john bishop images | photography | vancouver, bc

workshop session 6 – flash photography

  bounce flash, exposure, fill flash, flash, flash compensation, red-eye, slow sync, trailing curtain

the first part of the in-person version of session six of the Introduction to Digital Photography workshop was spent reviewing session five’s assignment – composition.

this is the last session that is based on camera technology – the flash.

flash photography

there are many ways to light a scene or subject for a photograph and they all have to do with changing the direction and the quality of the light falling on the subject; flash photography is one technique.

there are many types of flash units but we will be limiting our discussion here to either built-in flash units or external flash units, often mounted via a standardized “accessory mount” bracket or hot shoe. we won’t be talking about studio equipment where flashes may be large, standalone units, or studio strobes.

built-in flash units are powered by the camera’s battery and are controlled directly by logic in the camera. they can either be turned on manually (most digital SLRs) or automatically (most often on point-and shoot cameras through scene modes).

external flash units are usually restricted to digital SLRs and can be powered by the camera’s battery or externally. they are mounted using an on-camera hot-shoe adapter or can be mounted off-camera; these units are controlled indirectly by either wired or wireless (radio) connections.

most modern day flash units use a xenon filled gas tube to produce a burst of light that

1. has a colour temperature between 4500K and 5500K (daylight),
2. lasts about 1/1000 of a second, and
3. only reaches about 8 to 10 feet away.

modern flash units allow for the following modes for flash photography

• red-eye reduction
• bounce flash
• fill flash
• slow speed sync
• trailing curtain

red-eye reduction

the infamous “red-eye” is a result of light from the flash unit bouncing off the back of the retina in our eyes; the reflected colour may be different in animals. before the image is captured the flash is fired (often several times), causing the iris in our eyes to close down, greatly reducing this reflected light.

most modern day post-processing programs (Picasa, Lightroom, …) do have a red-eye correction tool that can help eliminate this strange artefact, but they do so by making assumptions about eye colour that may not give good results.  again, what can be done in-camera should be done in-camera!

this icon for red-eye reduction is located under a function or menu setting for both digital SLRs and point-and-shoot cameras.  it can usually be combined with some of the other flash modes.

bounce flash

bounce flash is more of a technique than a flash mode; you will not find an icon under your function or menu settings.

bounce flash involves changing the light’s direction and quality by bouncing it off another surface, typically a white card (usually plastic) held at an angle in front of the flash. external flash units often come equipped with such a card; they also usually have the ability to tilt the flash head back, allowing the flash’s light to bounce off a ceiling or wall.

be careful here and make sure that whatever surface you are bouncing the flash off has a neutral or gray-white tone. other tones will affect the colour temperature and may be problematic.

while not classically a bounce flash, i have had success with placing varying thicknesses of white tissue paper in front of the flash. this scatters the flash, softening the harsh highlights and shadows and can give pleasing results.

fill flash

fill flash is also a technique (ie. there is not icon to turn it on) that allows you to properly expose a subject that is in shadow when the background is bright.

the only difference between the left (no flash) and right (fill flash) images is the use of the camera’s built in flash! all the harsh shadows under the eyebrows, nose, cheeks, chin and hairline are gone and the face is evenly lit. the flash has smoothed out all the wide variations of light and dark across the subject, creating a more appealing, more natural look and feel.

using flash compensation with the fill flash technique increases or reduces the amount of light the flash emits, allowing us to fine tune the balance between a subject and its surrounds.

slow speed sync

at low light levels slow shutter speeds are needed to let in enough ambient light to properly expose darker backgrounds. slow speed sync is a form of flash that first exposes for ambient or background light and then fires a reduced flash to fill in the foreground.

on some digital SLRs, the icon for slow speed sync (sometimes shortened to slow sync) can also be combined with red-eye and trailing curtain modes. point-and-shoot cameras often refer to this mode as night scene or party scene.

trailing curtain

a variant of slow speed sync, the trailing curtain mode fires the flash just before the shutter closes rather than when the shutter first opens. if slow speed sync has been used the hand would have been frozen at the top of the arc and blurred through to the bottom – just the opposite of what we see here.

this mode helps convey a sense of motion and is often used in sports or action photography.

a simple camera flash can be used for much more than just making sure you subject is properly exposed. it can be used for fun and creative special effects.

assignment

the assignment for session six is to build a portfolio of ten images that represent the best of your efforts so far – use any ten photos you wish. they will be used in session seven – post-processing and publishing.