Studio flash confusion

[Britman]

Hey,
I've been looking into trying some high speed flash, for water droplets and the like, but I'm still a little confused by the relationship between power settings of say a studio strobe and the shutter speed you can use.

As I understand it, the lower you set the power output the higher the shutter speed?

I'm thinking this is way too simplistic.

[sstalker]

Britman,

The shutter speed in this application is controlling the ambient light exposure and has little to do with the droplets. Just keep it at or below your max sync speed. The duration of the flash will determine how much "action stopping" you do on the droplets. For most flashes, the lower the power, the shorter the flash duration. The flash duration may be as quick as 1/30,000 sec.

Steve - Toledo

[Britman]

so if I keep the shutter at 1/250th and adjust the flash output to say 1/64th it will freeze the droplets?
I have tried it on full auto but always get blurring, I'm guessing this is because the flash lasted to long, like shooting at 1/250th in daylight?

[Wilt]

Terminal velocity of a 1mm water drop is about 4 m/sec. So with 1/1000 flash duration, the drop travels 0.004m or 4mm. Let that help you determine suitability of a given flash unit at a particular power level. a 2mm typical rain drop has terminal velocity about 6.5 m/sec

[Steve Wintrow]

if you are looking at studio strobes you should also consider a light meter. this is the easiest way to gage your settings. you can vary both the shutter speed and f stop depending on what you are trying to accomplish. you just fire your strobes and take a light reading with your meter and set the camera to those settings and shoot the picture.

[Curtis N]

I have tried it on full auto but always get blurring, I'm guessing this is because the flash lasted to long, like shooting at 1/250th in daylight?Full auto probably means the camera used 1/60 shutter speed.

You need to concentrate on two things:
1) Flash duration - With battery-powered flash units (such as your Sigma 500), lower power settings will give you shorter flash duration, which is what you want. The closer your flash unit is to your subject, the less power you need.
2) Ambient light - You want to eliminate the ambient light contribution to the exposure as much as possible. This means shooting in relatively dark environments and using X-sync shutter speed (1/200 or 1/250 depending on your camera). Using low ISO and small aperture can help with this too, but these will require more flash power.

[René Damkot]

One of the many Google hits on "photograph water drops":

http://www.popphoto.com/howto/2508/you-can-do-it-how-to-photograph-water-drops.html

[Jim M]

My general, but limited, experience with studio strobes is that their flash is much slower than camera mounted flash. Shutter speed is not a factor in the speed of flash illumination. It is only a factor if it lets in more or less ambient light than you want or if you exceed the sync speed. In your case, you don't want any ambient light. I would suggest using your camera on manual with the shutter speed at the highest sync speed of 1/250 with your 40D. I would set the aperture at f/16 or so, and ISO at 100. Then adjust the flash for a proper exposure. I would probably put everything on manual, including focus.