How to Use Photographic Flash

How To Use Photographic

Flash(and avoid “deer-in-headlights” look)

…and avoid the deer-in-the-headlights look

Original image copyright Getty Images

Review

You are probably sick of hearing

this, but…

Exposure

ApertureShutter Speed

ISOWhite Balance

ApertureAperture is the opening of the diaphragm inside a photographic lens. The size of this opening regulates the amount of light that passes through the lens onto the film or digital sensor inside the camera at the moment of the exposure.

ApertureAperture also controls the depth of field (DOF) - the distance between the nearest and farthest objects in a scene that appear sharp in an image.

Shutter SpeedShutter speed represents the time that the shutter remains open when taking a photograph.

Shutter SpeedShutter speed also allows us to freeze or blur moving objects.

ISOISO refers to photographic film's or digital sensor’s sensitivity to light. In modern digital cameras, ISO settings range from 50 to 6400.

ISOUnfortunately, in quite a few cases higher ISO means higher noise

White BalanceWhite balance refers to color temperature. Different light sources emit light at different temperatures. Light temperatures affect how colors are rendered in a photograph.

A Bit of History

Original Flash19th century flashes were made of magnesium powders (or other materials that created a short intense burst of light when ignited. Photographers would remove the lens cap (remember, this was before mechanical shutters were invented), hold the magnesium ribbon above the camera, light it and immediately cover the lens.

Modern FlashFlash as we know it today was invented in the 1930s by Harold Edgerton at the Massachusetts Institute of Technology.

http://www.tonyrogers.com/weapons/images/high_speed_photos/index.htm

Finally… Flash Photography

Flash Types

Pop-upHot Shoe

Strobes/MonolightsDedicated/Non-dedicated

Pop-upPop-up flash is the flash that’s built into your camera. It’s less powerful than an external flash, but the upside is that you always have it with you.

Pop-up flash can cause “red eyes”, a phenomenon caused by a reflection of the flash light from the subject’s retina.

It’s best to avoid using pop-up flash as main light source and only use it as fill flash

Hot ShoeHot shoe flashes are external flashes that can be mounted on your camera’s hot shoe. They also use the hot shoe to communicate with the camera.

Strobes and Monolights

Strobes and monolights are studio flashes. They provide much higher light output than hot shoe or pop-up flashes. The drawback is that studio flashes are heavy, fairly fragile and require external power.

Dedicated vs. Non-Dedicated

Dedicated flashes are designed to work with your specific camera brand and generally offer TTL (Through The Lens) mode. When most modern cameras measure light, they take into consideration the light reflected off the subject (as that light comes through camera’s lens). The camera tells its flash to shoot shoots a tiny burst of light right before the real flash and uses it to measure the light reflected off the subject. The real flash is determined according to this measurement.

Non-dedicated flashes will only work in manual mode and will not be able to communicate with your camera.

What Affects Exposure With Flash?

Working distanceAperture

Shutter speedSensitivity (ISO)Guide Number

Flash compensation

Working Distance

The distance between the camera and the subject is one of the most important factors on exposure in flash photography – you need to keep your subject within the flash’s range; if you are photographing a group of people, it is recommended to keep them in on same plane relative to the flash in order to guarantee consistent lighting.

Aperture

The aperture is the main factor that affects the exposure with flash photography since it determines that amount of light that enters the lens.

Shutter Speed

Shutter speed doesn’t influence the subject’s exposure when flash is used because the flash is ALWAYS faster than the fastest shutter speed. This is why the shutter speed only affects the background’s exposure and ambient light.

Guide NumberEvery flash has a guide number (GN), which measures the intensity of the flash. The guide number is stated in meters according to ISO 100. In order to double the GN you’ll need to increase the energy 4 fold.

FormulaTo determine the distance your subject should be from the camera with use the following equation:

GN/F-number (Guide number divided by the aperture)

For example GN 100 at aperture f/4 will permit a working distance of 100/4 or 20 meters.

ISO (Sensitivity)

Higher ISO = Higher flash efficiency!

Doubling the ISO will increase the guide number by 1.4 for ISO below 100 double the guide number for ISO greater then 100.

Flash CompensationMost modern cameras and flashes have an option for positive or negative flash compensation. This function gives us more control over the flash’s power output and ultimately over the scene’s exposure.

Flash Techniques

Fill FlashOff-Camera Flash

Direct FlashDiffusingBouncing

Slow Synchronization

Fill FlashFill flash is used in harsh lighting situations (when the sun is directly overhead and there is no shadow). Fill flash overpowers the sunlight and “fills in” shadows under the eyes and nose.

Off-Camera FlashUsing flash off camera allows for greater flexibility when it comes to positioning lighting relative to the subject and the camera. It also allows for more precise lighting (just throwing light on your subject without blowing out the background or lighting parts of your subject)

Photo courtesy of Travis Neely Photography (http://www.travisneelyphotography.com)

Direct FlashThe flash is directed straight forward towards the subject. It is characterized with harsh shadows and a little lighting from above.

Photo courtesy of Travis Neely Photography (http://www.travisneelyphotography.com)

DiffusingDirect flash usually creates very harsh shadows because of the small size of the light source. Using a diffuser makes flash’s light “bigger” and softer and to create gentler shadows and soft uniform lighting.

Diffusing - DIYFilm canister pop-up flash diffuser

Diffusing - DIYHot-shoe flash paper diffuser

BouncingWith a sheet of printer paper, scissors and a rubber band you can make a DIY diffuser in minutes.

If you don’t have a diffuser, you can bounce light off the ceiling or a wall. Bounced flash is always much softer then direct flash.

Slow Shutter SpeedSlow shutter speed (or shutter dragging) is used in low-light photography when you want to fire the flash and maintain the low shutter speed in order to expose the background. Longer exposures permit more ambient light to hit the sensor.

Recommended Reading

1. The Moment It Clicks: Photography secrets from one of the world's top shooters by Joe McNally

2. The Hot Shoe Diaries: Big Light from Small Flashes by Joe McNally 3. Strobist Photo Trade Secrets Volume 1: Expert Lighting Techniques by

Zeke Kamm4. Strobist Photo Trade Secrets, Volume 2: Portrait Lighting Techniques by

Zeke Kamm5. Speedliter's Handbook: Learning to Craft Light with Canon Speedlites by

Syl Arena6. On-Camera Flash Techniques for Digital Wedding and Portrait

Photography by Neil van Niekerk 7. Off-Camera Flash Techniques for Digital Photographers by Neil van

Niekerk

To Flash or Not To Flash…

Questions?

Contact

Dmitriy Babichenkowww.wideopenlens.com

dbabichenko@yahoo.com