few years ago, but didn't use strobes then, and that part of the class didn't penetrate, apparently. But it's coming back to me, as I read what you wrote. > The meter has a shutter speed indication because it also measures ambient > light and determines the amount of contribution it makes to the overall [quoted text clipped - 8 lines] > lights on; obviously the power pack has no idea what your shutter speed > is set for.) That makes sense, now. My meter does that, too. I'm guessing that my strobes do, too, but I've no confirmation of that. OTOH, the modeling light is so weak that I'm not sure what difference it would make. It's about 100 watts. > Older flash meters like the ones I learned with don't have any shutter > speed setting or indication because they measured only the flash. I just started using strobes late last year, it's not something I'm familiar with, obviously. When I started working with studio stuff, strobes were out of my budget, so I stuck to floods. The price has come down, and my budget has gone up to meet it, but I appreciate the help. I have a shoot coming up that I'll put this to use for. Thanks, SignatureSkip Middleton http://www.shadowcatcherimagery.com >>Like I said earlier, I'm still learning this part, not real experienced with >>studio strobes. I'll try that, next time. [quoted text clipped - 4 lines] > sync speed, and it doesn't matter in terms of exposure; the reading on the > light meter for aperture is all that matters. Not quite. Most recent meters calculate the flash to ambient ratio. So if the shutter speed is slow enough you will get overall exposure as well as an indication of the contribution from ambient in the shot. > The meter has a shutter speed indication because it also measures ambient > light and determines the amount of contribution it makes to the overall [quoted text clipped - 11 lines] > Older flash meters like the ones I learned with don't have any shutter > speed setting or indication because they measured only the flash. You're missing the point of the % indication when used with flash. It is sometimes desirable to include ambient light with flash light, and the % indication allows you to figure the conribution from each source. As to shutting off the modeling lights, that's irrelevant for most studio shooting, typically at 1/500 (or at least 1/250 for a high end SLR) as the ambient contribution from a few watts of tungsten (eg: 1/500s X 200 W = 0.4W-s) v. the 100's W-s of flash power will not record on the film at all. For 1/60 shots, it may be a bit more useful, but again, the contribution v. the strobes is probably far too little to record. Cheers, Alan Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. >> ?? On my flash meter, I set the shutter speed required, the meter >> matches [quoted text clipped - 15 lines] > the same aperture, unless ambient light is also contributing. Getting > f/2.8 with strobes has nothing whatever to do with the shutter speed. That is precisely what I was stating. Patrick > The relevance come in when you are working in the studio with strobes, and a > faster shutter speed would allow you to lessen your depth of field. Studio strobes don't have HSS. You charge them to the energy level required and they dump completely (opposite of TTL/E-TTL flashes that are fully charged and dump down to a point cut off by the thyristor under command of the camera exposure system). You can dial your strobes down and/or put covers over them to lessen the light output and/or add ND's to the lens to get those fat aperture shots. Cheers, Alan Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. >> The relevance come in when you are working in the studio with strobes, >> and a faster shutter speed would allow you to lessen your depth of field. [quoted text clipped - 9 lines] > Cheers, > Alan Thanks, like I said, I'm still learning on the run with some of this stuff... SignatureSkip Middleton http://www.shadowcatcherimagery.com > I've been plowing through an online "book" on Canon EOS Flash Photography > http://photonotes.org/articles/eos-flash/ (OK - it's really just a web page, [quoted text clipped - 26 lines] > > Would be interested to hear peoples thoughts. direct flash is not the most pleasant light, and with high shutter speeds you get the equivalent of a coal miner's point of view, whatever is directly infront of you is brightly lit, everything else is black. somehow I don't think that HP sync works with slaved flash so you won't get any key fill light. I've always worked the other way around, slow shutter speeds, nearly wide open lens, minimal flash power, camera on a tripod, so the background gets to build up, I have a properly exposed subject with enough background to give the image some detail and depth. this reply is echoed to the z-prophoto mailing list at yahoogroups.com > somehow I don't think that HP sync works with slaved flash so you won't > get > any key fill light. It works fine with the ST-E2 Transmitter and 580EX Flashes. It's a setting on the transmitter - you don't even have to adjust the 580s. As far as I can tell, High Speed sync shrinks the guide number exponentially as shutter speed exceeds X sync. I have found it useful only when the subject is close to the camera. On wide angle shots in the sun, you could wind up with very little fill flash, not as much as you could have achieved with regular flash. What I would love to see is a leaf shutter as rugged and fast as a focal plane shutter. Now we could get some serious bokeh with our fill flash. Wouldn't that be nice? Patrick > Hi all, > [quoted text clipped - 6 lines] > for some reason I had it in my mind that High Speed Sync (or FP Mode) was > vastly inferior, and was likely to get poorly metered results. High Speed synch is useful in somewhat limited situations, and because only part of the film/sensor plane is exposed any one time, highly inefficient, draining the flash batteries very quickly while affording only short flash to subject range, and at that with the widest apertures. That last bit is okay, as the typical use of HSS is when there is a lot of ambient light and a wide aperture is desired for creative purposes. This could over expose at synch limited speeds, so HSS allows shooting at high shutter speeds and not over exposing the ambient, while getting fill and/or "freeze" from the HSS. I've used HSS from time over the past 8 years or so, but rarely has it really been needed or produced wonderful results. A set of ND filters can get a wide aperture shot down to sycn speed (may present a vignetting problem unless your sensor is "cropped") The Nikon D70's sensor based 1/500 synch speed is a wonderful solution, and much better than HSS, IMO. Cheers, Alan Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. > A set of ND filters can get a wide aperture shot down to sycn speed (may > present a vignetting problem unless your sensor is "cropped") I think another penny just dropped ... I've been thinking that ND filters are a thing of the past, but now that I think about it, if you're in a situation (say an outdoor wedding on a bright day with a very 'reflective' bride in white) where you want to use fill flash - you don't want to use HSS mode - and you don't want a large DOF then ND filters are the only way you're gunna get your speed below X-Sync? Cheers, Colin >> A set of ND filters can get a wide aperture shot down to sycn speed (may >> present a vignetting problem unless your sensor is "cropped") [quoted text clipped - 11 lines] > > Colin That same penny dropped, here. Excellent suggestion, and an easy solution. SignatureSkip Middleton http://www.shadowcatcherimagery.com >>A set of ND filters can get a wide aperture shot down to sycn speed (may >>present a vignetting problem unless your sensor is "cropped") [quoted text clipped - 6 lines] > flash - you don't want to use HSS mode - and you don't want a large DOF then > ND filters are the only way you're gunna get your speed below X-Sync? The white dress should not expose improperly at EV 15 (sunny 16) in the sun. The usual problem with the white dress is the metering of it, not the recording of it. Incident metering is best in this case, or at least meter the brightest white and then open up 2 to 3 stops (color negative film. If you're shooting 160 at 100, then 2 stops should suffice). But indeed, if you want fill flash and/or a large aperture, and esp. if the 400 (from the church ceremony) is still loaded, then one recourse is the ND filter. I carry 2 and 3 stop 72mm filters in my bag giving me the flexibility to adjust. It doesn't happen all that often, but it does happen. In the studio too, esp. with my limited strobes (1/1, 1/2) it's neccesary to have them. Cheers, Alan Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. >The only limitation I hit was the 580EX not being able to cycle fast enough >when I fired a burst of shots. There is another limitation, which can be quite serious when trying to stop action. If you are set to 1/320, etc, the duration of the flash can be many times as long as it is with normal sync, so 1/320 can give much more motion blur *and* possibly staggered into vertical strips) than with normal sync (which can be as fast as something like 1/10000). After all, HP sync is merely a strobe that lights the scene for as long as the shutter is open; not a single pulse of light that illuminates the frame all at once. >With this in mind, it begs me to ask the question: "Is an X-Sync speed of >"this" or "that" simply irrelivant in this day and age? >Additionally, can anyone think of a reason why Canon couldn't even give us a >custom function that says "Use FP Mode when >1/250 of a Sec"? I don't know about the 580EX, but the 550EX works just that way. It only uses high-speed sync if it is enabled on the flash, *and* the camera is set to a fast shutter speed. If the flash is on, but high-speed sync is not, then the camera won't honor your chosen shutter speed, and give you the normal sync speed instead. If high-speed is on, and the shutter speed is less than the sync speed, then normal sync is always used. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< > In message <v55rf.10307$vH5.501137@news.xtra.co.nz>, > After all, HP sync is merely a strobe that lights the scene for as long > as the shutter is open; not a single pulse of light that illuminates the > frame all at once. I was thinking that the strobing wouldn't necessarily have to continue for the full duration of the shutter opening, but thinking about it I can now see that it would have to (another penny dropped!). Am I correct in assuming that the X-Sync speed is really nothing to do with timing per sec - it's simply the fastest speed that both shutter curtains are fully open for the complete duration of the exposure? I know that the flash is cycled at around 50,000 times per second, but can anyone tell me if the "brightness" is adjusted by changing the flash intensity, or by changing the on-time -v- off-time in each 1/50,000 cycle? Cheers, Colin >>In message <v55rf.10307$vH5.501137@news.xtra.co.nz>, > [quoted text clipped - 8 lines] > simply the fastest speed that both shutter curtains are fully open for the > complete duration of the exposure? Yep. For bonus points, a front sync will fire when the first curtain is fully open and a rear sync will fire immediately before the rear curtain begins closing. This is important to record movement trails (ambient light) on moving subjects before "freezing" the subject. > I know that the flash is cycled at around 50,000 times per second, but can > anyone tell me if the "brightness" is adjusted by changing the flash > intensity, or by changing the on-time -v- off-time in each 1/50,000 cycle? In HSS, it does cycle. In normal mode it is DC. The actual rate is manufacturer / model dependant. The duty cycle (% of time on and off of the 50,000 Hz pulses) determines overall brighness for HSS. The duty cycle may change with HSS shutter speed, I don't really know but that would be a good assumption. For normal thyristor shutoff flash (normal TTL), it discharges at full power and current and then keeps discharing at lower and lower power until the thyristor cuts it off or until drained. Cheers, Alan Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. > I know that the flash is cycled at around 50,000 times per second, but can > anyone tell me if the "brightness" is adjusted by changing the flash > intensity, or by changing the on-time -v- off-time in each 1/50,000 cycle? Flash intensity is set by the on-time anyway, so both possibilities are the same. -Wolfgang > Hi all, > [quoted text clipped - 28 lines] > > Would be interested to hear peoples thoughts. It sure does on my large-format, medium-format, and 35mm gear. Also, with the D70, it's possible to create some really weird artifacts pushing the sync to its limit (1/8000 of a second, baby). SignatureRegards, Matt Clara www.mattclara.com |
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