June 29, 2011 / FAQ
Technical Tuesday: Off-Camera Flash & High Speed Sync
It’s getting late on Tuesday and I really did not have much of an idea of what to write about today for a “Technical” blog post. I recently touched on post processing over on this post and while I feel I could easily keep writing about random Photoshop tips and tricks, an email this evening to Joanna talking about flash got me thinking in the right direction. Now, this is yet another topic (like Photoshop) that we could easily talk FOREVER about, so let’s focus on one teensy tiny little aspect: High Speed Sync.
Ok, now on to a real world application. Suppose I want to take a picture of Betty and Miles here on the corner. I want to show off the buildings behind them but of course still see my subjects. I also want to draw the attention to Betty & Miles and not the background so I want to choose a low aperture like f/2.8 to make the background out of focus and blurry. I set my aperture to f/2.8 on my EF 16-35mm f/2.8L lens, ISO as low as it will go to 100, and now the only thing I can control is thus my shutter speed. If I set my shutter speed low enough to see Betty & Miles (1/200 or so) then the background is too overexposed and I can’t see the buildings. I changed my shutter to a very fast setting of 1/1600 to cut the light down on the buildings and at f/2.8 here is the shot we get:
Ouch, a bit too dark, I can’t see my subjects! I could put my flash on top of my camera and fire away, but my subjects would look a bit “blasted” with the light coming straight on from the camera. If I really want to start adding some interest I need to move my flash off the camera in order to make the light more DIRECTIONAL so that I can create interesting shadows and add depth to the image. Now, using something like Pocket Wizards allows me to move the flash off the camera, which is a GOOD THING! The only limit is that the Pocket Wizards can only sync at shutter speeds of up to 1/160 of a second. So… if my shutter is *stuck* at 1/160, and my ISO is as low as it can go already at 100, the only other aspect of the Exposure Triangle I have control over is aperture. In order to balance the background and bring down the overall exposure from having a shutter speed of 1/160 I need to bring my Aperture to f/11. I change my power settings on my flash to become stronger to compensate (Aperture controls Flash exposure) and I get the following image:
Now, I could just end here as the photo isn’t bad technically (exposure-wise, ok I know the composition isn’t the best, this was done to show flash!). I’m happy with the photo, I can see my subjects and at the same time see the buildings in the background. Let’s try one more thing: High Speed Sync. What is High Speed Sync? This allows you two cheat the flash sync barrier and raise your shutter speed above 1/200 on a Canon camera. By turning this option on I can now bring my shutter speed to my original setting of 1/1600, which allows me to drop my aperture back down to f/2.8. Note, for this to work you need two Canon flashes for a Canon Transmitter or a camera that has a built-in transmitter (like the EOS 7D). Here I took a second Speedlite 580 EXII and that on top of my camera, set it to be the “Master” and then set my second flash that is still sitting on a flash stand to be the “Slave.” I turn both of the flashes to High Speed Sync mode, aim, and fire! Here is the final shot for this post:
You can see the difference between the two photos easily. This photo has a blurrier background because it was shot at f/2.8, but I can still see the city. Also, for those of you photo enthusiasts, you can see where the flash was coming from by looking at how the shadows fall on the subjects.
And that wraps up today’s quick Technical Tuesday post! Sorry if this was a bit boring for brides, we’ve got tons more of weddings and engagement sessions coming up! I had an absolute blast this past weekend with our wedding in Athens on Friday and then Midtown on Saturday! Head on over to our Facebook Fan Page for some previews.
Equipment Used in this Shoot (B&H Affiliate Links):
Zachary Long is an Atlanta wedding photographer and loves taking the flash off the camera to get dramatic portraits of his brides and grooms. Check availability on our portfolio website at http://www.FengLongPhoto/ or send us an email at FengLongPhoto@gmail.com.