In the first post of this series on Lighting for Portraits, I started with the words, knowledge, and insights of others in order to give us a basis for where to go and to show you how I started figuring out lighting. Now it’s my turn to tell you what I think about all of this lighting business.
First, let’s start with the basics and then we’ll build technically by adding modifiers, metering, and the technical aspects of lighting, the adding multiple lights, seeing the details, and – finally – where to go from here. The basics of lighting really begin with the main differences in the TYPE of lighting you’re wanting to use. You have the choice between shooting natural light (light that is reflected in our normal day-to-day lives from the sun), on-camera flash (exactly what it sounds like, a flash that is mounted on the hot-shoe of the camera that can be aimed directly at the subject or bounced off walls or other objects), and off-camera flash (where you’re using a remote to trigger a flash that is mounted on a stand somewhere else). For this series, we’re going to be focusing solely on off-camera flash since this is what I use almost exclusively and it’s the most fun!
I’m going to stick to how I quickly understood lighting control and how it applies to sports photography since that’s mostly what I like to do. It really boils down to understanding how the triangle (Aperture, Shutter speed, and ISO) affects your lights and your surrounding available light from the sun or constant lights. Here it is, are you ready?
Aperture affects your lights and your available light, Shutter speed only affects available light, and ISO affects the entire photo.
That’s it, that’s the basics behind the secret sauce that is lighting. Everything else is just positioning, attention to detail, and having a vision for what you’re trying to accomplish. But, let’s dive a little more into these key concepts to really determine why they do what they do.
First, let’s tackle ISO because it is the easiest to explain. ISO changes the light sensitivity of the sensor or film and it is an affect that is applied to the entire image. Whether the light comes from the sun, a movie light (constant), a flash (instantaneous), or whatever else, ISO doesn’t care. So, if you feel the entire image is too bright or too dark, then you can use ISO to adjust the overall image. I tend to leave my ISO at 100 if at all possible just because I want the best quality image I can create. If I’m inside and I want to balance the surrounding light with the strobe a little bit more, I might bump my ISO up to 200 or 400, but never any higher when I’m shooting with lights.
Next, let’s tackle Shutter Speed and its relationship to the available light and the strobes. First thing to remember, and this is VERY important when shooting with flash, your camera has a sync speed that you cannot exceed under any condition! This is specific to your camera manufacturer and can be found in your owner’s manual. But, all DSLR cameras have a sync speed that is higher than 1/200th of a second so as long as your shoot at 1/200th or slower, you’re covered. The reason behind this is that if you shoot any fast than this and you’ll start seeing the actual shutter because of the flash duration. This will appear as a black bar or a missing part of your image. No bueno. So, keep it below 1/200th and you’ll be fine. Now, onto the balancing act of shutter and aperture.
(Both photos taken at ISO 100, f/5. Photo on the left is at 1/100th and on the right, I dropped the exposure of the background and eliminated some of the light bleeding onto his face by bumping my shutter to 1/200th.)
Your shutter only affects the available light because the flash duration is too quick for your shutter to affect it.
If your flash duration is only 1/13,000th of a second, 1/200th won’t be fast enough to affect what the strobe is doing to your image. In fact, this is why I choose to use a quick flash! This is SUPER important if you’re wanting to stop action and here’s why: If you’ve ever shot action shots in daylight, you know that you need to be shooting at a high shutter speed – 1/1000th of a second – in order to stop the action and not get any blurring. Since we can’t do that if we’re shooting flash (because our sync speed is a meager 1/200th of a second), then how to do we stop the action?? We do it with our flash duration! The light freezes the action and the subject, so a quicker flash duration, the better the (for lack of a better term) stopping power.
(The action of Balazs riding here at +20mph is not because of the shutter speed, but because of the flash duration itself.)
So, now that I’ve covered that quick little sidebar on sports photography and freezing action, back to shutter speed and available light. Since you now understand why shutter speed only affects available light, how can you use this to create better images? A lot of my images have a lot of drama and a darker background to really make the subject pop in the image, this is done by upping or dropping the shutter speed. If I want to let more light from the available bleed into the image, I drag the shutter longer, if I want to allow the background to blur a little bit for a moving subject, I drag the shutter longer, or if I want to drop the exposure of the background and make the subject pop, I bump my shutter speed up and drop the background darker. Simple enough, and with a little bit of playing around it becomes super intuitive (light meters can be an AWESOME tool as well, but more on that later!).
Finally, we come to the crux of the lighting matter – Aperture. Aperture is where all of the honey is at for most aspects of photography. Depth of field, creating different types of sun flairs, for allowing more light in dark situations, or allowing less light if you’re wanting a slower shutter speed to drag and create motion. Aperture is GOLD in photography and that stretches into lighting as well. For lighting, aperture is where the balancing act is because:
Aperture affects both the power of your light AND the amount of available light in the image.
There is the statement, so let’s think this through as to why this happens. Forget lights for a moment, if I open or close my aperture the image gets lighter or darker respectively. That is how aperture affect available light and that rule doesn’t change when you’re shooting lighting and – if you’re preparing to shoot with lights – this shouldn’t be tricky at all or it’s going to make things pretty complicated. When we add lights, our flash becomes the driving force for what our aperture should be. Where you might be used to setting your aperture and dragging or speeding up the shutter to get the exposure you want, you now have the power of the light driving this aspect. The only way you can adjust how the light affects the image is by changing the power on the light, or opening and closing the aperture to determine how much of that light reaches your sensor.
(You can see that I have a very large depth of field here because I wanted to overpower all of the ambient light in the gym. I had to close my aperture to f/11 in order to achieve the darkness I wanted and balance the power of the lights with the ambient light via aperture setting.)
So, now you can see where that balancing act lies. If I have too much power coming from my light and I close my aperture up to counter it, then I’m letting in less and less available light. On the flip side, if I don’t have enough power from my lights and I open my aperture wide open, then I allow in tons of available light and I may not even be able to see the affects of my flash. This is the key to creating well exposed portraits with flash and it’s not something that can be just learned be reading this quick and dirty tutorial, it takes PRACTICE! Lots and lots and lots of practice!
You can do things to make it somewhat more intuitive or easier (i.e. light meter), but ultimately you still have to just have experience and understand how to read an image, see light, and read a histogram. A quick hint – use your histograms as a major guide when doing this. This is something that wasn’t explained to me when I first started and I had no idea what I was doing. If you’re taking portraits of people, pay attention to the red channel. This is where the skin tones are and if you see them spiking then you’re probably blowing out the subject in areas, and if you see them all in the darker spectrum of the histogram then you’re probably underexposing your subject (which may or may not be desirable depending on what you’re trying to accomplish).
I know I just dumped a lot of technical on there, but hopefully this helps give a basic understanding for how ISO, Shutter speed, and Aperture affect lighting and balance one-another to help you create the images you’re wanting with off-camera flash. Stay tuned to Facebook, Twitter, and Vimeo for a quick video coming soon on balancing available light and off-camera flash!