I have just bought a Sekonic 758D flash meter. Today, everything is digital, Nikon flashes have the i-TTL technology, LCD screens are displaying histograms. Why would you need a flash meter with all these digital assistances?

Sekonic 758D


Let’s go back in time a little bit. I’m working exclusively with Nikon gear: DSLRs and flashes. I’m also using PocketWizard MiniTT1, FlexTT5 and an AC3 controller to quickly setup flashes settings from my DSLR.

Working without a flash meter

Until now, I had two options when I was using flashes for portraits photographies (flashes in i-TTL automatic mode, in manual mode, or in a mix of i-TTL and manual mode):

  • connecting the DSLR to a computer with an USB cable and using Lightroom to directly importing the photos from the DSLR (tethered mode)
  • being confident with the information available on the LCD screen of the camera: histogram, overexposed zones and the photos displayed on the LCD screen. This is the default setup when you are working outside or if you do not have the time to setup a laptop to work in tethered mode.

By using the tethered mode, you directly have the final rendering of your photo. Lightroom will directly process your file (NEF or JPEG) and display the final processed image. So, it is easy to modify flashes settings and directly see the modification made on the final image. It is a method based on experience and on iterative approximations.

On the other side, if you are not working in tethered mode, you will not have a lot of information on the LCD. The rendition of the photo you are seeing on this small screen is not as good as the rendition that you will have on your calibrated main computer screen. The histogram can help but it could easily be tricked if you are working with a white background or if you are taking a picture of a really dark scene.

Talking about white background. It is difficult to setup the flash power to have an homogenized white background. We could work with the over exposed function on the LCD screen but this is not perfect because this function is working on a picture processed by your camera and not the RAW file. By using this function, you will end up with a white background that will not be white everywhere or that will be too bright and light up your subject from the background, becoming a new source of light.

Regarding your subject, you need to have a lot of experience to understand how your camera will measure the light. There is as many photos configurations as ways your camera measures light. We are not Joe McNally and we do not have his many years of experiences (not yet at least).

So, if we are using an option or another, you will have to do a lot of iterations before having the photo you want to create.

Flash meter = manual

To test the flash meter, I have made two quick family photos. They are not complex photographies but they illustrate very will what are the advantages of using a flash meter.

The first example is a photo of my wife in front of a white background. I have used two flashes for this photography: one for the background and another inside a beauty dish to light her face.

I wanted a shallow depth of field. I have used a 85mm lens with an f/2.2 aperture. I have used a spot measure on the white background to have a f/2.2 measure by changing the flash power. As a spot measure is based on a 18% gray, you must add 2.5 stops to your flash power to have a 100% white. To be sure to have a perfect white, I have added 3 stops to my flash power to have a final measure of f/6.3.

For my wife face, I have measured the light under her chin and setup the flash power to have an exact measure of f/2.2.

I took 3 photos. The one displayed below is the one I prefer for her expression. But the most important thing to notice on this picture is that I did not had to change the exposure of this photo in Lightroom (ever for her face or the white background)! It is a huge time saver for your post production work and it is an insurance that you photo will always be well exposed.


The second photography was an even simpler photography of my son Thomas. Only one flash was used. Thomas was sitting in an highchair and I wanted to light his face and have a 1 stop difference with the wall behind him.

I have also used the 85mm lens but for this photography. I wanted a large depth of field. So I have used a f/5.6 aperture. I have first measured the exposure on the wall to have a f/5.6 exposure and changed the exposure time on my camera regarding the flash meter measure. The exposure time was 1/10th of a second. As I wanted a difference of 1 stop with the light on my son’s face, I had to take the photo with an exposure time of 1/20th of a second. I have setup the flash zoom to 200mm to have it concentrated on Thomas face and to not light the wall in the background. I finally had to setup the flash power by measuring the light under the chin of Thomas to have a f/5.6 measure. And that’s it! My camera was set with a lens aperture of f/5.6 and an exposure time of 1/20th of a second. These settings were quick to define and I took exactly the photo I wanted (at least regarding light).



Using a flash meter lets you take photos more quickly and more precisely regarding the light settings. You will have less post production work in Lightroom or Photoshop and you will take the exact photo that you had imagined.

In a further post I will explain you how to use a f/stop table with a flash meter and how to use the Sekonic 758D with a PocketWizard MiniTT1, FlexTT5 and AC3.

If you have any questions, fell free to ask them in the comments.

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