CLS on D50
- Thread starter owrwe
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mmm... ok. Maybe i got it wrong?
for how long does a flash last? what's the duration of a flash, i.e. for how long is the lamp lighted? do i need to keep the camera shutter opened during that time for me to get a good shot? or do i need to open the shutter longer than the flash duration?
Am referring to the manual flash on my D50.
for how long does a flash last? what's the duration of a flash, i.e. for how long is the lamp lighted? do i need to keep the camera shutter opened during that time for me to get a good shot? or do i need to open the shutter longer than the flash duration?
Am referring to the manual flash on my D50.
kniveswood
Member
Dont worry about it bro, i cant recall the exact number but it's very very fast. Somewhere in the region of 1/10,000 if i remember correctly.owrwe said:
I believe there is flash sync speed limit on cameras is becoz of TTL. But dont quote me, just my assumption.
It's easy to do a test. Just shoot in absolute darkness with various shutter speeds and see if there is any difference. It's important to be absolutely dark overwise ambient light will affect the shots.
gooseberry
Senior Member
The flash duration is dependant on the output power the flash is fired at. I think the specs for the SB-600 are that the flash duration ranges between 1/900s and 1/25000s (something like that, may not be exact figures) where 1/900s is flash at full power and 1/25000s is flash at 1/64 power.
gooseberry
Senior Member
_espn_ said:I blur liao.. what do those figures mean?
A typical electronic flash works by discharging a high voltage of electricity through a tube of xenon gas to produce an instantaneous 'flash' of light. The duration of this flash of light is typically around 1/1000s (depends on the construction of the equipment etc). Flashes with variable power (a Nikon Speedlight for example) cut-off the electrical discharge before it completes (ie. at earlier times) to produce the lower power output levels (eg. 1/2, 1/4, 1/8, 1/16 etc power)
Correct :thumbsup: . That's for flash's Manual mode.gooseberry said:
If you use flash iTTL mode or AA mode, the flash will cut its duration when the flash think the subject is well iluminated (by flash). Result in flash duration between 1/900s to 1/25000s (not exact figures, following above example).
The flash's duration will not follow camera's speed!
Regards,
Arto.
kniveswood
Member
Nope, there's really nothing to worry about if you use TTL. Just keep within your body's flash sync speed._espn_ said:Okie, good for you, I'm still stumped, anybody care to explain to me?
Errr.....,kniveswood said:
Actually, the flash sync speed limit on cameras (SLR and/or dSLR) is not because of TTL. IIRC, it is the design of mechanical shutter and the sensor electronics shutter on the camera (that expose light to the film/sensor, according to shutter speed time period).
Regards,
Arto.
kniveswood
Member
Ahh..thanks for the explanation. I did read before that if you flash above the flash sync limit, you'll get black shadows in your images that are due to that mechanical shutter thing not moving away fast enough. I thought it had something to do with TTL.Artosoft said:
AFAIK, it is not the mechanical shutter thing not moving away fast enough, but because the mechanical shutter thing is creating window smaller than frame in order to exposure film/sensor 'faster than flash's sync speed' correctly (if above flash's sync speed and not for flash photography), so the flash illumination is not on entire frame and will be black somewhere (not always on the bottom, but in many cases is on the bottom).kniveswood said:Ahh..thanks for the explanation. I did read before that if you flash above the flash sync limit, you'll get black shadows in your images that are due to that mechanical shutter thing not moving away fast enough. I thought it had something to do with TTL.
After I think again, I did a mistake, the SLR's flash sync is mechanical one, I am not sure about the dSLR's flash sync, whether is mechanical only, or mechanical and electronic one.
The high speed flash's sync is achieved by strobing the flash, so the flash's strobe will illuminate few times (with syncing of course) through shutter's 'smaller window than a frame' that moving from top to bottom (or vice versa) to illuminate the film/sensor for shutter speed higher than flash's sync speed.
Somebody please correct me if I am wrong.
Regards,
Arto.
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