Understanding Fill Flash

One of the most confusing aspects of photography for the beginner is how to effectively use flash. Everyone who has ever used a point and shoot camera knows that flash can either be a friend or an enemy with more often then not it is not a friend for it will "blow out" their subjects since they have little to no control over their output.

When we move up to a digital SLR many will shy away from using flash for they base their opinions on past experiences but little do they know that just like having the ability to set the camera to their desired settings, we can do the same with our flash unit, especially those who use a hot shoe or external flash unit.

In order to get the most out of our images we must learn to embrace it, harness it and greet it with open arms. Be willing to experiment, accept our failures and bask in our successes and one of the easiest ways to get your feet wet is to use your flash unit as "fill flash".

By default, flash units all pretty much these days use a technology called TTL or E-TTL. Without getting into the science behind the magic, let's just say the flash manufactures have taken out most of the guesswork for us. It's now up to us to take that power and use it and fill flash is a great introduction to the science.

In a nutshell, fill flash is a term where we cut the power of the flash and use it just as the term says, where we "fill in" shadows with our flashes. We won't overexpose our subjects, we won't blow our highlights, but we will gently add light to where the natural or ambient light fails to reach.

By default, flash units will only allow you to use up to 1/250th a second shutter speed and the flash actually becomes your main source of light. If you ever have taken a photo with a point and shoot camera then you will see lots of over exposed images especially up close images of people for the flash will simply overpower the exposure.

So to get set up to use fill flash you simply set your camera’s flash (if you have a pop-up flash) or if you have a hot-shoe external flash unit by putting it in High Speed Sync mode. The universal symbol is a flash icon with the letter “H” next it as illustrated below. Now simply underexpose your flash setting to -1, which is called "Flash Compensation". Just like you can use exposure compensation on your camera to control the exposure you also can use flash compensation to cut the power of the amount of light the flash will fire so that it now simply becomes fill and not your main source of light.



Selecting “High Speed Sync” on your flash allows you to use a shutter speed now higher then 1/250th a second so you can effectively use your flash unit as Fill Flash.

You will also want to make sure you keep your flash in TTL or E-TTL mode so the camera will correctly balance the light when using your flash. The other big benefit using fill-flash is not only exposing your subjects more evenly, especially in open or full shade but you also get a nice benefit with catchlights in the eyes.

A catchlight is simply the highlight of a light source reflected off the surface of the eye. This highlight adds depth and dimension to the eye, and gives the eyes life. Without them, the subject will not look as vibrant or energetic and this is especially important with subjects that have dark eye colors like brown or deep blue. Take a look at the examples below of the difference fill flash can make and notice that my camera settings did not change as well as my background or other areas of the images exposure:



Here is the first shot of Lindsay where I had the flash unit off. Even in the full Florida sun, notice how the details, especially in her face and eyes, fall dark, even under the full blazing Florida sun.
ISO 100, Manual: 1/800 sec. at f/4.



I quickly turned on my flash unit and with the same exact camera settings and having my flash set to ETTL, -1 Flash Compensation and using High-speed Sync, notice now how much brighter her face is and I brought back al the lost details in the shadows as the fill flash "filled" them in.
ISO 100, Manual: 1/800 sec. at f/4.

So the question is “when should you use your flash to be used as fill-flash?”. The answer is all the time! Shade, open shade, indoors and you may be surprised to learn even in full sun. I have found that using flash in full, blazing sun does several things that will greatly enhance your images. I even use fill-flash when the sun is directly behind my subjects for if I didn’t, they would become silhouettes so with fill-flash, my background is exposed correctly and the light from my flash “fills in” my subject so the entire image is exposed correctly, both foreground and background.

First, you will fill in shadows that are very common with sunlight since depending on the direction of the sun you can get harsh shadows from the nose, around the eyes and if for example the subject is wearing a hat. By using fill flash you can effectively fill in those shadows for a more pleasing result.

Secondly, the model will see the flash fire and that will give them an indication that your have taken a photo and you will then notice that if they are somewhat experienced give you a totally different pose. This saves you from becoming a director and letting them know to do something else after each and every frame you take. Be sure to check your camera or flash manual on how set your flash to high speed sync so you can effectively open doors to new opportunities and creative avenues.