using flash to freeze motion

[keanne0)))]

i like taking night shots and tonight i'm meeting up with my friends to kick the soccer ball around. i want to try and take some shots with flash and i have some questions.

i'm trying to go for the effect where the lights in the background are kind of blurred but the subject be sharp in focus. i took a few last time and got undesired results:

1 second, f5.6, ISO 200

i'm not used to shooting moving things at night so any pointers would be much appreciated. also, how should i meter shots like this using flash? should i set the exposure as if i weren't using flash or should i underexpose it to compensate for the flash? thanks

 

[tirediron]

First of all, are you using the built-in flash or an off-camera flash? You'll need some definitive advice from a Canon user, but I suspect the built-in flash may not be strong enough to shoot these images from any distance. That aside, I would recommend using aperture priority reasonably wide open and shoot a couple of test images. The flash should freeze all movement nicely, the large aperture will give you a soft background, and you can see whether you need increase or decrease your flash strength.

 

[keanne0)))]

thanks for the response. yea i'm using a built-in flash. how do i increase or decrease flash strength? and also, 1/200 sec is the fastest my shutter speed will go with flash; why is that?

 

[Garbz]

Flash sync. The picture is taken with 2 curtains racing across the frame letting light in. Above 1/200 the front curtain is not yet at the other side of the frame before the rear curtain starts closing and thus if you take a photo the flash would not be visible in the entire picture.

Few tips. This rarely works well with such a bright light source in the frame. Try to not shoot into the streetlight. Also the flash exposure depends on the camera. The D200 has a flash compensation button to boost or dim the flash, for another camera I'd have to say you need to read your manual.

 

[Big Mike]

Flash photography is basically two exposures at once. The first is from ambient light (from street lights, for example) and the 2nd is from flash. The ambient exposure is controlled by the shutter speed, the aperture of the lens and the ISO. The flash exposure is controlled by the aperture of the lens, the ISO and the flash output (not the shutter speed). This is because the flash burst is very quick, much faster than the shutter speed.

In a situation like yours, I would suggest putting the camera into manual (M) mode. This is because in all the other modes, the camera's meter will try to expose for the ambient light, which is quite low. That is not what you want.

Start with settings like F5.6, 1/125 and ISO 200. That will probably underexpose the ambient light, making the background dark...but the flash should light up the subject and freeze any motion.
You can change the shutter speed setting to change how much ambient light will be recorded. A longer shutter speed will give you more ambient exposure and can also give you blur. Experiment with different speeds to see what you like.

A certain amount of ambient light on the subject can also cause blur when the shutter speed is slow, and the flash exposure may or may not be strong enough to give you a sharp image over top of that. Again, experiment as see what works.

You might also want to go into the menus & custom functions and set the flash to 2nd curtain sync.

 

[391615]

I did this for the first time the other day with good results.

use the second sync flash, set it in manual for 1 second, pan the camera and time the second flash to the area you want in focus with the flash. Up the flash ev and up the ISO if need be, trial and error usually works.

It works well with sunsets, and you can also experiment with swirls and different blurring movements. you can also warp shots changing the focal length, they look pretty cool.