Blacking out the background...?

I've noticed that on occasional shots, sometimes the flash will fill the area behind the subject, creating a fairly evenly lit image (indoors, bounce flash). But in other times, it creates almost a completely black background. However, I was wondering if anyone knows how the ISO, Aperature, and Shutter Speed play a part in altering this effect, along with actual settings on the 580EX. It would be nice to know how to control this occurance because it'd be nice to know how to do this. Any insight would be appreciated!

Yo Mario, Mario here.

I can't find the link, but I am sure others can find the Guide to Canon Flash use, that someone made a while back, and it is still one of the best online documents for learning all that stuff.

Best of luck,

I think the uide was originally posted by NCurtis and now is a stickey try starting here:
https://photography-on-the.net/forum/showthre​ad.php?t=138907

mjgravina wrote in post #2713629
Yo Mario, Mario here.

I can't find the link, but I am sure others can find the Guide to Canon Flash use, that someone made a while back, and it is still one of the best online documents for learning all that stuff.

Best of luck,

Great! Thank you so much! Haven't seen a lot of Mario's, even online. Hopefully someone will have the link.

Hey look! It's the Super Mario Brothers!


(Couldn't resist!)


As far as blacking out the background, if you're just using a speedlight on the camera itself (ie not a full fledge studio setup), just aim straight, and use a shutter speed and aperture high enough to block all the ambient light. Keep the subject as far from the background as possible so the flash's light falls off before it hits anything behind.

I've never tried to do this myself, so here's my less than two cent's worth. Take this with a grain of salt, and check for replies from those more experienced than I am.

If you want the dark background, you need to be in a mode that accomodates that with an external flash. You do NOT want to be in a mode that "properly" exposes the background and uses the external flash as fill flash (i.e., Av and, I think, Tv modes). I'm guessing that probably you'd want to use manual mode and set the aperture for the depth of field you want and the shutter speed fast enough to keep the background "underexposed" (i.e., darker).

As far as ISO goes, a general rule of thumb is to keep it as low as you can while still getting the aperture and shutter speed you want/need.

I always shoot manual so that is not a problem. I am just trying to understand the combination of settings that will achieve this.

Mario. wrote in post #2713689
I always shoot manual so that is not a problem. I am just trying to understand the combination of settings that will achieve this.

I edited my post so you may want to see if that gives you the results you desire. It should. If you need softer light for your subject, you'll be well served by investing in one of those softboxes that fits over your flash head. Lumiquest makes one I believe.

You would not believe in my photo assigments, how many grown ups (even politicians, names omitted) always end up asking me "hey, mario, where is Luigi?"...

Once I even brought an assistant to a Gala, and he was nicknamed Luigi the whole evening. I wonder why he won't work for me anymore. Not my fault, he did kind of look like the real thing.

mjgravina wrote in post #2713712
You would not believe in my photo assigments, how many grown ups (even politicians, names omitted) always end up asking me "hey, mario, where is Luigi?"...

Once I even brought an assistant to a Gala, and he was nicknamed Luigi the whole evening. I wonder why he won't work for me anymore. Not my fault, he did kind of look like the real thing.

Oh yea! I'm only 19, but it still happens all the time. My screenname and myspace addresses use the alias whereisluigi.

And somehow, the girlfriends always get called Peach. Funny how that works.

Mario. wrote in post #2713582
I've noticed that on occasional shots, sometimes the flash will fill the area behind the subject, creating a fairly evenly lit image (indoors, bounce flash). But in other times, it creates almost a completely black background. However, I was wondering if anyone knows how the ISO, Aperature, and Shutter Speed play a part in altering this effect, along with actual settings on the 580EX. It would be nice to know how to control this occurance because it'd be nice to know how to do this. Any insight would be appreciated!

From the Inverse Square Law, if the background is twice as far from the flash (pointed straight ahead) as the subject, the background will get 2 stops less lighting than the subject. For an average mid-gray subject and a mid-gray background, that should be enough to darken the bg enough to come out looking like black. Move the bg a little farther back if it's not dark enough for you. Or, move in closer to the subject if you can't move the background (and, of course, you'll need to adjust the exposure to properly expose the subject again).

NOTE: The above assumes that the main lighting is from the flash with very little or no ambient light reflecting off the background.

Go back and look at the shots you talked about earlier - I'll bet you that the shots where the background is dark have the subject closer to the camera than the background and vice versa.

Because of how light loses strength over distance, a distant background will appear darker than a close background.

Tom