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Q. Flash Synch? Metering with Flash?
Asked by James McGinnis
(K=6045) on 7/21/2004
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I've heard about "flash synch" being better with leaf shutters but....what the heck difference does it make? Could anyone give me a quick tutorial on this?
Also, I was shooting some night shots with my bronny. I'm using a Sekonic L 508 meter and couldn't get the meter to read with the flash, nor could I get the flash to fire when I tripped the shutter. I've used it in the past, so I know the camera and flash "talk" to one another but I just couldn't get it to fire with the camera no matter what I did. I realize this is probably two questions in one but, how do you get the meter to read your flash and what are some of the common problems to look for when your flash won't fire?
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Peter Witkop
(K=3189) - Comment Date 7/21/2004
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Because of the way a leaf shutter works, at all speeds the shutter is completely open, so a leaf shutter will sync at all speeds. With a focal plane shutter at faster speeds, there isn't a time when both curtains aren't in front of the film plane, the sync speed for a focal plan shutter is the fastest speed when both curtains are not infront of the film plane a the same time. With a faster shutter speed, the flash will go off, but part of the frame will not recieve any flash exposure due to the shutter being infront of it.
As to what's going on with your flash/camera/meter, it's hard to venture a gues without knowing just what you're using for equiptment (other than the meter, I use the same one BTW), and just what you're doing, how everything is connected, etc.
Peter
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Adam E. J. Squier
(K=9803) - Comment Date 7/23/2004
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Peter covered the part about why syncing at faster speeds works. One of you questions was "what the heck difference does it make?"
Let's say you're shooting on a sunny day and your meter reading says f/8 @ 1/500. You decide to use the flash for fill (a very good idea, you think to yourself). If your fastest sync speed is 1/60, you'll need to stop down to f/16 or so. You may not want to use such a small aperture because you want to throw the background out of focus. So what do you do? You're stuck, unless you put a ND filter over your lens (if you have one handy). Now you need to adjust the flash output to compensate for the ND filter, but wait, the moment's gone. Too bad.
If your fastest flash sync speed is, say 1/500 (as it is for most leaf shutters and some SLRs), you won't have to skip a beat in your shooting. Make sense?
Now, about your meter. Are you connecting the flash to the meter with a long cord? Are you using the meter in wireless flash mode? Do you have a PocketWizard receiver hooked to the flash (and, of course, the transmitter in the meter)? These are three ways to get your meter to read the flash.
As far as problems with the flash not firing, I haven't had any problems since using a PocketWizard setup. Well, no problems with my flash not firing. ;-)
I'd strongly suspect the problem is with the sync cord you're using, assuming you're using a sync cord. I had so many problems with them it was worth the expense of the wireless PocketWizards. Not only do my lights fire every time, but there aren't any wires following me around.
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James McGinnis
(K=6045) - Comment Date 7/23/2004
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OK. The sych thing still confuses me. I'm just beginning to learn about flash lighting.
I get the meter vs flash stuff though. Actually, I have a Flash (c) setting on the 508 that worked perfectly well once I figured out that the flash had to be hooked up to the meter!!! But, I still don't know why the camera and the flash weren't working.
Today I bought another bronny body to use as a back-up. I'll try to use the flash with this new body to see if that's the problem.
Thanks for all the input. As I said, I'm still fuzzy on the synch issue. I may need it put in very elementary terms....This is your leaf shutter, this is your leaf shutter with a flash...really, really, really basic stuff....as if I don't know the first thing about cameras and flash set ups (That's probably not too far off the truth!!)
Thanks again!!!
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Raoul Endres
(K=2676) - Comment Date 7/24/2004
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Leaf shutters:
There are two things covering the film to keep it dark. The mirror and the shutter (which is in the lens).
When you press the shutter button, it releases the mirror, then after a short delay, it opens the shutter. shutter stays open, and then it closes and the mirror goes down. Simple.
See how this works with flash -> there is nothing blocking the film, when the shutter is open, so the sync rate is the shutter speed.
With focal plane shutters (SLR's):
You have the same set up, but the shutter is BEHIND the mirror. There are also TWO shutter curtains, that move in unison across the film. So in effect, at higher speeds (they can't move that fast), you have a moving strip of an opening, maybe half the size of the film.
What happens when you use flash, is that the flash will fire, but for that 1/10000th of a second, only half the film is visible. So you'd only illuminate half the film, the other half would be underexposed.
The flash sync rate here is the fastest speed at which the film is fully visible (ie: a speed slow enough that the camera maker didn't need to try fancy tricks to increase shutter speed.)
The flash sync rate for these types of camers is usually between 1/60th to 1/250th, with some high end cameras going to 1/500th.
High speed sync options on some flashes allow you higher speeds - this works by firing the flash for a much longer duration (longer than the shutter time), so the flash has time to illuminate the entier film as the two curtains move across it.
ok done typing now.
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Adam E. J. Squier
(K=9803) - Comment Date 7/24/2004
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Just for clarification, not all SLRs have focal plane shutters. 35mm format and similar-sized cameras usually do. I started that with my previous post.
Digital cameras (DSLRs) open up a whole other can of worms. They usually have a focal plane shutter, but can also "turn on" the sensor to expose it. So, for fast shutter speeds, the shutter curtains may be open for a longer time than the set speed, but the sensor is only "on" for the faster speed.
In effect, the sensor becomes the shutter. I believe (but I'm not positive) that this is how the Nikon D70 gets its 1/500 flash sync speed. Even with the sensor being smaller than 35mm, I still don't think the shutter curtains can move that fast. I could be wrong.
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James McGinnis
(K=6045) - Comment Date 7/25/2004
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Much clearer now! Thanks Raoul...that was just the level of elementary explanation that I needed!
Adam,
If you could, tell me more about the pocket wizard. I just found some info on them at home (came with the sekonic meter). Are they really worth the money?
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Adam E. J. Squier
(K=9803) - Comment Date 7/26/2004
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PocketWizards work extremely well. I've never had one not work. For me, they're worth it. I can't say for you. They aren't cheap. For the less expensive ones be prepared to spend $600 for a transmitter and two receivers (for two lights). The transceivers are more expensive.
If you can justify the expense, they're fantastic. I kept having the sync cords not work or the optical slave not work (usually if the sun was shining on it). Now, no problems.
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