In the usual spirit of letting it all hang out - at least photographically - this is a follow up to my How not to shoot your kids post. I mentioned a lot of obstacles that I created for myself on that particular occasion and hope it at least caused a few of you to think about this honored endeavor of being elected to shoot "holiday" photos on demand. Really not my thing as I am sure it's not a lot of yours either.
Among my little photographic circle here that post and the included illustrative image on how that session played out generated quite a bit of conversation. As usual most of the topics were quite unexpected. The particular topic surprised me the most was some amount of discussion of my use of a single speedlight. I didn't really go into any degree of details in that post so I will in this follow up. I hope some of you find it useful.
The shot at the top is literally the very first test shot I made to test the flash exposure. I had already determined the ambient exposure I wanted based on a few factors. The first being 1/125 shutter speed so that I could hand hold the 105mm without motion blur in the background lights. I also imposed f2 as the aperture I was going to shoot at - not a great idea with two young subjects but I wanted to get as much light globe thingy going as possible just to see how it looked with my brand new Nikon 105DC. This only left ISO for controlling how the lights rendered. That turned out to be ISO 200 to keep the lights bright enough while attempting to negate any of the horrible CFL ambient that was bouncing around being thrown off by the interior light fixtures.
Here is the shot immediately preceding the one at the top to confirm ambient. You can still see a tiny bit of the CFL ambient on my test subject. That will be fine at that level really not enough for any real pollution. Any higher and it really could be a problem with strange color pollution in the shadows - no kidding. As an aside - you can make fantastic images with CFL's the problem comes in when you start mixing w/ daylight or tungsten. Horrible things will happen.
On to the one speedlight thing. I happen to shoot Nikon and happen to have a gaggle of SB-800's I bought years ago. If I were to buy more Nikon speedlights today I would go for the SB-700 with absolutely no reservations. Fantastic piece of gear at a decent price. Even though I happen to have plenty of lights that doesn't mean I have to use them all when one will do. In this circumstance space was at a premium and another stand or two would just be a pain in the ass. Additionally triggering a backlight with line of site IR is almost fool-proof.
Adding a key light in limited space may put the IR receiver behind you which is definitely NOT fool-proof and I really didn't want to fool with radio triggering. I am too cheap to buy $700 worth of new pocket wizard gear for on-camera control of power. I am also too lazy to run back and forth between flashes to control them manually without an assistant.
The general lighting pattern illustrated at the top of the post is insanely useful. Indoors, outdoors, one flash, two flashes, etc. Generally speaking it's two lights at about 180 degrees apart with the subject in between them. Those sources can be both hard, both soft, or a mix on either side. The number of looks you can get from this simple setup is infinite based on your shooting angle, exposure balance between the lights, relative color balance and if using strobes the amount of ambient fill you let in.
Maybe I will actually get the energy to do some serious images to demonstrate the possibilities I describe with an adult model soon (note to self - on to-do list). In this case I used one SB-800 to the rear and to the right of the subject. The key light was actually a 36" white reflector almost directly opposite that strobe in front and to the left. I used a reflector and reflector stand but it just as well could have been a white all, a window, another SB-800 strait up or modified with umbrella box/etc. If you only have one light this is a great way to go.
Typically If I choose to go this way with one light it will be hard with a reflector as shown or better yet a real window where the reflector is. In most circumstances this can fool even the most observant person into thinking it's the sun streaming in behind and a nice soft window lighting the subject. You can enhance that feel by bringing up the ambient exposure a bit and especially if you catch a bit of a real window in the background with daylight outside. In this case it throws off that feeling a bit due to the context of the out of focus lights and very low ambient I let in which screams night time.
In this particular circumstance of one hard light behind and a soft light in front that is not independently controllable you can still deal with ratios effectively if need be. For the most part I tend to let the hard source in the back blow out as long as it's not completely nutty and horrible. With a more cooperative subject you can make it look fantastic based on controlling where that hard light is striking skin/hair/etc but lets say you need a modicum of control over ratios like I wanted here.
Obviously the speed light is going to be way brighter in it's direct strike than after it travels further, bounces, becomes bigger, and then goes back to the subject. The first degree of control is relative distance. Specifically you can make them more the same by moving the speedlight farther away and the reflector closer to the subject. In this photo I opted for the speed light being as far away as possible in this room. It's about six feet behind the subject. Knowing that I had to light two subjects and have some degree of camera framing flexibility for the young and quite devilish subjects I could only get the reflector as close as three feet so that is what I did. Actually it's not too too over the top just using that limited degree relative distances.
If you need to further reduce the strength of the backlight relative to the reflected key light that's very possible even with not a whole lot of relative distance flexibility. All you have to do is aim the flash differently so that the fall-off is directly hitting your subject and the main pool of light is hitting your reflective surface. As a note the SB-800 even zoomed in to 105mm as I did has a very very slow fall off so radical reduction is difficult as the flash beam would be hitting the roof before you were able to make the reflector the same brightness or brighter than the beam hitting the subject. Some flashes have much steeper falloff but if they don't this is what a grid or snoot is for. A cheap speedlight grid will give you a much steeper falloff pattern and a pretty one as well. Armed with a speedlight grid you could easily get the reflector even with or brighter than the falloff hitting the subject if that is what you are going for.
As you can see the light is hitting the subject almost directly from the left side splitting the face in two. I don't really care for the first test shot which happened to be 1 stop over with my speedlight guess set at 1/16th power. With a tiny twist of the face the lighting would be text book perfect and does a pretty convincing job of looking a lot like a window to the left. In the above image I did enter a -1 in exposure prior to exporting this for the web otherwise it the left side of her face would be way too bright to see the subtle variation in tone created by the 36" cheapy-but-goody reflector. In real life I dialed the power of the speedlight down to 1/32 (equals one stop) and was ready to rock. As you can see from the subject's expression - she was not! Her sister was behind me doing some sort of gymnastic preparations for future olympic gold or something.
A couple of closing thoughts - first off is white balance and color temperatures. I typically render this kind of thing at about daylight even thought that is not technically accurate. If you were to use the camera's "flash" WB setting or a gray card to set WB the image would be crazy warm. That's fine if it's how you want your image to look but just consider for a moment that sometimes it might be better to go against common wisdom of accurate or warmer is better. If this were really the sun and a window you would be getting a much cooler temp from the main light than you would from the sun coming from behind. If you go with a color balance somewhere between 200 to 500 points cooler than neutral you will get a much more "window like" feel to the image which can be more appropriate or attractive with out screaming "too cool. too blue". This particular image is about as far cool as I go at 500 points below absolute neutral just for illustrative purposes.
I hope this gives you some food for thought - I swear I will get a bunch of more carefully constructed illustrations of this lighting pattern in various scenarios done early next year. One of my local photo-buddies as convinced me that it would be useful to a large number of people out there. Hopefully this longer explanation of my annual Christmas photo-nightmare gives you some things to play with over the holiday break.
Update: Here is a crappy diagram by request in case my description was hard to follow. Note - the words are more accurate in terms of scale and angle.