But MF is used primarily for studio and landscapes, is it not? I would guess that fast moving subjects are more interesting to Canikon sports photographers?
I guess that a leaf shutter cannot be infinitely fast, just like the shutter of my 7D. What is the artifact caused by the leaf shutters "shutter time"? I would guess diffraction similar to a very small aperture?
It's not infinitely fast. One drawback of leaf shutter lenses is that they can only open and close at a certain speed. With a Hassy H that is 1/800th (depending on aperture), with a Phase One DF it is 1/800 with an internal electronic timing technology to allow an effective 1/1600th. With an RZ it is 1/400th etc etc.
The fastest that most Full Frame SLRs can transit the image is around 1/125th - 1/160th. To sync with a flash it's necessary that for some moment in time the entire frame be open (no shutter obscuring it) because the moment the flash fires any shutter in the way it shows up as a black section of the frame.
The "trick" that you are probably not thinking/realizing is that focal plane shutters can get to a faster "effective shutter speed" by using two shutters that form a slit. For instance a focal plane shutter can give you an effective 1/1000th of a second exposure by creating a slit that is about 1/6th the height of the frame. At no point in time is entire frame is being exposed. Actually the duration of shutter movement lasts around 1/125th - 1/160th of a second but any given section of the frame is only exposed for 1/1000th of a second so the ability to freeze action is equivalent to 1/1000th with the caveat of ultra fast moving objects (and then only for those traveling other-than-opposite-the-direction-of-the-shutter). The compromise is that since there is no point in time where the entire frame is being exposed you cannot fire a flash and have it expose the entire scene - only the area that the slit happens to be in when the flash fires.
So while focal plane shutter systems can go to a higher max speed they can only sync at a relatively slow speed. While leaf shutter lenses can sync at any speed they can go, they can only up to a relatively slow max speed. There is no free lunch. A select few systems like the Phase One DF and Leica S2 (assuming Leica makes good on releasing their here-to-fore unavailable LS lenses) have both a body shutter (allowing fast max speed) and a leaf shutter (allowing fast flash sync).
Also as to the comment about MFD only being for landscape and studio. That's simply factually incorrect, but markets vary widely across the world so I can see where you could get that impression. I manage the rentals out of our Miami office and we have four digital backs out on rental this week - all to fashion shooters and only one in a studio and that's a pretty typical week (during the Miami fashion season - winter). If you've never used a system with leaf shutter lenses in conjunction with strobes outdoors it's hard to understand how much more control they give you over your lighting.
Also, just in case you run across it and find it confusing - some systems like Canon and Nikon have dedicated flash systems (the SB### for nikon and the e.g. 580EX from Canon) which can "sync" at higher shutter speeds. It is a very useful tool, but it is not magic (no free lunches!) and has a major limitation. They achieve "sync" with very fast shutter speeds by changing from standard flash (where the flash fires once) to a pulsing flash method where the light pulses very very very fast (thousands of times per second) and therefore fires at least once for each section of the frame as the slit of the shutter travels across the frame. It's really cool actually, but by definition it greatly reduces the maximum power the flash can produce (since it is now trying to pulse rather than simply fire once).
So if you want to sync at f/5.6 at 1/1600th of a second at ISO50 (under exposing the sky/far-background by two stops on a sunny day) and then add flash to light up a full-length shot of a model standing 10 feet away you'll be able to do it with a single strobe head even if you put a modifier on it (soft-box/beauty dish etc) and a power pack using a MFD with a leaf shutter lens, but to do the same thing with a dSLR you'd need either many (many) SB800s in fast-sync-mode (pulsing light).
Doug Peterson (e-mail Me)
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