Tuesday, October 21, 2014

Photography Tip - Flash Sync and TTL FLash

While I have been boasting about the importance of shooting manual everything, whether it’s using flash or using a camera, I do understand there are occasions where being slow and deliberate can sometimes hinder a photographer’s ability to do their job. Case in point, event photography. This is the only occasion where I would not only recommend an automatic TTL flash (through the lens metering - the flash decides the power output based on your camera reading), but I would also recommend keeping the flash ON your camera (unless the venue/client allows for lightstands and off camera flash work). While you can get away with shooting in some auto modes like, shutter priority or aperture priority, I will explain below why I still shoot manually at events. 


From one of my event photography gigs. The flash was mounted on top of my camera at all times. 

Although I used off camera flash for this shot, you can bet I metered for the background first
Most cameras today use a traditional type focal-plane shutter, pioneered by Leitz for use in its Leica cameras which uses two shutter curtains that run either horizontally or vertically across the film or sensor plane. In order for a flash to “fill” or “expose” a sensor/film, the sensor needs to remain completely "open" before the shutter closes. When using a faster shutter speed both curtains are moving along the sensor simultaneously, which is why you may sometimes see a black bar running across your photo. For this reason most cameras can only properly sync with a flash at shutter speeds no faster than 1/200th or 1/250th of a second (I’ll talk about leaf shutters in another post). I will list what sync speeds work with cameras I have used/owned at the very bottom, but for now watch the YouTube video below which explains how the flash relates to the shutter curtains. 



Certain cameras will limit your shutter speed when it knows it has a flash or speedlight mounted on the hotshoe. Before I knew anything about flash, I would shoot in Aperture Priority Mode wide open every chance I could. I once mounted a flash to "try it out" during an afternoon shoot. I knew to properly expose a subject at f/2, I needed a shutter speed greater than 1/1000th. Well, I mounted the flash and was limited to the sync speed of 1/200th. You can guess that all my shots were overexposed because of this. Because of this experience I keep my camera in manual mode so I could adjust the aperture and ISO to compensate for the SS limits.  


This was a very difficult shot to take in that we were under a pier  with very little light. I metered for
what many photographers describe as God Rays. I then added an off camera flash to help expose for the couple.
*A special congratulations goes out to Steve and Lindsay for their recent marriage. 
Now that you know how to sync your camera with your flash, my photography tip for today is to meter for the background. Say you are taking a portrait of your subject at the beach right at sunset. The common thing to do is have your subject pose with the sun in the background - this causes a strong back-lighting situation, so adding a fill flash will be the wise thing to do. Before posing your subject, consider using your on-board camera to meter for the kind of sunset you want and follow these steps:

  1. Set your camera to shutter priority mode (you set the shutter speed manually and your camera selects the aperture & ISO for you) and select a SS that will sync with your camera & flash.   
  2. Fill the frame of your camera with just the horizon (no model). 
  3. Adjust the exposure up or down using exposure compensation
  4. Once you find a shot you like, review the image and take a reading of your Exposure Triangle: ISO, Aperture and SS.
  5. Set your camera to Manual Mode to mirror the settings in step #4. Once you set it you can simply forget it and worry about composition (the key reason why I shoot in manual)
  6. Pose your model and let the TTL Flash expose your subject. 
  7. Adjust the strength of your flash by adjusting Flash Compensation Up/Down. Some cameras have Flash Compensation built into the camera when using a proprietary unit. If you are like me and use third party flashes, you will have to adjust the flash compensation on the speedlight itself.
Unless you want a completely black background (what I wanted in this photo), then you will most definitely want to meter for the background first and then consider adding the light. 
You may be wondering why I meter for the background first and not the subject. Before I knew anything about flash and the exposure triangle, I would get frustrated with my built in flash especially when used at night. My eyes can see the colorful lights and ambiance, but the moment I fire the flash the background goes to black and my subjects look like they’ve been hit with a spotlight. By metering for the background first, you provide context to the picture which makes for a more compelling image. Next time you find yourself at an interesting location, remember to meter for the background first. I hope this helps and please let me know if you have any questions.

So say we all,

Dino



Below is some useful information about the FL-600r  (see our review HERE) and flash sync speeds with cameras I use frequently.



OMD E-M1: The Olympus OMD E-M1 is stated to sync at 1/320th. I can confirm that most of my flashes can in fact sync at this speed. When I use monolights, I tend to drop it down to 1/250th to make sure I don't get the black bands. 

OMD E-M5: While sharing the same sensor as the E-M1, the E-M5 has a flash sync of 1/250th. 


PEN E-P5: A smaller, EVF-less version of the E-M5 and has a flash sync speed of 1/320th. It was one of the selling points of the E-P5 and I can confirm it works .


Sony Alpha A7: Touted for having sync speed of 1/250th (a selling point over the A7r which can only do 1/160th of a second) does not sync at this shutter speed. All my flashes show a distinct black band on the upper half of the frame. You can get away with 1/200th with some cropping, but images are cleanest at 1/160th.