1st & 2nd curtain

jocose · Oct 20, 2005

I have a question about the above title. After playing with my camera a bit, I have discovered that one overexposes the scene more than the other.

Can someone explain:
1) what exactly is going on with the two
2) when to use each
3) historically, where the terms come from (sorry--I'm a bit of a history geek).

Thanks.

Rob · Oct 20, 2005

The below article explains a lot in detail, but here's quick guess for you:

First curtain is the shutter opening, second is it closing, giving you a window of time (usually about 1/125th) to fire the flash. It also gives you a literal window onto the film plane, hence curtain. Sometimes you want to take a picture in dark conditions and expose a fixed background naturally and a moving subject with the flash e.g. a portrait of someone in the dark.

http://photonotes.org/articles/eos-flash/index2.html

jocose · Oct 20, 2005

aaahhhh information overload

I'm reading the link you sent...good stuff, but lots and lots and lots and lots of it !!

hobbes28 · Oct 20, 2005

Summary is that 1st and 2nd shutter are flash synchs. It just means that you would rather the flash fire with the opening of the shutter or the closing. Usually, it fires in the middle so the first should operate as normal where the second should make the shutter stay open a bit longer and could potentially over expose your shot.

jocose · Oct 20, 2005

hobbes28 said:
Summary is that 1st and 2nd shutter are flash synchs. It just means that you would rather the flash fire with the opening of the shutter or the closing. Usually, it fires in the middle so the first should operate as normal where the second should make the shutter stay open a bit longer and could potentially over expose your shot.

so what are some practical examples of when you would use which?

(BTW, for the record, the manual that came with my camera sucks!!)

hobbes28 · Oct 20, 2005

Most manuals do...

Best reason to use syncs is for light streaks. You can take a picture of cars going down the road and have either the tail lights streak and the flash fire to show the car at the end or you can have it fire and show the car and have the lights trail through. I'll see if I can find some examples so I don't sound like your manual.

ksmattfish · Oct 20, 2005

Most cameras are 1st curtain. Some cameras/flashes have a 2nd curtain option. 1st curtain fires the flash just after the shutter opens. 2nd curtain fires the flash just before the shutter closes.

For very short exposures it usually doesn't matter which you use. With longer exposures it can alter how movement is captured. Imagine you are shooting at night, and you have a car coming at you. With a longer exposure and 1st curtain the car would be frozen by the flash, but the headlights would continue towards the photographer because of the longer exposure. It would look like beams shooting out of the headlights. With 2nd curtain the headlights would go towards the photographer, and then the car would be frozen by the flash. The light trails would be dragging behind the car, which is how people tend to think motion looks.

I don't know why your camera doesn't expose them the same. Somehow it must be metering them differently. Put the camera and the flash on the same manual exposure, and they should come out the same.

jocose · Oct 20, 2005

hobbes28 said:
I'll see if I can find some examples so I don't sound like your manual.

Thanks, Manual Hobbes.

OK, that didn't sound as dirty in my head as it does when I read it on the screet :lmao:

hobbes28 · Oct 20, 2005

jocose said:
Thanks, Manual Hobbes.

OK, that didn't sound as dirty in my head as it does when I read it on the screet :lmao:

Um..er...*runs away...* :lmao:

This is an example of rear sync by Nikon.

jocose · Oct 20, 2005

So you both use cars as your example, and it makes sense (Matt, I'm not sure I'm actually right about the different exposures...but to me one looked lighter than the other), but what else would you use it for? I mean, the idea couldn't have been created just to shoot car head and tail lights, could it?

I so need to buy me a tripod!

How do you get those kinds of shots...do you still use a lower shutterspeed, or does the 2nd curtain help make the effect?

ksmattfish · Oct 20, 2005

hobbes28 said:
Usually, it fires in the middle so the first should operate as normal where the second should make the shutter stay open a bit longer and could potentially over expose your shot.

If the shutter is staying open longer than it's set to, then the camera is malfunctioning. 1/15th of a second is 1/15th of a second whether you are using no flash, 1st curtain, or 2nd curtain flash.

Flash bulbs sort of fire in the middle of the exposure, and in some circumstances leaf shutter cameras/lenses the flash fire more in the middle, but with focal plane shutters (in almost all 35mm SLRs and DSLRs) it's definately either at the beginning or end of the exposure. Unless you are using something like the high speed sync feature like Canon flashes have, and then the flash is operating more like a flash bulb. In my example above, firing in the middle of the exposure would result in light trails extending both before the headlights, and trailing behind.

hobbes28 · Oct 20, 2005

ksmattfish said:
If the shutter is staying open longer than it's set to, then the camera is malfunctioning. 1/15th of a second is 1/15th of a second whether you are using no flash, 1st curtain, or 2nd curtain flash.

Flash bulbs sort of fire in the middle of the exposure, and in some circumstances leaf shutter cameras/lenses the flash fire more in the middle, but with focal plane shutters (in almost all 35mm SLRs and DSLRs) it's definately either at the beginning or end of the exposure. Unless you are using something like the high speed sync feature like Canon flashes have, and then the flash is operating more like a flash bulb. In my example above, firing in the middle of the exposure would result in light trails extending both before the headlights, and trailing behind.

Some of the advanced p&s's out there adjust shutter speed when you tell it to rear curtain sync and I think that Jocose is using the Canon S1 IS which, as far as I can remember, does the same thing. If it were an SLR, I would agree 150% with the camera being messed up. I used to have a Kodak DX6490 and it slowed my shutter down with rear curtain and I thought it was broken until I contacted them and they told me otherwise.

ksmattfish · Oct 20, 2005

jocose said:
I mean, the idea couldn't have been created just to shoot car head and tail lights, could it?

It's mostly about movement: either the subject or at the camera.

The flash is typically used to get some sharp details, and a longer shutter speed to show movement. Flash then finish the exposure shows the motion blur that occurs after the flash. 2nd curtain (exposure then flash) shows the motion blur before the flash. Movement is usually illustrated by showing motion blur dragging behind the subject; motion blur extending out in front of the subject may look odd to the viewer.

There is a technique of using a slow shutter combined with flash and intentional camera shake to get sort of an outline or halo around a subject, and blur the background. Depending on the situation the photog may prefer to move the camera then flash, or the other way around.

jocose · Oct 21, 2005

Thanks guys. Sorry to confuse about the overexposure thing...I may have been wrong. Hobbes, I actually have the S2, but I'm still impressed that you remembered!!

I have another question about motion, but I'm going to start a new thread as it's a little different...see in the new thread!