freezing motion in the studio

stumac

stumac

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stuart
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Hope you can help,I was under the impression when using flash of any kind that regardless of your shutter speed it was the flash that froze any movement and in fact the flash duration was actually your shutter speed.....i was taking some shots of the kids in the studio and there was a couple of my daughter 1- waving at me and her hand came out a blur 2-she was spinning around quite slowly but again she came out a blur(motion blur not out of focus)
where have i went wrong?
settings were 1/125 f8
 
the flash does indeed freeze the subject but the speed of the flash may be the issue. Expensive flashes have a t5 of about 1/4000th sec. Cheaper units maybe around 1/1000th but that may not be fast enough to freeze fast moving hands.
 
It's the lencarta smart flash heads I've got
 
t.5 is described better here
http://www.scantips.com/speed2.html

I know Garry Edwards knows this stuff (a little over my head) but seems real speed is around 1/3rd of the t.5 so in your case if you have the 200s then closer to 1/600th

So you can see why you get blur.
 
Scarecrow said:
Ambient light may also be a factor. If it's bright, it may be enough to allow the movement to be recorded.
Click to expand...


Edit - Thinking about this I can see yes I can see your point.
 
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It could be ambient light blur if there's bright daylight coming through, but normal room lights won't have any effect.

It's more likely to be the flash duration, which is your effective shutter speed as you say, but TBH the t.5 figures that most manufacturers publish are frankly a lie - but they use them becuase they're an industry standard that makes them look better.

From my tests comparing flash durations to actual shutter speeds, as a very rough rule of thumb the visual effect in terms of 'action stopping potential' is somewhere around 2x the t.5 time, possibly up to 3x which is where the t.1 time usually sits.

More general rules of thumbs - effective flash durations will usually be shortest at full power with a studio head. But can vary, especially with battery packs, depending on how the capacitors are configured. Manufacturers' literature should be a decent guide on this.

For the shortest flash durations, hot-shoe guns are much better because of the way they clip the flash pulse at reduced output (good link posted above). Typically, you'll get a real 1/1500sec at half power and it gets shorter and shorter as output is reduced, down to 1/40,000sec in some cases.

One thing that generally distinguishes expensive studio heads from entry level kits is the shorter flash durations.
 
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