Forgotten in its old age

by Aditya

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I've always thought that shutters were composed of two vertical curtains that moved along the sensor in order to expose it (at least for most DSLRs). Recently I've bought a Pentax K1000 that surprisingly its curtains move horizontally instead in a vertical motion.

enter image description here

So, this raised a couple of questions:

  1. What's the difference between those systems?
  2. Is there any advantage in the vertical system over the horizontal system?
  3. How does this affect very high speed photography?
  4. Does a DSLR with a horizontal shutter exist?
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3 Answers 3

In terms of answers...

The difference is rather obvious and it's not all that dramatic, it's simply direction of travel. Vertical shutters do have an advantage, however, in that is because they have less distance to travel, a third less. That allows for faster flash sync speeds and faster shutter speeds.

At any rate, I think modern dSLR cameras are vertical. I'm not aware of one that is horizontal, but it may exist...

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2  
It's also a lot easier to gear the shutter-curtain reset to the film advance lever when cloth curtains travel horizontally; wind-on is noticeably smoother and faster. Not something you need to worry about with an electrically-driven return (either a motor drive with a film camera or a DSLR). And with cloth shutters, the camera can be thinner, squatter and have a higher viewfinder eyepoint if the rollers are on either side of the film frame rather than above and below. –  user2719 Mar 2 '12 at 16:38

The horizontal shutter was common in film cameras. The classic bodies had very simple mechanisms to roll the film onto the takeup reel, and to cock the shutter. Horizontal shutters came out naturally from that design.

Most classic film cameras can't do the very high shutter speeds that we are used to with DSLRs. And most can't have has high of a sync speed. My Nikon F can only sync at 1/60, because the shutter has a long way to go, and its all mechanical.

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I certainly think of my Maxxum 9 as a classic -- partly because it provides X-sync at 1/300<sup>th</sup> (as did its predecessor, the 9xi). Oh, and a top speed of 1/12000<sup>th</sup>. I don't know of any DSLR that can match that yet (kind of sad, considering the 9xi came out in 1992). –  Jerry Coffin Mar 2 '12 at 22:55
    
@Jerry — "most". :) –  mattdm Mar 3 '12 at 0:26
    
Having disassembled lots of SLRs in my youth, I can confirm this. Horizontal shutters were using cloth as a curtain, which got rolled up when cocking the entire shutter mechanism. Later SLRs then had the vertical shutters without curtain but with blades. These required more complicated mechanics. –  Thomas Tempelmann Apr 21 '13 at 10:08

There is a practical implication beyond faster X-sync speed.

Above its X-sync, a focal plane shutter is basically a "rolling" shutter -- i.e., one curtain opens, but the other curtain starts to close before the first has fully opened, so you end up with a "slit" moving across the film/sensor plane. As you go to higher and higher speeds, that slit gets narrower.

This can cause linear distortion with fast-moving objects. With a vertical shutter, an object that's moving horizontally will be in one position when the shutter is open at the bottom of the frame, and a different position when it's at the top of the frame. With horizontal curtains, the same thing can happen, but with objects moving vertically instead.

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Which, by the way, is why those early vintage racing car photos all have those "go fast" slanted elliptical wheels—it takes a long time for the focal plane shutter on a Crown Graphic or a Speed Graphic (a 4x5 "press camera") to travel top to bottom. (The image is recorded upside-down, so the bottom of the wheels shows where the car was when the shutter started, and the top of the wheel is recorded a little later. Really kewl effect, that is. You need to pan backwards at a very high shutter speed to duplicate it in-camera these days.) –  user2719 Mar 3 '12 at 4:03

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