Off shoe SB910. Will the background be dark?

<p>Hi. <br>

Yes a beginners question. <br>

Tomorrow i'm taking photos of a guy sitting in a chair with the background about 3-5 meters behind him. <br>

The SB910 will fire remotely into an umbrella just beside him to light him up. (And a reflector on the other side...doesn't really matter).<br>

But my question is.. will the background be dark? My guess is that it will not. <br>

Help.. I really hope so, because I need the background white. (The background is a wall almost only with huge windows and thin frames. But that's the way they insist I shoot it. </p>

<p>Thank you.</p>

<p>/S.</p>

<p> </p>

<p>At that distance it won't be white, at least not from the light from your flash. Use a tripod and see what the ambient light on the wall will be--that will give you a basis for choosing a shutter speed /f/stop combination that can give you the result you need. Or you might get lucky with the exposure on the wall from the window light. Good luck.</p>

<p>Good. Thank you very much Andrew.</p>

<p>The distance from the the main light to subject plays more of a role of making the background go dark or light than just the distance of the subject to background. You did not mention that distance. The further away the main light is from subject the less light fall off from subject to background and vise versa. The best scenario is to have the subject right on the background with minimum distance. The main light should be at least 5 to six feet away and have a fairly large umbrella (50inch) The farther away your light source the larger the umbrella or light shaper. Also when using a single light source don't go for ratio by having the umbrella off to one side and fill with reflector. That will make your background inconsistent leaving lighter on one side. go for the beauty lighting as they do for cover shots and use flat soft lighting by aiming the light source directly at subject from camera.</p>

<p>The shutter speed (up to the sync speed of the camera) will essentially control how bright/dark the background will be (assuming there is some light back there) w/o affecting the light falling on the guy (too much). That balances out w/ if the subject is moving and if there is blurring or ghosting (indicating too slow a shutter). So play w/ that parameter a bit (start w/ 1/30 or 1/60 or so and see what you get). Like Michael said, light falls off at a rate of the square of the distance so if your strobe is 5' from the guy and the guy is 5' from the wall, then the wall will get hit w/ 1/4 the power (2 stops less) than the guy. So, you do want to get him nearer the wall (watch for shadows though).</p>

<p>Bottom line, it's all one big balancing act between shutter speed, distance, strobe etc etc etc.</p>

<p>I was not even accounting for the ambient light as Howard has mentioned. This is all useful information to help us help you. You did say you were using a single light so I dont know how Howard assumes there is a background light. If Howard is talking about ambient light then what ever light is at 3 to 5 meters behind the subject is also hitting the subject as well so this is a totally different scenario. I would assume that there is no ambient light bright enough that would effect the exposure but that is totally dependent of how you the photographer set your camera settings. I would assume that you would shoot at 100 or 200 iso and set the maximum flash sync speed. </p>

<p>If you use the brolly as a shoot through, then it'll scatter light throughout the room. Whether the background will be light or not then depends on how reflective the rest of the room is, especially the ceiling, and how high the ceiling is.</p>

<p>Just let's clarify the situation. You say the wall behind the subject is mainly window? Are you saying there will be a window behind the sitter with daylight coming through it? If so, then all you need to do is set the aperture and shutter speed to overexpose the window light (slightly), and set the flash power to give a correct exposure of your subject's face for the aperture selected. Take a test shot without flash to see if you get a dark(ish) sillhouette of your sitter against a light background. If you do, then you're good to go with the flash. Setting the camera a fair distance away from the subject and zooming in will also reduce the apparent area of background in shot and give you more background options.</p>

<p>PS. I wouldn't put the reflector directly opposite the flash. This can give a dark underlit band down the centre of the face; looking like someone's drawn a line down the nose. Place the reflector more frontal and at an angle between the flash and the sitter to throw light onto the unlit side of the face. This may need a bit of playing with to get right, but is much better than just sticking the reflector 180 degrees opposite your key light.</p>

<p>Edit: Doing a bit of maths shows that there's no way one little SB-910 can get a sensible amount of light on a wall 5 metres away. That speedlight has a true GN of around 28 (metres/100 ISO), so you'd need to work at about f/2.8 at 100 ISO with the flash in an umbrella to get enough exposure on the wall. Of course that would mean that the sitter would also need to be 5 metres or so away from the light, and it ain't going to be a soft source anymore at that distance. Basically, if you haven't got the aid of daylight coming through a window, then you need a second source of light for the background.</p>

<p>I was not even accounting for the ambient light as Howard has mentioned. This is all useful information to help us help you. You did say you were using a single light so I dont know how Howard assumes there is a background light. If Howard is talking about ambient light then what ever light is at 3 to 5 meters behind the subject is also hitting the subject as well so this is a totally different scenario. I would assume that there is no ambient light bright enough that would effect the exposure but that is totally dependent of how you the photographer set your camera settings. I would assume that you would shoot at 100 or 200 iso and set the maximum flash sync speed. </p>

<p>I was not even accounting for the ambient light as Howard has mentioned. This is all useful information to help us help you. You did say you were using a single light so I dont know how Howard assumes there is a background light. If Howard is talking about ambient light then what ever light is at 3 to 5 meters behind the subject is also hitting the subject as well so this is a totally different scenario. I would assume that there is no ambient light bright enough that would effect the exposure but that is totally dependent of how you the photographer set your camera settings. I would assume that you would shoot at 100 or 200 iso and set the maximum flash sync speed. </p>

<p>honestly, when I read 'windows', my brain went to 'oh, this must be a daylight shoot'. My bad if that is not the case.</p>

<p>This is the danger of buying a strobe one day, trying to learn to use it the next and doing a shoot the next.</p>

Yes the exact background condition is unclear to make an educated guess. Still not enough info is provided. Is the

window the background or the wall? Is there light coming through the window and how much?

<p>Oh yes I forgot to say that it will be in the middle of the day with a lot of daylight coming through the windows. (It's a room made of glass on top of a very tall building, and a lot of light from the ceiling (The ceiling is not made of glass though).<br>

Thank you for all the interesting answers. I will have to make many test shots. <br>

/Sarah</p>

<p>The only way to make the outside go white is by overexposing the ambient light via your shutter speed. Your problem is there is the same ambient light flooding your shooting area. The best you can do is balance the outside light. The other detail you did not say is what the direct view is out the window is via the camera angle. Open bright sky will be lighter than buildings in the background. What I don't understand is why do you have to make the background white? If that is the case common sense says to use a white seamless background. Maybe you meant you just don't want a dark looking background.</p>