You get caught off-guard with a photo assignment and you might not have time to set up additional lights or have the luxury of using a reflector. Maybe it’s an awards event in a large room and you don’t want the background to go completely dark. You see a celebrity, rock star, astronaut or maybe it’s the president of your company that you need to photograph (see image below), or maybe you just need to travel light, with a minimum of gear.
Shoe-mount flashes are very portable and you CAN use them to get a great image. The key to getting that image is controlling the balance of camera, flash, and ambient light.
The automatic advantage to shoe-mount flash units is that they use TTL metering, which stands for Through The Lens. This type of flash metering is much more accurate than the thyristor technology that precedes it, and it’s also easier to use correctly.
Camera manufacturers have their own versions of TTL flash and the alphabet soup of lettering can be a bit intimidating. Different types include i-TTL, P-TTL, E-TTL, etc. So what is the difference or similarity in each of these? Canon calls their flash technology E-TTL (introduced in 1995) or the newer E-TTL2 (since 2004). Firing a low power pre-flash immediately before the shutter opens, this type of Through The Lens metering is very accurate because the flash unit actually fires very quickly. This brief pre-flash determines the correct power output of the flash unit. The camera body and flash communicate together on the exposure by means of additional contact pins in the hotshoe and in the foot assembly of the flash unit.
Pentax’s P-TTL arrived in 2001 and it meters a low power flash with the lens wide open before opening the shutter. Nikon’s i-TTL has been available since 2003 and also uses a pre-flash to calculate the amount of light needed by the flash. Their TTL-BL is a separate mode for fill flash, with the idea of it giving you better balanced light, but for it to work accurately the subject needs to be darker than the background. So all of these systems are similar and no matter what brand of camera system you have, one of them will work great for you.
All of this solves the problem of getting the correct amount of light on the subject, which is weighted with the area of focus that you and your camera have selected. What about the surrounding elements in your artistic composition? You are seeing a potentially great image in the viewfinder, and whether you’re indoors or out, you want the flash to match the scene just enough to make it look right.
MATCHING THE LIGHT
Let’s take the example of photographing indoors. The best way to do this that I’ve found is to meter the ambient light in the room first. The camera can be in any exposure mode to take this reading. If for example, your exposure is 1/30 at f/5.6, ISO 800 – you would then switch the camera to Manual mode and make those your camera settings. Note that some cameras have a slow sync setting, or you could also use shutter priority to get this same balance.
You can leave the flash set on TTL mode and let it adjust its power output automatically. When you take the image you should have a remarkably balanced exposure. This can be further fine-tuned by adjusting the flash exposure compensation to add a little more, or a little less, fill light to the image. Flash exposure compensation can be added on the flash unit itself, or by adjusting the settings in the camera.
If you find that you need a little more depth of field to get your subjects in focus you can bump up the ISO to 1600 and lower the aperture setting to f/8. If you can use less depth of field, do the opposite by lowering the ISO to 400 and opening your aperture to f/4. There are always tradeoffs to be made, and you might not be able to handhold that particular lens at 1/30 second to get a steady image. Try using a monopod or tripod to help with that issue. For a faster shutter speed you might want to try 1/60 at f/5.6 with 1600 ISO. If you need to get your depth of field back to f/8 then you might need to be daring and go to 3200 ISO. Digital noise levels are improving all the time so don’t be afraid to try a higher ISO.
If you are photographing outdoors the opposite is true. Go to the lowest ISO to match your ambient light with your flash. There’s no way a flash can compete with the sun, so if you can select a lower ISO you will have a better chance of balancing ambient and flash at f/8 or f/11, rather than f/16 or f/22.
Some flash units come with diffusers and I’ve had good luck with those. These are usually plastic, and they snap on tightly in front of the flash. There are also many innovative aftermarket diffusers available. Some units are a card type that bounce the light and redirect it to a larger pattern. Some diffusers are of the softbox type with a diffusion panel that the light passes through.
Some diffusers take the plastic design to a much higher level (such as the Gary Fong brand). All of these diffusers are variations on taking a directional light, such as an on-camera flash unit, and modifying the light to lower the amount of shadow
that you would normally get from a harsh light source. My recommendation is that you try some of these for yourself and see what works best for you. Your flash, the environment you’re photographing in, and the type of photos that you take are
all factors that could determine which is the best one for you. If you have a favorite please let us know in the comments following this article.
Bounce flash is when you angle the flash head so that the light reflects off of the ceiling or a nearby wall to disperse the light. Due to light falloff less light will get to the subject, so having a low ceiling is helpful for this to work. Light falls off and can be accounted for using the Inverse Square Law – an object that is twice the distance from the flash head will receive one quarter the illumination – or two stops less light.
Off-camera TTL cords are another great option. I consider this to still be on-camera flash but the TTL cord allows you to be flexible with the direction of the light. Holding the camera in one hand, you can move the flash unit around with the other hand and try different variations of light on your subject. These cords are small, easy to carry with you, and they are relatively inexpensive. They’re a good item to keep in your camera bag.
Filters sometimes come with a shoe mounted flash, and they are also available from aftermarket sources. The most common filters are tungsten and fluorescent. These are a great, and often overlooked, option to match the color of light from your flash unit to the ambient light temperature of a room. Color temperature from a shoe mounted flash is similar to a daylight balance of approximately 5500 degrees Kelvin. Fluorescent lights are in the 4000K range and tungsten light is around 3200K, so using these filters will make quite a difference in the color of your final image. Give those filters a try the next time you’re in that situation.
Fill flash is a matter of finding the right amount of light to make the image appear to have been taken with natural light by using just enough flash to add catch-lights to the eyes, eliminate shadows, and give a more pleasing look overall to an image. You will be able to capture this balance using just your on-camera flash. It might sound difficult, but it doesn’t have to be.