I received the following question from our reader Rob.

Shooting indoors at night. I have a client that has reflexes so fast that her eyes are closed 90 % of the time. Using nikon d300 with nikon sb600. Use it on camera, off camera, TTL, rear sync, 250 to 20 and nothing worked. Turned model light off, turned it on. Threw something at the client to make them blink. Still nothing worked. Do you have any other suggestions? Regular light was enough to see but not enought to shoot with my 18-200 VR.

You are definitely not alone with this problem. There are many people who are sensitive to flash and blink every time they see it. Modern flash lighting technology uses so-called “pre-flash” to determine correct flash exposure. The main flash is emitted after the pre-flash with a delay in-between . If the delay is longer than the speed of human reflex, which is typically around 0.1 second, you have a good chance to capture closed eyes. The average length of a blink is 300-400 milliseconds. If the delay between pre-flash and main flash is anywhere between 0.1 to 0.5 second, the camera will likely capture eyes that are not fully open.

The delay between pre-flash and main flash is not the same for all cameras. Nikon D70, the first consumer class DSLR camera from Nikon, was notorious for this problem. The main reason that they cannot make the delay between pre-flash and main flash shorter is that it takes time for the camera to raise the mirror out-of-the-way. In Nikon CLS wireless flash system, the master flash also needs to communicate to remote flashes. That often makes the blinked eye problem worse by making the delay between first pre-flash pulse and the main flash longer.

Are there ways to avoid the problem?

The answer is yes. Depending on the options you have, it may not eliminate blinking eyes 100% but it can become manageable, unlike what Rob experienced.

  • Use manual flash. In manual flash mode, there is no pre-flash but only one single flash emission for exposure. The photo is already taken before the subject reacts to the flash. This approach is obviously limited to largely static scenes due to the need to dial in the flash output manually. For spontaneous shots in a dynamic setting it become impractical.
  • Use FV-Lock or Flash Value Lock function. With flash value lock button pressed, the camera performs the pre-flash sequences but does not fire the final flash to actually take the photo. The calculated flash output amount is used for the flash output when the shutter is pressed. With FV-lock, the photographer can give the subject enough time to re-open the eyes before taking the photo.
  • Use non-TTL flash mode. On Nikon Speedlight Flashes there is a so-called Auto Aperture (AA) mode. Contrary to many people’s believes, it still emits pre-flash but the delay between pre-flash and main flash is much shorter than the delay in TTL flash mode. Some camera/flash supports auto flash mode that turns off the flash when a certain reflected light is detected without the need to emit pre-flash.

There are also some other tips I have seen. For example, you can simply try to take more photos. As people’s eyes get used to the flash they may stop blinking. Another tip is to have people close their eyes and reopen on your count of 3. Press the shutter right after the 3. The reason this may work is that it keeps the eyes moisten so they are less likely to blink.

Posted in: Photography Lighting, Q & A on January 10th, 2012. Trackback URI
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