If we have a
leaf shutter lens, will we still need a strobe that Does support
High Speed Sync like a
Profoto B1 or even with a normal Alien Bee can now shoot at 1/2000 second shutter speed because it is a
leaf shutter lens?
If we have a leaf shutter lens, will we still need a strobe that Does support High Speed Sync like a Profoto B1 ...
How HSS works with focal plane shutters is that the shutter curtains create a slit which travels across the image plane. The longer the shutter speed, the larger the slit. At a certain shutter speed, that slit becomes smaller than the image plane (sensor/film), and a flash burst will therefore only illuminate a part of it. HSS works by syncing timed pulses from the flash to the slit's travel across the sensor so that the entire thing can get some illumination from the flash.
A leaf shutter, however, works by having overlapping leaves iris in and out, so the sensor is uncovered from the center outwards. HSS pulsing, in this case, would do nothing but illuminate the frame from the center outwards, causing a gradient (kind of like vignetting). So, no, a leaf shutter does not work with HSS.
... or even with a normal Alien Bee can now shoot at 1/2000 second shutter speed because it is a leaf shutter lens?
You probably won't be able to reach 1/2000s (most medium format cameras with leaf shutter lenses max out around 1/800s-1/1000s), but they will sync more quickly than focal plane shutters. And if your shutter speed is within this limit, then you don't need HSS with a leaf shutter lens. The speed, however, is limited by the mechanical speed of the leaf shutter's opening and closing. And at certain speeds and aperture settings, the shutter leaves can still cover part of the sensor/film, and may cause your metering to become inaccurate. It all depends on the individual lens/camera combination.
The between-the-lens shutter with its X synchronization is preferred when using electronic flash. When you press the shutter release, the leaves of the shutter start their opening travel. It takes only a few milliseconds for the leaves to reach maximum opening. As this point is reached, a switch closes and the flash fires instantaneously. The blitz occurs, the shutter stays open for the pre-set time, and then the leaves begin a closing time that takes only a few milliseconds.
Most 35mm film cameras were fitted with focal plane shutters. This is an opaque curtain of cloth or metal leaves than race the full length of the film format. The shutter location, hovering just over the film at the back of the camera, is preferred when the camera will feature lens interchangeability. Otherwise, each lens barrel would require a shutter and its associated timing mechanism. In other words, the focal plane shutter keeps the cost down by simplifying the design of the interchangeable lenses.
The downside of the focal plane is this: the curtain travel time across the film plane is super lengthy. Since electronic flash blitzes in about 1/1000 of a second or shorter, the blitz can occur while the shutter is traveling. The result is, sadly, a partial image. The countermeasure is to use slow shutter speeds whereby the entire film area is uncovered. The trick is to trigger the flash at this perilous position. Note: the digital camera adopted this same shutter design.
The focal plane shutter has a slit that travels the entire length of the film or chip. The slit width is a variable, and the width is widened or shortened to set the exposure time. To get a high-speed sync, the flash must stay illuminated for the entire travel time. No small feat. The between- the- lens shutter is preferred, as it is best when it comes to capturing a blitz.