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Tips and techniques

Use Flash to Light the Landscape

By May 18, 2016No Comments

Story and photos by John Gerlach

Devil’s Garden near Escalante © 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.

Devil's Postpile © John Gerlach

False Kiva in Canyonlands © John Gerlach

The flash exposure formula using guide numbers written three different ways:

  1. GN = FD x Aperture
  2. Aperture = GN/FD
  3. 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.

Devil's Postpile © John Gerlach

Orange Spring Mound in Yellowstone © John Gerlach

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
  • f/8
  • 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?

  1. Switching from ISO 100 to ISO 800 increases the GN by three stops
  2. The GN 60 meters is obtained by zooming the flash head manually to 200mm
  3. Shooting two Speedlites simultaneously produces one more stop of light
  4. 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.

Devil's Postpile © John Gerlach

Alien’s Throne of the Bisti Wilderness in New Mexico © John Gerlach

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.

  1. Use a more powerful flash
  2. Increase the ISO
  3. Reduce the flash to subject distance
  4. Open up the aperture
  5. Shoot with a tilt lens
  6. Focus stack to use a larger aperture
  7. Use a faster lens so you can focus stack with a bigger aperture
  8. No polarizer or any other light-absorbing filter
  9. No teleconverter or extension tube
  10. No flash diffuser
  11. Increase the FEC
  12. Point the flash accurately
  13. Increase the flash zoom focal length
  14. Use the flash manually
  15. Use the maximum power level in manual
  16. Use a flash extender
  17. Fire one flash more than once during a long exposure
  18. Use multiple flash
  19. Use multiple exposure
  20. 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