Posted by Ryan Askren on March 11, 2009 at 4:55 PM
I recently bought a Nikon SB-900 flash unit and could use some help using it. By biggest problem right now that the flash/shutter speed aren't quick enough. What mode should I be shooting? I was also using it in sync with a SB-600 for water droplets and was having this problem. I would also appreciation any other info on what I should be doing with it for widlife (birds). Thank you for helping and tolerating the newbie.
Posted by David Bostedo on March 11, 2009 at 6:05 PM
I'm not sure what you mean by "using it in sync" Ryan, but what you're likely running into is a max sync. speed issue. Depending on what camera you're using it on, the max. shutter speed you can typically use is limited to somewhere between 1/150th and 1/500th of a second - most likely around 1/250th.
So usually, even if you try to take a photo at a faster shutter speed, say 1/1000th, the camera will slow it down. Your camera and flash probably have a high-speed sync mode, which will allow faster shutter speeds, at the cost of losing flash power. Look in your manual for it.
As far as flash use for wildlife, I can't give any advice other than learn manual flash control in addition to TTL, and try googling - there are lots of pages. I'm sure others here will have advice.
Good luck!
Side note : The reason your sync speed is limited is the flash duration is VERY short, much quicker than your shutter speed. So the shutter has to be fully open when the flash goes off. At speeds faster than about 1/250th, the shutter is actually never fully open (it can't open and close fast enough). Instead, the two parts of the shutter only allow a slit to be open, which moves across the sensor/film, so that each part is exposed for a very short amount of time.
For high speed sync, the flash is pulsed so that it's duration is as long as it takes the shutter to traverse the sensor/film. That's why you lose power.
That's also why P&S cameras without a shutter actually have higher sync speeds than pro SLRs. No problem with the shutter having to open and close.
Posted by Dan Borzynski on March 11, 2009 at 7:29 PM
Could you elaborate on what you are trying to do with the water droplets? Setup, indoors, outdoors, faucet, etc.
I am going to assume that you are trying to get water droplets indoors and make a guess as to what you are doing.
For water droplets, 1/250 sec for a synch speed is more than fast enough. The duration of the flash output is actually quite short - a lot less than /250 sec.
The problem that *might* be occurring is that you are working in a room with a relatively large amount of ambient light and are trying to get the shot with a fast shutter speed. What will happen is that as you exceed the synch speed of the camera, you will get a bunch of very short flashes to fully illuminate the subject, at various points in time as the shutter is open (as David more clearly describes). The tradeoff, though, is that the power is reduced significantly, which is what allows all of those multiple quick bursts. You then wind up with a flash that is not putting out enough light to overpower the ambient light.
What you need to do is to take the setup into a darkened area, or repeat it at night with most of the lights off. The 1/250 synch speed, with the flash, should work in now, without having to try to overpower the ambient light.
Of course, this may not at all be what you trying to do and basically irrelevant.
Posted by Kent Staubus on March 12, 2009 at 7:36 PM
Flash--finally something I have recently learned a bit about. For the birds, get a Better Beamer. Be careful to keep it out of the sun when not in use. People have been known to casually set one of these on the backseat of their car, sun shines through it and it burns a hole in the seat like a magnifying glass would.
To do the water drop thing, you need to be in a nearly dark room. Flash must be set fairly close to water, set to something like 1/16th or even 1/64 power. Sync/shutter speed won't matter. At such low power levels the capacitators dump the charge at something like 1/10,000 second. Doesn't work that way with a monolight though, just the small 4AA type flash like you have.
Discussion
3 repliesSo usually, even if you try to take a photo at a faster shutter speed, say 1/1000th, the camera will slow it down. Your camera and flash probably have a high-speed sync mode, which will allow faster shutter speeds, at the cost of losing flash power. Look in your manual for it.
As far as flash use for wildlife, I can't give any advice other than learn manual flash control in addition to TTL, and try googling - there are lots of pages. I'm sure others here will have advice.
Good luck!
Side note : The reason your sync speed is limited is the flash duration is VERY short, much quicker than your shutter speed. So the shutter has to be fully open when the flash goes off. At speeds faster than about 1/250th, the shutter is actually never fully open (it can't open and close fast enough). Instead, the two parts of the shutter only allow a slit to be open, which moves across the sensor/film, so that each part is exposed for a very short amount of time.
For high speed sync, the flash is pulsed so that it's duration is as long as it takes the shutter to traverse the sensor/film. That's why you lose power.
That's also why P&S cameras without a shutter actually have higher sync speeds than pro SLRs. No problem with the shutter having to open and close.
I am going to assume that you are trying to get water droplets indoors and make a guess as to what you are doing.
For water droplets, 1/250 sec for a synch speed is more than fast enough. The duration of the flash output is actually quite short - a lot less than /250 sec.
The problem that *might* be occurring is that you are working in a room with a relatively large amount of ambient light and are trying to get the shot with a fast shutter speed. What will happen is that as you exceed the synch speed of the camera, you will get a bunch of very short flashes to fully illuminate the subject, at various points in time as the shutter is open (as David more clearly describes). The tradeoff, though, is that the power is reduced significantly, which is what allows all of those multiple quick bursts. You then wind up with a flash that is not putting out enough light to overpower the ambient light.
What you need to do is to take the setup into a darkened area, or repeat it at night with most of the lights off. The 1/250 synch speed, with the flash, should work in now, without having to try to overpower the ambient light.
Of course, this may not at all be what you trying to do and basically irrelevant.
To do the water drop thing, you need to be in a nearly dark room. Flash must be set fairly close to water, set to something like 1/16th or even 1/64 power. Sync/shutter speed won't matter. At such low power levels the capacitators dump the charge at something like 1/10,000 second. Doesn't work that way with a monolight though, just the small 4AA type flash like you have.
Kent in SD