Need HELP stopping motion at night

[RichardTaylor]

Keep in mind I am not an expert.
When you are shooting with your flash you basically forget about available light and metering the scene for it, unless you are using slow sync flash or fill in flash.

The flash will be providing the light and (or pretty much most of it) and I feel the camera + flash metering system (ETTL) usually does a good job.

These pics were taken at home this morning. The blinds at one end were closed to make it fairly dark.
Canon 5D & Canon 580EX on camera flash was used. ISO was set to 400. Manual focus & using a self timer. Canon 24-70 F4 L IS lens
Second curtain Sync & ETTL evaluative were the camera flash settings - Custom functions.
Levels, resizing & sharpening done when PPing the RAW files

(1) Available light only (shot in manual mode with 1 stop deliberate over exposure.)

Exposure 1.3
Aperture f/4.0
Focal Length 35 mm
ISO Speed 400

(2) Available light only Manual mode with no deliberate over exposure (Basically the pic was under exposed and needed a fair bit of levels adjustment)
The main thing is that the "dancing me is blurry because of the slow shutter speed.

Exposure 0.3
Aperture f/4.0
Focal Length 32 mm
ISO Speed 400

(3) Flash (In ETTL mode and no flash exposure compensation)
Camera in P mode - Basically it is doing it's own thing.
Trying its best to expose for the ambient light but not go below 1/60, that's why the aperture is wide open, and doing the rest with flash - in this case 99% of it..
Notice the short duration of the flash has now "frozen" me.
It's not the 1/60 second doing that.

Camera Canon EOS 5D
Exposure 0.017 sec (1/60)
Aperture f/4.0
Focal Length 32 mm
ISO Speed 400
Exposure Bias 0 EV
Flash On, Fired

(4) Lastly just to show how a bounce flash helps with the lighting.
Flashgun pointed 45 degrees toward the 9' (3m) whitish ceiling with the catchlight panel extended. I forgot about the -1 exposure bias for the camera - I think that just darkens the background a little. Still in P mode.
I was still "dancing"


Exposure 0.017 sec (1/60)
Aperture f/5.6
Focal Length 32 mm
ISO Speed 400
Exposure Bias -1 EV
Flash On, Fired

Why not try something like this at home and see how you go. Basically the only extra you need is your tripod, if you don't have anybody to do the shooting.

[inkista]

Welcome to the wonderful world of flash-think.

The flash burst is far faster than your max. shutter speed. As long as a subject is lit only by the flash, the flash burst can do the action freezing for you, rather than the shutter speed (as Richard's photos admirably demonstrate).

Originally Posted by rickp1

[flashing]... I think, and anyone, correct me if I'm wrong, it's doing it because its not taking the flash into consideration when metering.

Yup. Remember, metering can only measure the light that's there. The flash burst isn't part of that amount of light. You're going to be adding the flash illumination to what you're getting with the ambient. And those two sources of light are more or less independent of each other.

Ambient illumination (usually your background) is controlled by three settings: your iso, your aperture, and your shutter speed. The higher the iso, the wider the aperture, or the longer the shutter speed, the more ambient light you're going to get in the image.

The flash illumination (usually your subject) is controlled by four things: your iso, your aperture, your flash output power, and the distance of the flash from the subject. Note how shutter speed isn't in there. This goes back to how fast the flash burst is: it's much faster than any possible shutter speed you can set, so the amount of light contributed is going to be the same whether you have a fast shutter speed or a slow one, if your other settings stay the same.

With flash: the higher the iso, the wider the aperture, the higher the power output, or the closer the flash is to your subject, the more flash illumination you'll have in the scene.

So, yes, you can use a lower iso or a faster shutter speed, or a smaller aperture if you compensate by bringing the flash in closer or increasing the flash's power output. But you always have to keep in mind that a speedlight is powered by mere AAs, and that there's an upper limit to how much light it can push out. Going to f/16, iso 100, and 1/500s with high-speed synch and shooting on continuous burst is a really easy way to heat up your flash. Increasing your iso, lowering your shutter speed, and opening up your aperture are all ways to ease the power draw on your speedlight. Using less power per burst can increase your recycle time, and keep your flash cooler.

Let me ask you something, am I not setting something right in the flash to maximize sync?

The "sweet spot" for shutter speed is to use the max. sync speed of your camera body (1/200s). Once you go faster than that, you're going to be needing high-speed sync, which can severely drain power and decrease light. Highly recommend reading this article on high-speed sync for the whys and wheretofores. But essentially, at 1/200s, the entire sensor can be lit by a single flash burst. Once you go faster than that, only a portion of the sensor is uncovered at any given time, and multiple synched flash bursts have to happen to illuminate the full frame. That's why you're going to be lowering the light and sucking extra power from your 580EX by using 1/250s vs. 1/200s on the 5DMkII. Which is probably why you had stuff flashing at you in the viewfinder.

[rickp1]

Guys,
Thank you for taking the time to illustrate the explanation, it's very much appreciated.

In the past I have heard about the flash freezing the action and in understand it to a certain extent.

This will help in improving my images, I just need to play with it some more and so more low light people photography.

Again thanks guys.

R.