Pentacon Six Mount Cameras
by TRA

Flash photography with the Pentacon Six

Flash Synchronisation speeds with Focal Plane Shutters

Q: “Hi,
I have a bit of problem understanding how the flash system works on P6tl.  What I came across is that you set shutter speed higher than the flash sign, only half of frame will be exposed (I wish i have have read your instructions before shooting:)).  So if I understand right shutter speed has to be set at flash mode or slower right?”

You do understand right and have reached the right conclusion.  Let’s give a little more background.

Because the duration of light from an electronic flash gun is extremely short (typically a thousandth of a second or less), the time when it is discharged must be synchronised with the time when the camera shutter is fully open.

Cameras typically come with one of two types of shutter:

  • a leaf shutter
  • a focal plane shutter.
Each type of shutter has its advantages and disadvantages.

Leaf shutter

The “leaf shutter” is mounted within the lens.  It typically consists of three overlapping thin metal blades.  In German it is called “Zentralverschluß”.

Advantage Disadvantages
  • In quality lenses, it provides flash synchronisation at all speeds.
  • It typically has a maximum shutter speed limited to 1/500 sec, or even slower with some larger lenses.
  • As it has to be built into each lens, it adds to the cost, weight and complexity of each lens.
  • If it is to be coupled to film advance and other functions of the camera, complicated linkages may be required.
  • Because the maximum size of a leaf shutter is limited, this limits the possible maximum aperture of the lens, which is frequently smaller than the maximum aperture of lenses for cameras with focal plane shutters.

Focal Plane shutter

The “focal plane shutter” is mounted within the camera – just in front of the “focal plane”, which is where the film is located.
It consists of two shutter curtains which travel across the area to be exposed.  In German it is called “Schlitzverschluß”, which means “slit shutter”.
This is a good name, because the exposure is typically made by a slit of variable, pre-selected width traversing the film plane.

Advantages Disadvantage
  • It typically provides a high maximum exposure speed of 1/1000 sec, faster on some cameras (but rarely faster on Medium Format cameras, because of the large distance to be traversed by the shutter).
  • There is no need for a shutter to be built into the lenses, which makes them cheaper, lighter and simpler to make.
  • The maximum aperture of the lens is not limited by a built-in shutter, permitting much larger maximum apertures for some lenses
  • With no complex coupling between camera body and lens required to cock a shutter, it is possible to adapt longer lenses from older cameras with relative ease.  Even where hobbyists may not find this easy, other manufacturers can easily offer lenses in a range of mounts.
  • When used with electronic flash, it has a slow maximum flash sync speed, typically about 1/30 sec for Medium Format cameras.

The Pentacon Six has a focal plane shutter – just like the Exakta 66 (all versions of it), the Kiev 60, the Kiev 88, Norita, Pentax 67, etc.

With any camera with a focal plane shutter, the whole of the film is only fully exposed at the same time at the slower speeds.  The higher speeds are obtained by making the second shutter curtain begin to cross the frame before the first curtain has ended its travel.  This results in a portion of the frame being exposed progressively, as the gap between the two curtains crosses the frame.  The higher the shutter speed, the narrower the gap.

The highest speed at which the whole of the frame is exposed at one time is that indicated by the flash symbol on the shutter speed dial of all focal plane cameras.  In the case of the Pentacon Six, that speed is about 1/25 sec.  In practice, there are few occasions when one would want to use slower speeds than this with flash.  The exceptions could be night scenes where the camera was mounted on a tripod and a long exposure was used to capture the main part of the scene, with flash being added to capture a detail, perhaps a person who was posing within the picture area.

If you fire an electronic flash with the shutter set at higher speeds than the sync speed, when it fires, part of the film will be obscured by part of one or part of both of the shutter curtains, and that part of the frame will not be exposed by the light from the flash.  This is what you have discovered.  The higher the shutter speed, the narrower will be the open slit between the two curtains, and the narrower the area of film that will receive light from the flash.  This is not a fault in the Pentacon Six but a feature of all cameras that have a focal plane shutter, regardless of the make or format.

Most photographers find that most of the time a camera with a focal plane shutter is better suited to their photographic requirements than a camera with a leaf shutter in each of its lenses, and this resulted in the overwhelming market dominance worldwide of cameras with focal plane shutters from the early 1960s on.

If your particular type of photography calls for flash synchronisation at much higher shutter speeds, then you have two options:

  • either a camera with a focal plane shutter is probably not for you
  • or you could use a camera with a focal plane shutter, provided you use a flashgun with an FP bulb (but see the further considerations on the next page first!).

But for most photography, the Pentacon Six is a great camera that produces fantastic results, including with flash.

To go on to the next section, click below.
Next section (Flash sync at all speeds)

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© TRA April 2002  Latest revision: January 2014