Underexposing backgounds..how?

[Hazey]

I have read a lot on strobist.com about metering for the ambient background and then underexposing by 2 stops to get that nice dark background and then use your strobe for lighting your subject.
My question is.....how do you do that? Is the most common way just to drop my shutter speed until the meter tells me I am two stops under? Or do some people do it another way? Is there another way or am I doing it correctly?
I am using manual mode.

[jcp2000]

from what i read its a faster shutter speed underexposes ambient lighting not slower. if you you use slower shutter speeds it allows more ambient light in, so if you want to underexpose it you need a fast shutter speed

[Andrushka]

start with a low ISO, smaller apertures (higher F/#'s) and faster shutter speeds or a mix of the three... the typical Strobist approach uses radio triggers for flashes and they can't sync above 1/200 or 1/250 typically... that leaves smaller apertures

[Hazey]

Argh! Sorry...I meant use FASTER shutter speeds...I just said it the wrong way around. Blonde moment. I know that the faster the SS the less light gets in.
So...SS IS the way to drop the ambient then. Thanks! Just needed to check.

[Andrushka]

Well, depending on your flash you will be limited to 1/250 at the fastest, unless you are using a high speed sync capable flash... In outdoor daylight, you will still need a pretty small aperture

Folks here can give you better/more specific advice if you describe your flash setup and the shooting conditions

[TMR Design]

Aperture controls flash exposure. Shutter speed controls ambient, or background exposure.
Slowing down the shutter speed increases the amount of time that the shutter is open and will therefore record more ambient light. Increasing the shutter speed decreases the amount of time the shutter is open and will record less ambient light.

I've attached 4 images. They were shot with on camera flash. Aperture remained the same in all 4 images. In the first image I used the shutter speed (1/60s) that the camera determined was correct based on it's metering and although there is nothing wrong with the image, for my taste the background is overexposed and there isn't enough contrast in the scene.

In the next 3 images that follow, I increased the shutter speed, allowing less ambient light to be recorded and got much more pleasing results. I much prefer the shots at 1/160s and 1/250 to the camera's default exposure or the second exposure with the shutter speed increased by 1/3 stop.

Of course it's totally subjective but you can see that keeping the aperture the same kept a constant exposure for the foreground tree and leaves, while the increase in shutter speed brought the background down in exposure, resulting in greater contrast between foreground and background.

[Hazey]

Great post Robert...I am a visual person and that was very helpful to me.:cool:
I just know that people always talk about underexposing the ambient when using flash...and I wasn't sure if there was another way of doing it besides increasing the SS.
Andrushka...mainly I am trying to do this in the broad daylight. I like that look where you can still see the background but the subject looks like they are under a spotlight almost. So it looks at though it was taken at dusk when it's during the day.
I think the aperture thing is part of the answer for me too as I was trying to use too wide an aperture for such strong light.
Am using a 430EX or SB-28 on a lightstand and firing with V2's.

[goatee]

You can also adjust the ISO to change the background exposure. Meter the scene, have the camera in full manual, and then adjust shutter speed / ISO to suit. Lowering the ISO allows you to minimise noise, and alleviates somewhat the maximum flash sync shutter speed.

[Dermit]

It's a fine line to walk sometimes. I shoot in Aperture Priority (Av) mode 90% of the time. But. Recently i've been shooting a lot more of these outdoor shots with underexposing the background like described here and I am finding Tv (Shutter Priority) is maybe a better choice at times. With the bright Arizona sun I struggle to get the largest aperture i can and keep the shutter to 1/200 or lower. By setting Tv to 1/200 and my ISO to 100 or even L (50) and then dialing in the exposure comp to -2 I know that my aperture is going to be as wide as it can go given underexposing the ambient light and now it's just a matter of turning up my flashes enough to expose the foreground subject properly (or move the flashes closer to the subject).

[umphotography]

Aperture controls flash exposure. Shutter speed controls ambient, or background exposure.
Slowing down the shutter speed increases the amount of time that the shutter is open and will therefore record more ambient light. Increasing the shutter speed decreases the amount of time the shutter is open and will record less ambient light.

I've attached 4 images. They were shot with on camera flash. Aperture remained the same in all 4 images. In the first image I used the shutter speed (1/60s) that the camera determined was correct based on it's metering and although there is nothing wrong with the image, for my taste the background is overexposed and there isn't enough contrast in the scene.

In the next 3 images that follow, I increased the shutter speed, allowing less ambient light to be recorded and got much more pleasing results. I much prefer the shots at 1/160s and 1/250 to the camera's default exposure or the second exposure with the shutter speed increased by 1/3 stop.

Of course it's totally subjective but you can see that keeping the aperture the same kept a constant exposure for the foreground tree and leaves, while the increase in shutter speed brought the background down in exposure, resulting in greater contrast between foreground and background.


TMR---YOU DA MAN:cool:.....thanks a ton,,im a visual guy myself. wheres curtis?? havnt seen him post for a while. you rwo guys really pass along alot a great info.

[TMR Design]

My pleasure guys. Many of use are visual and seeing things can make a lot more sense that talking and reading.

Once these concepts click and you take creative control of your camera you realize more and more why most good photographers, especially those using on camera flash, will shoot in Manual mode on their camera. When you stop letting the camera make decisions and use the camera's 'suggestion' as a starting point, you begin to see what can be done to make photographs that are better and more interesting.

[Dermit]

I agree, TMR's visual example absolutely rocks for this thread! It really shows how you, as the photographer, can dial in settings to control the look and feel of a shot a lot more than just shooting in the green box mode all the time and this is where the pros and amateurs go their separate ways.

It's noteworthy to bring up something that may or may not come in to play when excercising this underexposed background look. You have to be careful that you don't start to cast shadows created by the flash as this can move you back into the snapshot/amateur image look. Not always, but sometimes. If you look at your result and it looks like a flash photo (that typical flash look) then it might be due to this happening. In which case you may need to try and incorporate the same rules as indoor flash.... bouncing, or get the flash off camera, or use more than one flash... or maybe even let up a little on the underexposed background to let some of the ambient minimize or eliminate the shadow being cast. Keep in mind that the difference of this 'working' or not is often a very fine line and even moving the exposure ever so slightly can make a big difference.

It is often recognizing this 'sweet spot' and knowing how to get there in short order that makes you standout as a pro and therefore get's you more business.

[bobbyz]

Once these concepts click and you take creative control of your camera you realize more and more why most good photographers, especially those using on camera flash, will shoot in Manual mode on their camera. When you stop letting the camera make decisions and use the camera's 'suggestion' as a starting point, you begin to see what can be done to make photographs that are better and more interesting.


Very good point. I use to use Av mode earlier but now it is all manual with flash in manual or the eTTL mode. If I mess up, it is me not the stupid camera.

[umphotography]

Very good point. I use to use Av mode earlier but now it is all manual with flash in manual or the eTTL mode. If I mess up, it is me not the stupid camera.


x2 here. i only shoot flash in manual mode. i had a ton of problems shooting in av. manual is the only way to go especially if you have a L-358:p