Using Flash to FREEZE the Subject.. what it means ?

[niranjan]

Hi,
As i understand the motion blur is reduced or omitted and the moving subject is made to look still by using faster SHUTTER SPEEDS.
But how the motion is made freeze using FLASH ? what actually that means ?

 

[Solarflare]

-

 

[enzodm]

Solaflare: in general (but not always), shutter speed when using flash is limited due to synchronization limits (e.g., 1/250s).

However, the flash lamp lasts for a very short time (thousandths of seconds), so if you are shooting in a relatively dark scenario, independently from shutter speed, your subject will be "seen" by the sensor only for the time it is being illuminated by the flash - much less than shutter speed. This freezes the subject.
When using flash, shutter speed is used to control background exposure more than subject exposure.

 

[SCraig]

The duration of the pulse of light from a flash is in the order of 1/10,000 second. If you are using a flash AND if the ambient light is low enough (or can be made low enough through the use of shutter and aperture) that it does not provide enough light to expose the image then the short pulse of light from the flash will effectively freeze the image. If the ambient light is sufficient to add to the exposure then you will get something in between, normally a partially blurred image.

 

[KmH]

Hot shoe speedlights at full power have flash durations of around 1/1000. As speedlight power is reduced, the duration of the flash of light gets even shorter. Nikon's SB-600, SB-700, SB-800, and SB-900 have to be turned down to 1/16 power to shorten the flash duration to about 1/10,000 of a second.

 

[Stradawhovious]

This.

I took this with two speedlights, very little ambient light and a shutter time of 1/60th of a second. Without the flash (and with sufficient ambient lighting) at 1/60th of a second the water droplet would just be a blur. The flash effectively gave me a much better vehicle to "freeze time" and get the action I wanted.

 

[niranjan]

so looking at Stradawhovious shot..
can i say that in low ambient light, moving objects can be freezed to still with using flash and no need to go for very high SHUTTER SPEEDS ?

 

[Infidel]

Yes.

 

[Stradawhovious]

so looking at Stradawhovious shot..
can i say that in low ambient light, moving objects can be freezed to still with using flash and no need to go for very high SHUTTER SPEEDS ?

Exposure time for this one was 6.1 seconds. I'll let you see if you can guess how I did it.

 

[gsgary]

Flash gives you more light, thus allows you to use faster shutter speeds.

False

 

[gsgary]

This was shot outside at 1/125 but my studio flash was not quite fash enough to freeze the action

 

[enzodm]

so looking at Stradawhovious shot..
can i say that in low ambient light, moving objects can be freezed to still with using flash and no need to go for very high SHUTTER SPEEDS ?

and you cannot use flash AND have very high shutter speeds together (except with a trick -high speed sync- available with some flash).

 

[Josh66]

so looking at Stradawhovious shot..
can i say that in low ambient light, moving objects can be freezed to still with using flash and no need to go for very high SHUTTER SPEEDS ?

The flash duration at lower powers is much, much shorter than the shortest shutter speed available on most cameras (typically 1/4000th or 1/8000th).

When you really need to freeze action, use the lowest flash power that will give you the exposure you want. Don't use the flash's auto mode, because that will select the highest power flash that will give you a good exposure (which will have a longer duration).

If you were in complete darkness, the shutter could stay open forever and you would never get an image. Whatever the flash duration is effectively becomes your shutter speed. 1/4000th would not be able to freeze action like you see in Strad's photos, but 1/50000th sure as hell can.

You just have to make sure the ambient light level is low enough that it won't affect your exposure.

 

[Stradawhovious]

^^^^^^

This. Good explaination... very accurate.

 

[niranjan]

and you cannot use flash AND have very high shutter speeds together .

what are the typical results ? underexposed and totally blackout shots?