Story and photos by John Gerlach
Landscape photographers are exhilarated when a prominent portion of the landscape becomes illuminated with golden sunshine, especially when the sky directly behind it is a stormy dark gray. Unfortunately, these incredible displays of spectacular light are unpredictable and usually fleeting. Fifteen years ago I decided to use my Canon Speedlite to provide the blast of light I needed to light a rock ten meters across a raging river. My first flash attempts were futile since the Speedlite didn’t add any additional light to the rock. I pondered the situation for a while and finally realized I had “murdered” my Speedlite. Using ISO 100, a polarizer, stopping down the lens to f/22, and allowing the camera to set the zoom on the Speedlite’s flash head to 24mm to match the lens being used all conspired to make it impossible to light an object only ten yards away.
The Numbers Reveal the Problem
Using today’s current equipment, the Guide Number for the Canon 600EX-RT Speedlite is 60 meters when using ISO 100 with the flash head zoomed to 200mm. This Speedlite has a GN of 28 when the flash head is zoomed to 24mm. The polarizer adsorbs about two stops of light, cutting the guide number in half to GN 14.
The flash exposure formula using guide numbers written three different ways:
- GN = FD x Aperture
- Aperture = GN/FD
- FD = GN/Aperture
FD is the flash to subject distance in meters
The FD is ten meters. The GN is only 14 meters when the polarizer and the 24mm zoom setting on the flash are taken into account. Therefore, the aperture needed to achieve an optimum exposure is:
GN/FD = Aperture = 14/10 = f/1.4.
When the lens is stopped down to f/22, it is no surprise that the flash had no effect in lighting the rock across the stream. You can understand the small light of the top-of-the-line Canon 600EX-RT Speedlite is not nearly adequate for landscape photography! Or is it?
Change the shooting parameters to:
- ISO 800
- No polarizer
- Flash head zoomed manually to 200mm
- Two Canon 600EX-RT Speedlites being fired at once with wireless radio ST-E3-RT trigger
- A four shot in-camera multiple exposure is set
How has the lighting ability of the Speedlites improved?
- Switching from ISO 100 to ISO 800 increases the GN by three stops
- The GN 60 meters is obtained by zooming the flash head manually to 200mm
- Shooting two Speedlites simultaneously produces one more stop of light
- Shooting a four shot multiple exposure increases the GN by another two stops
The new effective GN is now six stops greater than GN 60 and becomes GN 480.
At what distance will this setup light an object? GN/aperture = FD
480/8 = 60 meters! Now the rock across the river is easy to light up with Speedlites.
How do you help the Flash light the Landscape?
Returning to that rock across the river years ago, I eventually realized I needed to empower the Speedlite by using different options. By removing the polarizing filter, setting ISO to 800 and f/8, and manually setting the zoom on the Speedlite to 105mm (my longest zoom setting at the time) allowed me to light the rock. Since then, I commonly use my Canon Speedlites to light large objects, multiple objects, and objects more than 50 yards away by using a combination of tactics. I have devised a list. There must be yet even more ways to expand the reach of the flash, so here is a challenge. Before reading this list, write down all of the ways you can think of to increase the lighting ability of a flash. You will score an “A” when you come up with twelve ways without first peeking at my list. If you are able to think of a new one, please pass it along to me. I am keen on increasing the length of this list while improving my ability to light objects with Canon Speedlites.
Twenty Ways to Empower lighting with Flash
I use flash to improve the color of objects in the landscape, to brighten a foreground, or as a fill light nearly every time I go out to photograph. In each case, I employ a combination of the twenty flash tactics listed below. Most commonly, I use ten or more of these tools simultaneously. Increasing the ISO, opening up the aperture, focus stacking, multiple flash and multiple exposure, using the maximum zoom setting on the flash, and using manual flash are regularly employed. Theoretically, the math states I can reach well over 100 yards, however seventy yards to light offshore tufa towers at Mono Lake is as far as I have taken it so far.
- Use a more powerful flash
- Increase the ISO
- Reduce the flash to subject distance
- Open up the aperture
- Shoot with a tilt lens
- Focus stack to use a larger aperture
- Use a faster lens so you can focus stack with a bigger aperture
- No polarizer or any other light-absorbing filter
- No teleconverter or extension tube
- No flash diffuser
- Increase the FEC
- Point the flash accurately
- Increase the flash zoom focal length
- Use the flash manually
- Use the maximum power level in manual
- Use a flash extender
- Fire one flash more than once during a long exposure
- Use multiple flash
- Use multiple exposure
- Combine flash with a flashlight
About John Gerlach
John Gerlach is an enthusiastic worldwide traveler who has been a professional outdoor photographer for four decades. He loves to explore every tool a camera offers as well as their accessories to make better images. John readily shares his techniques through workshops, seminars, his column in Nature Photographer, and instructional books including Digital Nature Photography – The Art and the Science, Digital Landscape Photography, Digital Wildlife Photography, and Close Up Photography in Nature. His latest book explaining advanced outdoor flash techniques including those suggested here will soon be published by Focal Press. Contact John at www.gerlachnaturephoto.com