Second Curtain Flash - Faking it with non-Canon Flashes

When you take a picture, there are two "curtains" that control access to the sensor, one that opens right when you hit the shutter and a second that closes, covering the sensor. Most of the time, if you are using external flash, the flash fires right as the first curtain opens. This is fine if you are using faster shutter speeds and your subject is relatively stationary. However, if you are using a slower shutter speed, it doesn't work as well - you can get odd looking ghosts - your subject will be in focus when the flash first fires and then there will be ghosting of the image as the subject moves, and then the second curtain closes off the sensor.

One way to mitigate this is to synch your flash with the second curtain. The ambient light burns into the sensor, exposing the background and then, right before the shutter closes, you flash your subject, getting a nice in focus subject.

Here's an exaggerated example. I am using a five-second shutter speed and small kids, even at the end of the day, right before bed, don't slow down much.

There is some ghosting, but it is leading up to the final moment. It can show movement in a more natural way, since the ghosting leads into the portion of the photo that is flashed and in focus. The area that was flashed good is nice and in focus.

I was triggering this by walking my flash over and focusing it on one spot - the bad part of this is if I dwelled in the frame, I show up a bit, like below (on the left portion of the photo):

Second curtain shutter can allow you to use a longer shutter speed to get a good exposure of a night/twilight scene and you can then flash your subject right at the end. With some practce (and unlike above) you can balance the light so the whole thing looks good. Hopefully I'll get there, just need more practice.

The trick is, I think you have to have the expensive Canon flashes to do this from the camera; I've got cheaper third-party flashes. But there is a way around this.

The Work Around

My flashes (and pretty much all external ones out there) all have a slave option. This means they can be triggered by the light from another flash. So what I did was use my on-camera flash as the trigger, since I can set this to fire in synch with the second curtain. In order to not have it impact the exposure, I powered it way down - 1/128th power. This is enough to trigger my slave sensor in my other flash.

I was able to sucessfully do this inside the house and also outside, under cover and in the shade. I'm not sure what kind of range I can use this, since the light from the on-camera flash drops off pretty quick. The good thing is that, in theory, I should be able to balance that out with my other external flashes. As I get more time to play around, I'll have to post some more trial photos.