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omd:flash_superfp

super FP flash mode

introduction

  • SuperFP is a special flash mode which allows shutter speeds to be used faster than the x-sync capability of the camera-flash system
  • this is a mode invented by Olympus in the 1980's and 1st used on their Olympus OM system
  • other manufacturers have adopted this technology and call it High Speed Sync or HSS
  • FP stands for Focal Plane shutters
    • some cameras (mainly old film cameras) have a shutter inside the lens called a Leaf shutter, and these generally allow flash up to the fastest shutter speed (which is usually 1/500th sec on these cameras)

why can't we use normal mode flash at any shutter speed?

  • cameras such as most film SLRs and digital SLRs as well as mirrorless cameras have a mechanical shutter which sits in front of the film or sensor
  • at speeds at the “x-sync” or slower, this shutter is fully open when the flash fires and thus the who image is equally illuminated by the flash.
  • at speeds faster than the x-sync, the 2nd curtain of the mechanical shutter starts closing in front of the film or sensor while the flash fires, and thus a horizontal segment of the image will not be illuminated by any of the flash.
  • the faster the shutter speed, the greater the proportion of the image that will not be lit by the flash
  • cameras using an electronic global shutter mode without any mechanical shutter may be able to sync at any shutter speed, and this will be a highly desirable feature once the issues with such sensors are resolved, and this technology will potentially negate the need for a Super FP or HSS flash mode.

how does Super FP mode help solve this?

  • in Super FP mode, the flash fires a series of pulses throughout the exposure to give the effect of continuous lighting for the duration of the exposure
  • this then allows the whole image to be lit by the flash no matter how fast the shutter speed
  • HOWEVER, there is a MAJOR COMPROMISE - the effective flash output decreases substantially with every increase in shutter speed above the x-sync - this is why this mode cannot be used to overpower the full sun - your maximum flash_GN falls at much the same rate that the ambient light is decreased as a result of shortened exposure

why then would we use Super FP flash mode?

you need wide aperture for shallow DOF

  • the main reason is to allow a wider aperture and shallower depth of field (DOF) such as when using the flash as a fill-in light in outdoor portraiture in bright conditions
    • an alternative solution is to use a ND filter, but then this may adversely effect the ability of the AF system if the resulting light is too dim or the optical viewfinder view may be very dim, and of course you need to get the correct ND filter and put it on your lens

you need a fast shutter speed to stop subject blur

  • a 2nd scenario is when we are using fill-in flash and need a fast shutter speed to prevent subject movement, in this case, a ND filter will not help and Super FP mode may be the only other solution
  • slow shutter with fill-in flash is a major problem for outdoor portrait photographers using a prime telephoto lens without any image stabiliser capability as an x-sync of 1/200th sec may cause camera shake - luckily for Olympus camera users, we can use image stabiliser and resolve this problem very easily!

  • an undocumented hack will allow you to use faster shutter speeds than the x-sync without resorting to Super FP mode but you lose TTL auto exposure functionality:
    • attach a single pin hotshoe adapter (or a basic non-TTL capable flash) onto the camera hotshoe
    • attach a flash to this, and as the camera cannot detect a TTL-compliant flash, it will actually allow you to set a shutter speed faster than x-sync and still fire the flash
    • the trick here is to work out for each shutter speed, how much of your image will not get illuminated and ensure you compose so that your subject is not in that part of the image
    • take some test shots of a wall at different shutter speeds to see how this works
    • shutter speeds to 1/400th and even 1/500th sec are usable AND you get FULL flash output if need be.

how to set Super FP mode using an OM-D camera with an Olympus flash

  • The bundled flash that comes with the E-M5 or the built-in flashes cannot be used in SuperFP mode UNLESS RC mode is set to ON as this is the only setting within the camera where SuperFP can be turned on (see instructions as for the FL-600R)
  • External flashes with a mode button which allows SuperFP can also be used with RC = OFF.

using the Olympus FL-600R flash

  • set the camera to use flash as per usual (eg. flash mode in the camera settings to “Fill-in” to ensure it will fire)

using RC OFF

  • in this mode, you are not using remote control of flash and thus there are NO settings on the camera to set Super FP mode - this must be set on the flash unit itself:
    • attach flash to camera, turn camera on, then turn flash on
    • set the menu to RC = OFF in camera settings 2 menu to de-activate remote flash functionality
    • press the MODE button and the mode item will flash
    • while it is flashing, rotate the dial to choose either:
      • FP TTL - for TTL flash exposure, you need to also set the flash exposure compensation on the camera settings and on the flash (these will be additive so set one of them to zero to avoid confusion!)
      • FP M - for manual flash exposure, you need to also set the flash output level on the flash unit

a hack to allow manual radio wireless remote Super FP flash

  • if you want to trigger a remote Olympus Super FP mode compatible flash via radio wireless there is a workaround
  • start with the flash on the camera with RC = OFF on the camera
  • switch on flash and the camera
  • on the flash set mode to manual FP
  • the camera will now be set to FP mode
  • without turning the camera off, turn the flash off and remove it from the hotshoe
  • put a basic manual radio wireless remote trigger on the camera hotshoe and a receiver on the flash hotshoe
  • ensure the wireless trigger is set up correctly (ie. correct channels on each)
  • turn wireless trigger units on
  • turn the flash back on and it will be still in Manual FP mode so when it fires it keeps pulsing light at whatever output you had set
  • as long as the camera does not go to sleep or turn off you should be able to choose and shutter speed and gain FP mode flash albeit in manual flash output without any flash exposure compensation, etc.

using RC ON

  • in this mode, you are instructing the camera to use remote control of flash and to remotely set the settings of each flash and the controls on any attached flash will become deactivated and mode will display as RC (physically remote flashes will need to have their mode set to RC with the correct channel and group)
    • set the menu to RC = ON in camera settings 2 menu to activate remote flash functionality
    • while in Live View, press OK to display camera settings, if the remote flash settings are not displayed, press the INFO button to toggle to these
    • the top right item of the remote flash menu needs to be set to FP
    • then for each flash group you need to select either:
      • FP TTL - flash group will be set to automatic TTL exposure in Super FP mode, you need to also set the flash exposure compensation in this display
      • FP M - flash group will be set to manual exposure in Super FP mode, you need to also set the flash output level in this display
      • OFF - flash group will not fire
omd/flash_superfp.txt · Last modified: 2016/08/06 09:15 by gary1