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D700 with SB800 & SB900


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#1 Tony pepper

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Posted 27 August 2009 - 08:31 PM

I have a question that is not clear what the answer is. The D700 says you can use the SB 800 & SB900
at Shutter speeds of 1/250 and 1/320 of a sec. In Aperture Priority mode, you should be able to use these Shutter speeds.
The SB 800 and SB900 are variable and the flash can adjust for more or less power. So why in Aperture Mode do you only get
1/60th of a sec for Flash? I under stand in Manual Mode you can adjust this. But it would be nice to have a faster
Shutter speed with a powerful Speed light. I do believe you can do this in Shutter Priority Mode, but be nice to do this in Aperture
mode. any one have a clue why you only get 1/60th in aperture Priority Mode? Thank you for a responds and you can send it to
hotpeper9@yahoo.com


#2 justshootit

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Posted 28 August 2009 - 07:42 AM

It's trying to balance flash & ambient light, and there isn't enough ambient light for a shutter speed faster than 1/60th sec. This gets a little complicated, but I'll try to explain. In regular sync mode, the camera will, in aperture priority mode and program mode, use shutter speeds between 1/60th and the max flash sync speed for the camera -- from what you wrote above, I assume that the max sync speed for the D700 is 1/250th or 1/320th (is it 1/250th with the SB-800 and 1/320th with the SB-900?). Let's assume for the moment that you have an SB-800 and the max flash sync speed is 1/250th. Suppose you have a scene where you need to use f/8 and that has a non-flash exposure of f/8 and 1/30th sec at your chosen ISO -- with the flash off, you select f/8 and the camera will select 1/30th sec -- simple so far. When you turn on the flash in regular sync mode, the camera will then use 1/60th because that's the slowest shutter it'll use with flash. If you open up to f/4, then you'll see the shutter speed come up to 1/125th; open up to f/2.8 and it'll come up to 1/250th Open up to f/2 and you will still get 1/250th with an overexposure warning because the correct shutter speed is 1/500th, but this is faster than the camera's max sync speed of 1/250th. Lets fo back to our exposure of f/8 and 1/30th. If you turn on slow sync mode, then the flash will use 1/30th sec . In slow sync mode, the camera will use the shutter speed needed for an ambient light exposure, and use the flash as fill light. In other words, it'll use shutter speeds ranging from 30sec to 1/250th. However it will still not exceed the max sync speed. Try the following, select f/16 and ISO-200 and then use a scene that meters at a shutter speed below 1/60th with the flash turned off. When you turn on the flash, the shutter will default to 1/60th. Now start opening up the aperture one stop at a time and see what happens. Now try the same aperture but with ISO-3200 -- then vary the aperture. Then report back what happens...

Edited by justshootit, 28 August 2009 - 08:20 AM.

Don
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Digital: D610 backed up by a D1x.  Quoted from an unknown source by a fellow planeteer, "Never get rid of a working D1x." I've got to agree.

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#3 José

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Posted 28 August 2009 - 10:14 PM

Sounds good to me...great information here.
José

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