wildlightphoto Posted January 25, 2012 Share #41 Â Posted January 25, 2012 Advertisement (gone after registration) Unfortunately there is no useful way of stopping charge accumulation. Â That's what the central shutter is for. Link to post Share on other sites More sharing options...
Advertisement Posted January 25, 2012 Posted January 25, 2012 Hi wildlightphoto, Take a look here Leaf shutter, anyone?. I'm sure you'll find what you were looking for!
mjh Posted January 25, 2012 Share #42  Posted January 25, 2012 Of course. I was talking about electronic means of emulating a shutter here. The point was that while Leica couldn’t implement a full-fledged electronic shutter with this sensor, they apparently (that is if I’ve understood correctly what Stephan Schulz was hinting at) implemented half an electronic shutter – the shutter opens electronically and closes mechanically. Nifty! Link to post Share on other sites More sharing options...
wildlightphoto Posted January 25, 2012 Share #43 Â Posted January 25, 2012 Nifty! Â Very Link to post Share on other sites More sharing options...
giordano Posted January 26, 2012 Share #44  Posted January 26, 2012 Of course. I was talking about electronic means of emulating a shutter here. The point was that while Leica couldn’t implement a full-fledged electronic shutter with this sensor, they apparently (that is if I’ve understood correctly what Stephan Schulz was hinting at) implemented half an electronic shutter – the shutter opens electronically and closes mechanically. Nifty!  Yes - and this greatly simplifies the task of the central shutter. It needs to snap closed quickly and consistently, but it doesn't have to do the rapid close-open-close-open cycle of an ordinary leaf-shuttered SLR. Nor does it even need to open and close quickly (e.g. for a 4 ms exposure). In other words it should be a doddle to develop. So why on earth is it taking so long to release the CS lenses? Link to post Share on other sites More sharing options...
AlanG Posted January 26, 2012 Share #45 Â Posted January 26, 2012 Yes - and this greatly simplifies the task of the central shutter. It needs to snap closed quickly and consistently, but it doesn't have to do the rapid close-open-close-open cycle of an ordinary leaf-shuttered SLR. Nor does it even need to open and close quickly (e.g. for a 4 ms exposure). In other words it should be a doddle to develop. So why on earth is it taking so long to release the CS lenses? Â Â Leaf shutters that can work quickly have been around for a very long time. Electronic leaf shutters have been around since the 60s. In the scenario above the shutter will still have to quickly open fully after the mirror comes back down or the blackout time will be long. What could simplify the process and minimize vibration is if the focal plane shutter remained fully open whenever the leaf shutter is selected. Link to post Share on other sites More sharing options...
mjh Posted January 26, 2012 Share #46  Posted January 26, 2012 Yes - and this greatly simplifies the task of the central shutter. Perhaps more importantly it shaves off a couple of microseconds of the minimum exposure time. While the blades of the central shutter travel extremely fast – much faster than the curtains of a focal plane shutter –, their speed is still the limiting factor for the shutter speed.  In other words it should be a doddle to develop. So why on earth is it taking so long to release the CS lenses? Spoken like someone who has never actually tried to design a state-of-the-art central shutter from scratch … Link to post Share on other sites More sharing options...
giordano Posted January 27, 2012 Share #47  Posted January 27, 2012 Advertisement (gone after registration) Spoken like someone who has never actually tried to design a state-of-the-art central shutter from scratch …  ... but the point I was trying to make is that if the exposure is started electronically, the central shutter doesn't need to be state of the art. It has to close quickly and consistently, but other specifications can be relaxed a little. Link to post Share on other sites More sharing options...
mjh Posted January 27, 2012 Share #48  Posted January 27, 2012 ... but the point I was trying to make is that if the exposure is started electronically, the central shutter doesn't need to be state of the art. It has to close quickly and consistently, but other specifications can be relaxed a little. All that changes is that opening the shutter blades doesn’t need to be quite as fast; closing the blades still does. Since one movement is usually the mirror image of the other, I’m not sure it actually relaxes any design constraints. Also I wouldn’t expect Leica to say, oh, we’ve sped up the shutter by starting the exposure electronically so we can make do with a slower central shutter. Much rather they would use this speed-up to allow for even faster shutter speeds. Link to post Share on other sites More sharing options...
AlanG Posted January 27, 2012 Share #49 Â Posted January 27, 2012 I don't see why Leica would develop its own leaf shutter when it can just buy one. Link to post Share on other sites More sharing options...
mjh Posted January 27, 2012 Share #50  Posted January 27, 2012 I don't see why Leica would develop its own leaf shutter when it can just buy one. For Hasselblad, developing their own central shutter was one of the first projects they had started when developing the H system. At that point they hadn’t even decided on who would manufacture the H system lenses but they were sure they wanted their own shutter. And when you even design and manufacture your own lenses, as Leica does, surely you will want to develop your own central shutter to go with these lenses, no? This isn’t really comparable to a focal plane shutter. Link to post Share on other sites More sharing options...
AlanG Posted January 27, 2012 Share #51  Posted January 27, 2012 For Hasselblad, developing their own central shutter was one of the first projects they had started when developing the H system. At that point they hadn’t even decided on who would manufacture the H system lenses but they were sure they wanted their own shutter. And when you even design and manufacture your own lenses, as Leica does, surely you will want to develop your own central shutter to go with these lenses, no? This isn’t really comparable to a focal plane shutter.  You may well be right but Leica has used Copal FP shutters. Do you know if they are building their own leaf shutters? I guess I could see them not using an existing shutter if they were worried that the supplier might not be around in the future. Link to post Share on other sites More sharing options...
mjh Posted January 28, 2012 Share #52  Posted January 28, 2012 You may well be right but Leica has used Copal FP shutters. Yes, but central shutters and focal plane shutters aren’t really comparable in this respect. For one thing, a central shutter is an integral part of the lens so there are constraints entailed by the lens design. A focal plane shutter is a standardized component; basically you can take any of-the-shelf shutter that fits the specs (i.e. image size and maximum shutter speed / sync speed).  Do you know if they are building their own leaf shutters? They are. Link to post Share on other sites More sharing options...
giordano Posted January 28, 2012 Share #53  Posted January 28, 2012 Yes, but central shutters and focal plane shutters aren’t really comparable in this respect. For one thing, a central shutter is an integral part of the lens so there are constraints entailed by the lens design. A focal plane shutter is a standardized component; basically you can take any of-the-shelf shutter that fits the specs (i.e. image size and maximum shutter speed / sync speed).  It makes sense to look at the other side of the coin too. Standardised central shutters have been available for ages, and it's not so much that lenses impose constraints on the design of central shutters so much as that the standard shutter sizes impose constraints on lens design that had to be accepted in the past (e.g. the Hasselblad 250/5,6 and 500/8) but are no longer tolerable. Link to post Share on other sites More sharing options...
mjh Posted January 28, 2012 Share #54 Â Posted January 28, 2012 Which central shutter would you advise Leica to use then? Link to post Share on other sites More sharing options...
pico Posted January 28, 2012 Share #55 Â Posted January 28, 2012 For yet more information, recall that the Pentax 6x7cm film camera, which by design used a focal plane shutter, also had two lenses with leaf shutters. I am not perfectly confident in my recall, but while it could synch with electronic flash @ the leaf shutter max speed (1/500th?), the focal plane shutter had to be set at 1/8th of a second or slower. Â Regarding whether leaf shutter design or lens design drives lens development, please recall that the larger the leaf shutter, the slower it's minimum exposure time will be. It is difficult to move big leaves quickly. Fast lenses == big barrel, big shutters. Link to post Share on other sites More sharing options...
giordano Posted January 28, 2012 Share #56 Â Posted January 28, 2012 Which central shutter would you advise Leica to use then? Â I'm not in the armchair CEO business. Link to post Share on other sites More sharing options...
mjh Posted January 28, 2012 Share #57  Posted January 28, 2012 I'm not in the armchair CEO business. I thought you were applying … But in that case you will have to accept Leica’s decision to develop their own shutter. Link to post Share on other sites More sharing options...
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