Question About 2nd Curtain Flash

Hey guys,

I know what a 2nd curtain flash does and know that it is also used to capture some ambient light, but I had a question on a certain situation.

I took a picture of someone on a bridge with a nice fountain and a few lights in the background. I exposed for the person, therefore losing the fountain and lights. Would a 2nd curtain flash help me expose him correctly and get the fountain off in the distance? This was at night and I have to use at least ISO 1600 to get any of the lights to show. Wouldn't that have overexposed the subject? Sorry, but I don't have a picture to share.

Thanks for any help you can give!

Second curtain flash doesn't help capture ambient light.

What it does is orientate any movement captured by ambient light caused by a slow shutter speed.

A prime example is a moving train's headlights captured in a flash photo. With 1st curtain flash the lights would show an opposite movement to the car's direction because the flash occurs at the beginning of the exposure. . 2nd curtain flash would show the lights in the correct forward movement.

Thanks for the comment! I thought I read somewhere that it helped capture ambient light..guess not..is a double exposure the only way to capture a properly exposed background and foreground?

DavidSR wrote in post #6288401
Thanks for the comment! I thought I read somewhere that it helped capture ambient light..guess not..is a double exposure the only way to capture a properly exposed background and foreground?

If you are talking about a flash exposure, no.

A long exposure on a tripod will capture as much ambient light as you want.

DavidSR wrote in post #6288401
Thanks for the comment! I thought I read somewhere that it helped capture ambient light..guess not..is a double exposure the only way to capture a properly exposed background and foreground?

There is no 'double' exposure (analogous to two separate shots on the same piece of film) There are two components of the single exposure...the part created by the flash output, and the part created by the ambient light. To balance it, you control shutter speed. A short shutter speed could make everything come from the flash exposure. A slow shutter speed makes parts come from the flash and also the ambient light.

2nd curtain sync merely determines the ambient portion's position in time, versus the flash, but not how prominent.

What I meant was to do 2 single exposures and merge them together in post processing. Basically one shot exposed for the background and the 2nd shot exposed for the subject. Seems like that's the only way to have a properly exposed background and foreground.

Thanks for the help and info.!

you can do h-sync flash...as long as your subject is moving really fast.

DavidSR wrote in post #6288573
What I meant was to do 2 single exposures and merge them together in post processing. Basically one shot exposed for the background and the 2nd shot exposed for the subject. Seems like that's the only way to have a properly exposed background and foreground.

Thanks for the help and info.!

There are many methods of doing this. One is using flash (does not matter if you use 2nd curtain sync or not). Another is blending different exposures, another is HDR tone-mapping or you could use GND filters.

DavidSR wrote in post #6288573
What I meant was to do 2 single exposures and merge them together in post processing.

Absolutely that can be done, but there are others ways that may be easier.

But take a look at sapearl's post with the wedding picture in https://photography-on-the.net/forum/showthre​ad.php?t=561660 He estimates that it was a 20 second exposure to capture the background, with a flash used to clearly illuminate the bride and groom. This technique is called "dragging the shutter". It allows a long exposure for the background, either to capture ambient light or to capture motion, with a flash to "freeze" the motion of the subject.

krb wrote in post #6288643
He estimates that it was a 20 second exposure to capture the background, with a flash used to clearly illuminate the bride and groom. This technique is called "dragging the shutter". It allows a long exposure for the background, either to capture ambient light or to capture motion, with a flash to "freeze" the motion of the subject.

That was the same technique I was thinking of, I just thought that the slow shutter and flash to freeze the subject would blow out the subject because of the slow shutter. I'll have to give this a try next time I go there.

Thanks for all the help guys!

DavidSR wrote in post #6292368
That was the same technique I was thinking of, I just thought that the slow shutter and flash to freeze the subject would blow out the subject because of the slow shutter. I'll have to give this a try next time I go there.

Thanks for all the help guys!

You blow out the subject only when the [Flash exposure] + [Ambient exposure] = Overexposure

If the ambient level shutter+aperture exposure is -1EV, the subject would NOT be overexposed

Thanks! I'll have to give this a try sometime soon.