I have an Olympus FC-WR commander and an FL-700WR flash. The flash will show me the flash to subject distance when it's in the hot shoe, but not when I'm using wireless mode with the FC-WR.

Is there a way to get this information without swapping the flash in to the hot shoe? Or do I need to calculate it myself?


  • I don't know those models specifically, but I would bet that information is coming from the camera body, not the flash. Most speedlights don't have range-finding sensors attached, but the camera can tell you the distance it's focused at....
    – twalberg
    Feb 3 at 16:58

3 Answers 3


You need to calculate it yourself, or use the distance scale on your lens. (if it has one)

That flash (or any flash) does not show you the distance to the subject.

When used in the hot shoe, the flash takes ISO and aperture information from the camera to calculate the acceptable distance the flash can reach.

If set to TTL Mode, it will show you the “flash control range” which means the subject should not be closer, or farther, than what is displayed.

In Manual Mode, it will show you the “optimal shooting distance” which means the subject should be at the distance displayed in order to have correct exposure.

When removed from the hot shoe, or in bounce mode, the distance values disappear because there is no way to calculate the distance needed for proper exposure.

enter image description here

enter image description here

  • Upvoted. I'm pretty sure the flash calculates it and not the camera; but can only get the ISO/Ap when directly connected to the camera... it's not part of the preflash/power TTL wireless communication. Feb 4 at 16:09
  • You are correct, I edited my answer. Thanks. Feb 4 at 16:12

All camera flashes have a guide number. You can discover this value in the flash’s manual or you can test the flash and find the guide number for yourself.

Working in the English system (feet) the guide number for this flash is 138. Working in meters, the guide number is 42. These values are for a setting of 100 ISO.

Working in feet: Compose the shot and focus, the camera reveals the subject distance, say it is 12 feet. Divide the guide number 138 by 12 = 11 (rounded). Set to aperture to f/11.

Working in meters: Compose the shot and focus, the camera revels, say its 3.7 meters. Now divide 42 by 3.7 thus = 11 (rounded), Set the aperture to f/11.

For 200 ISO the guide numbs are 58 Metric / 193 English (1.4 is the multiplier).

Camera set to 200 ISO subject at 12 feet / 3.7 meters, set camera to f/16.


Tape measures come in many lengths from 1.5m to 8m to 100mm or more.

Cloth measuring tape


8m retractable tape measure


100m engineering tape measure

As an alternate to a tape measure, you can attach a length of string to your light stand just below where the light is mounted. You can then place color-coded marks or adhesive tape at several predetermined lengths. To adjust your light 12 feet from your subject, hold/clip/tape the 12 feet mark on your string at your subject and pull the light back until the string is fully stretched. One of the leading portrait studios in the U.S. at one time, Olan Mills, used the "string" technique in their portrait studios all over the country.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.