Some basic flash questions

[kirbinster]

My single weakest are is understanding the use of flash, so please bear with me regarding some simple questions.

On my Nikon D300 what exactly is flash shutter speed speed which goes from 1/60 th to much much lower and how does that compare and contrast to flash sync speed which goes from 1/60 th up to 1/320 th. Why is it that the maximum shutter speed that the popup flash will function at is 1/320 th, but when I use my SB-600 off camera I can shoot as fast as 1/8000 th?

[Sweetlifephoto]

Think of your shutter as two curtains the first one opens two the left and the second one closes behind it. At 1/60 or slower the entire shutter is open for a period of time so the flash fires and illuminates the entire frame so your flash operates properly all the way to a very long exposure like a bulb setting.

At faster shutter speeds the second curtain starts to close while the first one is still opening so it creates a gap that moves across the sensor. The faster the shutter speed the closer together the first and second curtain are and the smaller the gap that lets light hit the sensor.

If a flash fires only once during that time the portions of the sensor that are blocked by one or both of the shutters will be dark. So your SB flash has a high speed sync mode that actually fires the flash multiple times during the exposure to expose the light to the entire sensor as the gap travels across it.

Does that help or have I made it worse?

[kirbinster]

I think you lost me. When used off camera commanded by the popup on my camera does the SB-600 actually know what my shutter speed is -- I did not think so.

[RichardTaylor]

Re the high shutter speeds.

I am a Canon shooter, however this post may help.
Scroll down to "A better solution" - It covers both Nikon and Canon.

High Speed Sync for Flash at Any Shutter Speed

[sk66]

You've got "slow sync" which allows the aperture/SS to gather more "ambient light" and the flash will match as "fill" in A/S modes. The 1/60-1/320 is the "normal range" and the minimum value selected by the camera can be set in the custom menu (e3?).
The internal flash just doesn't have the power/ cycle speed to do higher sync speeds (auto FP).

[sk66]

Originally Posted by kirbinster

I think you lost me. When used off camera commanded by the popup on my camera does the SB-600 actually know what my shutter speed is -- I did not think so.

yes, it does...kind of. The camera knows and it sends a control signal to the SB to fire appropriately.

[kirbinster]

Originally Posted by RichardTaylor

Re the high shutter speeds.

I am a Canon shooter, however this post may help.
Scroll down to "A better solution" - It covers both Nikon and Canon.

High Speed Sync for Flash at Any Shutter Speed

Thanks, very interesting article.

[thebucch]

Great article.