AlanG Posted January 18, 2012 Share #21 Posted January 18, 2012 Advertisement (gone after registration) 4. camera starts exposure The above probably means that the camera starts exposure via the leaf shutter as there is no other way to sequence this and they don't need to state the obvious. It's not as if the S2 is the first SLR with leaf and FP shutters. You would think that with a leaf shutter lens mounted, the ideal method would be to keep the focal plane shutter open to avoid additional vibration and wear. But maybe this causes a significant power drain. Link to post Share on other sites More sharing options...
Advertisement Posted January 18, 2012 Posted January 18, 2012 Hi AlanG, Take a look here Leaf shutter, anyone?. I'm sure you'll find what you were looking for!
mjh Posted January 18, 2012 Share #22 Posted January 18, 2012 4. camera starts exposure The above probably means that the camera starts exposure via the leaf shutter as there is no other way to sequence this and they don't need to state the obvious. I would have thought that “camera starts exposure” was stating the obvious … Anyway, there is a step “7. central shutter opens” and each opening and closing of the focal plane shutter is mentioned explicitly as well, so why not this step? Link to post Share on other sites More sharing options...
AlanG Posted January 18, 2012 Share #23 Posted January 18, 2012 I would have thought that “camera starts exposure” was stating the obvious … Anyway, there is a step “7. central shutter opens” and each opening and closing of the focal plane shutter is mentioned explicitly as well, so why not this step? I guess they missed it. Yeah, if they bothered to write anything they should have listed all of the detail for the shutter, aperture, and mirror actions in sequence. But it doesn't really matter much as there are only a few possible variations and they are not significant. I don't know if you are familiar with the Rollei 6000 series cameras but they had a stroboscopic mode that left the mirror up and could fire the shutter (leaf) 10 times a second. They also had a multiple exposure control that separated the mirror, shutter, and film advance sequences. It seems to me if you add an FP shutter to this you'd want the possibility of independent control over it when a leaf shutter is in use. (Keep it open.) I don't know if the S2 will have a mirror lock that also opens the rear shutter when using the leaf shutter in order to minimize vibration since there is no need to use both shutters. It would also be nice to know if leaf shutter efficiency is compensated for electronically to vary the open duration depending on the size of the aperture and the selected speed. Link to post Share on other sites More sharing options...
giordano Posted January 18, 2012 Share #24 Posted January 18, 2012 It would also be nice to know if leaf shutter efficiency is compensated for electronically to vary the open duration depending on the size of the aperture and the selected speed. Some of the descriptions of the CS shutters have left me with the impression this would be the case. I can also imagine that problems with this could contribute to the delays in releasing the CS lenses. Link to post Share on other sites More sharing options...
lars_bergquist Posted January 21, 2012 Author Share #25 Posted January 21, 2012 According to Leica S2 product manager Stephan Schulz, this is the CS firing sequence: shutter release is pressed mirror goes up focal plane shutter opens camera starts exposure central shutter closes focal plane shutter closes central shutter opens mirror returns Hope this helps. When I used the CS lenses, there was a very slight delay which didn't prove to be a problem when shooting. David Doug, just two posts above mine, Dave Farkas wrote this. Note that his point four is "camera starts exposure", not "central shutter opens". If that was what he meant, he should have said so, and there would have been no misunderstanding. And I think now that this was what he meant. My fault then – for assuming that other people try to express themselves as precisely as I try to do. That may well have to do with the fact that English is not my first language. The old man, removing his ear wax Link to post Share on other sites More sharing options...
wildlightphoto Posted January 21, 2012 Share #26 Posted January 21, 2012 It seems what's unclear is how the camera starts the exposure. Is it via the focal plane shutter? The central shutter? Or electronically? Link to post Share on other sites More sharing options...
mjh Posted January 21, 2012 Share #27 Posted January 21, 2012 Advertisement (gone after registration) I don’t see how an electronic shutter could be implemented with a full-frame transfer CCD. Link to post Share on other sites More sharing options...
wildlightphoto Posted January 21, 2012 Share #28 Posted January 21, 2012 I don’t see how an electronic shutter could be implemented with a full-frame transfer CCD. If an electronic shutter can be ruled out we're left with either focal plane or central. As I see it using the focal plane shutter to start the exposure would diminish the purpose of the central shutter. Link to post Share on other sites More sharing options...
mjh Posted January 21, 2012 Share #29 Posted January 21, 2012 If an electronic shutter can be ruled out we're left with either focal plane or central. Yep. And the next question is: Would it be possible to start the exposure with the first curtain of the focal plane shutter (and the central shutter already fully open) without creating an uneven exposure, especially at high shutter speeds? As far as I know, if you start the exposure with the first curtain opening you have to stop it with the second curtain closing. Terminating the exposure with the central shutter won’t do, unless it was also used for starting the exposure. So either “exposure starts” means “central shutter opens” or there is something else going on that I don’t understand. Link to post Share on other sites More sharing options...
AlanG Posted January 21, 2012 Share #30 Posted January 21, 2012 Yep. And the next question is: Would it be possible to start the exposure with the first curtain of the focal plane shutter (and the central shutter already fully open) without creating an uneven exposure Maybe they'll use electronic image processing to compensate for the unevenness. Just try shooting at 1/500th of a second with this method and you'll see it can't work. It is obvious how one would use the leaf shutter...FP shutter opens while the leaf shutter is closed, then the leaf shutter makes the exposure and closes, then the FP shutter closes and the leaf shutter opens fully. The mirror goes up sometime before the exposure and returns sometime after the exposure. So why all of these posts? Link to post Share on other sites More sharing options...
mjh Posted January 21, 2012 Share #31 Posted January 21, 2012 So why all of these posts? Because the sequence posted by Dave is at odds with what would appear to be the most logical sequence. Link to post Share on other sites More sharing options...
AlanG Posted January 21, 2012 Share #32 Posted January 21, 2012 Because the sequence posted by Dave is at odds with what would appear to be the most logical sequence. Haven't we concluded that this is a simple mistake of omission since the FP and leaf shutters must work in a certain sequence? We know that at step 4 the leaf shutter has to open for it to work. Link to post Share on other sites More sharing options...
mjh Posted January 21, 2012 Share #33 Posted January 21, 2012 Haven't we concluded that this is a simple mistake of omission since the FP and leaf shutters must work in a certain sequence? Maybe Dave can shed some light on this but I’m not jumping to conclusions just yet. Link to post Share on other sites More sharing options...
dfarkas Posted January 23, 2012 Share #34 Posted January 23, 2012 Perhaps I misheard, or Stephan Schulz misspoke. I will seek clarification and post an update. Link to post Share on other sites More sharing options...
pico Posted January 23, 2012 Share #35 Posted January 23, 2012 Pico, you are not an idiot. Any leaf shutter on a SLR camera will still have to work like the Reflex-Compur shutters on the old Contaflexes etc. etc.:[...] Oh, I have a Contaflex (Beta model I think) and the shutter operation is: 0. Operator presses release 1 Lens shutter closes 2. mechanism reduces the lens aperture to the preset (one most of you all forgot) 3. lift the mirror 4. rear flap lifts up (flap protects film from exposure during focusing) 5. Open and close BTL shutter 6. Operator lifts finger from shutter and lens stops back down 7. Depending on model, mirror and rear flap drops. Mine does #7 only upon film advance. Mine has prontor shutter. Only lens I have is 30mm Pantar. Note that the BTL shutter is fixed to the camera and all lenses used the same lens behind the shutter so focal length had no effect upon shutter's operation. (Otherwise longer lenses might have bigger BTL shutters). For a digital SLR and CCD, the shutter would first have to open fully, then the BTL leaf shutter works, CCD transfer goes to buffer. Once buffer transfer is made, the FP shutter and mirror return can begin. The only limitation of shutter is really lag: the time it takes to open the FP shutter's first curtain. Leaf shutters of reasonable sizes are quick enough to actuate and close with almost no practical delay. Smaller shutter is better. At one time there was a small Kodak (I think) that had 1/1000th of a second, but they broke often and were dropped back to 1/500th and were considered somewhat unreliable even at that speed. Link to post Share on other sites More sharing options...
EJohnE Posted January 24, 2012 Share #36 Posted January 24, 2012 I asked on the Fuji X100 Forum re BTL shutter/sensor operation, and Pavig replied as follows: "I believe the x100 is (like most mirrorless cameras) constantly flushing the sensor of data. The shutter is only required to stop new light from entering when an exposure has been made. This is common with CMOS sensor cameras like the Fuji. Some sensor chips of this type don't actually need a shutter at all, and use an electronic switch at the pixel level to cut off the effect of new light. The fuji includes it as the shutter allows for a reduced component count on the sensor, and subsequent decrease in noise during the amplification stage of sensor reading. This translates into better high-iso performance and lower noise. Some other (older, pro or video format) cameras use a CCD sensor. For still photography they a full sensor flush, and traditional film style shutter exposure. This is particularly the case with large sensors like the Leica S2. " If that is correct, it would seem that the only advantage of CCD is its alleged better colour rendering. ....? John. Link to post Share on other sites More sharing options...
mjh Posted January 24, 2012 Share #37 Posted January 24, 2012 That isn’t even entirely true of the X100. While it does use an electronic shutter during live view and video recordings, it relies on a mechanical central shutter for still images. CCD sensors can use an electronic shutter if they are of the interline transfer variety – all the CCDs in compact digicams and video cameras are of this kind. The S2, just like M9, has a full-frame transfer CCD. These sensors devote all the available silicon to capturing light and storing electrons, leaving no space for implementing an electronic shutter. Link to post Share on other sites More sharing options...
stephanjuergenschulz Posted January 25, 2012 Share #38 Posted January 25, 2012 The sequence posted by David Farkas is correct. The sensor needs darkness for readout, but not for starting exposure after first curtain of focal plan shutter has completely opened. Innovative, isn`t it? Link to post Share on other sites More sharing options...
wildlightphoto Posted January 25, 2012 Share #39 Posted January 25, 2012 The sequence posted by David Farkas is correct. The sensor needs darkness for readout, but not for starting exposure after first curtain of focal plan shutter has completely opened. Innovative, isn`t it? Would it be accurate to say the exposure is started electronically once the focal plane shutter is completely open? Link to post Share on other sites More sharing options...
mjh Posted January 25, 2012 Share #40 Posted January 25, 2012 I would assume that the Pulsed Flush Gate is used for draining the charges accumulated in all the sensor pixels, effectively resetting the sensor. Strictly speaking there is no way one could start or stop the exposure electronically. Exposure means there is a stream of photons hitting the sensor pixels, creating free photoelectrons that can be stored in each pixel. As long as the mechanical shutter(s) are open and the sensor is exposed to light, there is nothing to stop or start this process – it just goes on and on. Having said that, one can flush the charges accumulated in all the pixels at once – the sensor of the S2 has a Pulsed Flush Gate for this very purpose. Since it removes all the electrons accumulated up to that time, charge accumulation starts anew. That would be one half of an electronic shutter. Unfortunately there is no useful way of stopping charge accumulation. One could flush the sensor pixels again, but then their contents would go down the drain and the image would be lost. Sensors implementing an electronic shutter effectively freeze the charges accumulated in each pixel by either shifting the charges of each pixel into another pixel that is shielded against light and can be read out at leisure (interline transfer CCDs) or by reading out all the pixels in very fast succession (CMOS sensors with rolling shutter). Neither is supported by the S2’s sensor, though. Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.